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Optical and electronic properties of functional polythiophenes 2009

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Optical and Electronic Properties of Functional Polythiophenes   by   Tamara Katherine Kunz   Hon. B.Sc., Chemistry (Co-op) University of Victoria, 2003     A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF   DOCTOR OF PHILOSOPHY   in   The Faculty of Graduate Studies (CHEMISTRY)     THE UNIVERSITY OF BRITISH COLUMBIA  (Vancouver)   December 2009     © Tamara Katherine Kunz, 2009  ii Abstract The synthesis and characterization of a series of functionalized head-to-tail regioregular poly-3-alkylthiophenes are reported. The influences of the structure and functional groups on the optical and electronic properties are investigated with NMR, absorption, emission and infrared spectroscopy, gel permeation chromatography, and cyclic voltammetry. A regioregular poly-3-alkylthiophene (Poly-1) was synthesized via Grignard Metathesis polymerization conditions. Poly-1 contains bromide groups as sites of latent reactivity along the polymer backbone through which additional reactions were carried out post-polymerization. The bromide was converted to an azide group (Poly-2) which was further functionalized via Click chemistry with a variety of functional groups. Click chemistry was carried out using the Huisgen 1,3-dipolar cycloaddition reaction. Post-polymerization functionalization of Poly-2 provided a facile method for preparing a variety of related functional polymers, each with identical average chain length, average polydispersity and average distribution of monomers. Preparation of Poly-3a, -3b, and -3c, demonstrated the utility of the Click reaction for modifications with a variety of functional groups. A series of poly-3-alkylthiophene analogs (Poly-1 - Poly-11) were characterized by absorption and emission spectroscopies and the spectra were found to be dependant on regioregularity along the polymer backbone. The UV-vis absorption maxima, varied with the percentage of head-to-tail couplings in relation to the extent of conjugation. The series of dithienylethene functionalized oligo- (71) and polymer analogs (Poly-4, Poly-7 and Poly-11) displayed fluorescence quenching capabilities upon  iii photoinduced ring closing of the dithienylethene moiety via energy transfer. The extent of quenching was determined to be dependent on both the length and structure of the backbone. Extended conjugation contributed to amplified fluorescence quenching as observed by complete fluorescence quenching of Poly-4. The functionalization of the Poly-2 with the stable free nitroxide radical 2,2,6,6- tetramethylpiperdine-1-oxyl is described. The resulting polymer, Poly-12, was characterized with cyclic voltammetry and IR spectroscopy. Electrochemical deposition of thin films of Poly-12 onto various working electrodes is described. The thin films were investigated for potential charge storage via galvanostatic charge/discharge cycles. IR spectroscopy revealed that the nitroxide radical had sensitized the polythiophene backbone to oxidation, resulting in irreversible damage to the polymer and reduced charge storage capacity.  Chart 0-1 FeFc = DTE-37 = O S S F FF FF F O N O TEMPO =    iv Chart 0-2  S S R C6H13 x y n R = Br R = N3 R = DTE-37 {x:y; 1:2} Poly-1 Poly-2 Poly-3a Poly-3b Poly-3c R = (CO)OMe S S N N N C6H13 x y n {x:y; 1:2} R R = CH2NH2 R = Fc Poly-4 R = Br R = N3 Poly-5 Poly-6 {x:y; 2:3} S S R C6H13 x y x = 0Poly-8 R = TEMPOPoly-12 S S N N N C6H13 x y n {x:y; 2:3} R R = DTE-37Poly-7 S S C6H13 x y {x:y; 1:10} N N N R R = DTE-37Poly-11 R = Br R = N3 Poly-9 Poly-10 {x:y; 1:10} S N3 S C6H13 S C6H13 R = N3 70 R = DTE-3771   v Table of Contents Abstract ............................................................................................................................... ii  Table of Contents.................................................................................................................v  List of Tables ................................................................................................................... viii  List of Figures .................................................................................................................... ix  List of Charts.................................................................................................................... xiii  List of Schemes................................................................................................................ xiv  List of Equations .............................................................................................................. xvi  List of Symbols and Abbreviations................................................................................. xvii  Acknowledgements........................................................................................................ xxiii  Dedication ....................................................................................................................... xxv  Co-Authorship Statement............................................................................................... xxvi  CHAPTER 1 Introduction..................................................................................................27  1.1 Overview........................................................................................................... 27 1.2 Polymer Fundamentals...................................................................................... 29 1.2.1 Definitions................................................................................................. 29 1.2.2 Polymerization Methods ........................................................................... 31 1.3 Conjugated Polymers ........................................................................................ 33 1.3.1 Electronic Structure .................................................................................. 33 1.3.2 Polythiophene ........................................................................................... 34 1.3.3 Regioregularity ......................................................................................... 36 1.3.4 Synthetic Methods .................................................................................... 38 1.4 Polymer Functionalization ................................................................................ 40 1.4.1 Post-Polymerization.................................................................................. 41 1.4.2 Click Chemistry ........................................................................................ 42 1.4.3 Huisgen 1,3-Dipolar Cycloaddition .......................................................... 43 1.5 Pendant Groups................................................................................................. 44 1.5.1 Dithienylethenes ....................................................................................... 45 1.5.2 Stable Nitroxyl Free Radical: TEMPO..................................................... 50 1.6 Goals and Scope................................................................................................ 53 1.7 References......................................................................................................... 54   vi CHAPTER 2 Synthesis of Random Co-Polythiophenes Using GRIM Polymerization and Functionalization Via Huisgen 1,3-dipolar Cycloaddition .........................................62  2.1 Introduction....................................................................................................... 62 2.2 Experimental ..................................................................................................... 67 2.2.1 General ...................................................................................................... 67 2.2.2 Procedures................................................................................................. 68 2.3 Results and Discussion ..................................................................................... 77 2.3.1 Monomer Synthesis and Spectroscopy ..................................................... 77 2.3.2 Polymer Synthesis and Spectroscopy ....................................................... 79 2.3.3 Monomer Click Reaction and Spectroscopy............................................. 85 2.3.4 Polymer Click Reactions and Spectroscopy ............................................. 88 2.4 Conclusions....................................................................................................... 92 2.5 References......................................................................................................... 93  CHAPTER 3 Synthesis and Characterization of Dithienylethene Modified Oligo- and Polythiophenes...................................................................................................................97  3.1 Introduction....................................................................................................... 97 3.2 Experimental ................................................................................................... 100 3.2.1 General .................................................................................................... 100 3.2.2 Procedures............................................................................................... 101 3.3 Results and Discussion ................................................................................... 114 3.3.1 Synthesis ................................................................................................. 114 3.3.2 NMR spectroscopy.................................................................................. 120 3.3.3 Size Exclusion Chromatography............................................................. 128 3.4 Conclusions..................................................................................................... 130 3.5 References....................................................................................................... 131  CHAPTER 4 Reversible Amplified Fluorescence Quenching of Dithienylethene Functionalized Polythiophene..........................................................................................135  4.1 Introduction..................................................................................................... 135 4.2 Experimental ................................................................................................... 138 4.2.1 General .................................................................................................... 138 4.3 Results and Discussion ................................................................................... 139 4.3.1 Absorption and Emission Studies ........................................................... 139 4.3.2 Fluorescence Quenching and Amplification........................................... 150 4.4 Conclusions..................................................................................................... 158 4.5 References....................................................................................................... 159        vii CHAPTER 5 Electrodeposition of TEMPO Functionalized Polythiophene Thin Films.161  5.1 Introduction..................................................................................................... 161 5.2 Experimental ................................................................................................... 163 5.2.1 General .................................................................................................... 163 5.2.2 Procedures............................................................................................... 165 5.3 Results and Discussion ................................................................................... 166 5.3.1 Synthesis and Characterization ............................................................... 166 5.3.2 Electron Spin Resonance Studies............................................................ 169 5.3.3 Cyclic Voltammetry Studies ................................................................... 170 5.3.4 Capacity and Charge/Discharge Studies ................................................. 175 5.3.5 Backbone Oxidation................................................................................ 177 5.4 Conclusions..................................................................................................... 180 5.5 References....................................................................................................... 181  CHAPTER 6 Conclusions and Future Work ...................................................................185  6.1 General Conclusions ....................................................................................... 185 6.2 Suggestions for Future Work .......................................................................... 187 6.3 References....................................................................................................... 192   viii List of Tables Table 2-1. Absorption and emission data comparisons for Poly-1 and Poly-2 ................ 85  Table 3-1. SEC comparative data for polymer series. .................................................... 128  Table 4-1. UV-vis absorption and emission data from different polymer species ......... 143     ix List of Figures Figure 1-1. Examples of common pi-CPs; polyacetylene (PA, 1), polyaniline (PANI, 2), poly(p-phenylenevinylene) (PPV, 3), polypyrrole (PPy, 4), and polythiophene (PT, 5).......................................................................28  Figure 1-2. Oxidation (p-doping) of 1 with iodine. ..........................................................33  Figure 1-3. Simplified molecular orbital diagram for a CP. .............................................34  Figure 1-4. A schematic representation of (a) rr-HT coupling, with planar arrangement of the thiophene rings, and (b) steric interactions of the alkyl side chains due to HH/TT mis-couplings causing twisting of the PT backbone............................................................................................37  Figure 1-5. Typical UV-vis absorption spectra of photoinduced reaction between two isomers A and B.....................................................................................47  Figure 1-6. Simplified energy diagram for photo-induced ring closing reaction of 1,3,5- hexatriene............................................................................................49  Figure 2-1. 1H NMR spectra of Poly-1 (black), 60 (red), and 63 (green). X = residual CHCl3 in the deuterated solvent. .....................................................82  Figure 2-2. 1H NMR spectra of Poly-1 (black) and Poly-2 (red). X = residual CHCl3 and H2O in the deuterated solvent.....................................................83  Figure 2-3. ATR-IR spectra of Poly-1 (black) and Poly-2 (red). .....................................84  Figure 2-4. 1H NMR spectra isomers 65 (black) and 66 (red). X = residual CHCl3 in the deuterated solvent. ..............................................................................86  Figure 2-5. 1H-1H NMR NOE difference spectrum (red) and 1H NMR spectrum (black) of 65. X = residual CHCl3 in the deuterated solvent. .......................87  Figure 2-6. 1H NMR spectra of 65 (black) and Poly-3a (red). .........................................89  Figure 2-7. Cyclic voltammogram of Poly-3b on a Pt button electrode in dry CH2Cl2 containing 0.1 M [n-Bu4N]PF6. Scanned from +0.2 to +1.2 V vs. SCE, scan rate = 100 mVs-1.....................................................................91  Figure 3-1. Typical absorption spectra of the ring-open (black) and ring-closed (red) isomers of substituted DTE..................................................................98   x Figure 3-2. 1H NMR spectrum 68 dissolved in C6D6 (400 MHz). X = residual C6H6 in the deuterated solvent. ...................................................................121  Figure 3-3. 1H NMR spectra of a C6D6 solution of 68o as a function of irradiation time (a) 0 min, (b) 10 min, (c) 90 min, (d) 145 min (400 MHz). Irradiation with UV-lamp at 302 nm. .........................................................122  Figure 3-4. 1H NMR spectrum of Poly-4 dissolved in C6D6 (300 MHz). X = residual CHCl3 present in the deuterated solvent. ......................................124  Figure 3-5. 1H NMR spectra for Poly-8 (black) and Poly-9 (red) dissolved in CDCl3 (400 MHz). X = residual CHCl3 and water in the deuterated solvent. ........................................................................................................126  Figure 3-6. 1H NMR spectrum of Poly-11 dissolved in CDCl3 (300 MHz). Inset shows the magnified baseline. X = residual CHCl3 in the deuterated solvent. ........................................................................................................127  Figure 4-1. Demonstration of amplified fluorescence quenching along a polymer backbone through binding of a quencher (●) to a receptor ( ).................136  Figure 4-2. (a) Absorption spectra of 68o (black dashed) and 68c (red dashed) and (b) absorption (black) and emission (red) spectra of Poly-2................140  Figure 4-3. UV-vis absorption spectra of a C6H6 solution of Poly-4, with irradiation at 310 nm...................................................................................141  Figure 4-4. Emission spectra of a C6H6 solution of Poly-4, with irradiation at 310 nm. ..............................................................................................................142  Figure 4-5. (a) Absorbance spectra of 68o (black dashed) and 68c (red dashed) and (b) absorbance (black) and emission (red) of 70..................................144  Figure 4-6. (a) UV-vis absorption and (b) emission spectra of the photo-induced ring closing reaction of a C6H6 solution of 71 upon irradiation with a 302 nm lamp. ..............................................................................................145  Figure 4-7. Monitoring the change in absorbance and emission intensity of 71 over 11 ring-opening and ring-closing cycles. Absorbance monitored at 298 nm (), and 595 nm (). Emission monitored at 440 nm (). .............................................................................................................146  Figure 4-8. (a) UV-vis absorption and (b) emission spectra of the photo-induced ring closing reaction of a C6H6 solution of Poly-7 upon irradiation with a 302 nm lamp.....................................................................................147   xi Figure 4-9. (a) UV-vis absorption and (b) emission spectra of the photo-induced ring closing reaction of a C6H6 solution of Poly-11 upon irradiation with a 302 nm lamp.....................................................................................149  Figure 4-10. (a) Absorption and (b) emission spectra of Poly-4 (open: black solid lines, closed: black dotted line) and Poly-2/DTE-37 (open: red solid lines, closed: red dotted line). .....................................................................150 Figure 4-11. Changes in absorbance (λmax = 595 nm) of Poly-4c () and Poly- 2/DTE-37c (), and changes in emission (λmax  = 575 nm) of Poly- 4o () and Poly-2/DTE-37o () upon approaching the PSS. .................151  Figure 4-12. Normalized emission, F/F0 (λmax = 575 nm), as a function of normalized absorbance, A/APSS (λmax = 595 nm), for the C6H6 solutions of Poly-4 () and Poly-2/DTE-37 (). ....................................153  Figure 4-13. Initial induction of fluorescence quenching experienced by Poly-4 with shorter irradiation times.29 ..................................................................154  Figure 4-14. Comparison of amplified fluorescence quenching for Poly-4 (), Poly-2/DTE-37 (), Poly-7 (), Poly-11 () and 71 (). ....................156  Figure 5-1. IR spectra of Poly-12 (green), Poly-2 (red), and 74 (black) displaying the fingerprint region. (*) indicates the ν(NO·) stretching frequency. .......167  Figure 5-2. Absorption and emission spectra of CH2Cl2 solutions of Poly-2 (black) and Poly-12 (red)............................................................................168  Figure 5-3. X-band ESR spectrum of Poly-12 in C6H6 solution at 22 °C. Modulation Frequency: 20.00 kHz. Modulation Amplitude: 0.02 G. Time Constant: 2.56 s. Gain: 60 dB. Sweep Width: 150.6 G. ....................170  Figure 5-4. (a) Initial scan and (b) polymerization of Poly-12 on ITO. 0.1 M [n- Bu4N]PF6 in CH2Cl2 on ITO coated glass working electrodes. Scan rate = 50 mVs-1. ..........................................................................................171  Figure 5-5. Cyclic voltammograms of the growth of Poly-12 vs. Poly-2. 0.1 M [n-Bu4N]PF6 in CH2Cl2 solutions growth on ITO coated glass electrodes. Scan rate = 50 mVs-1 . ................................................................172  Figure 5-6. Degradation of Poly-12 on ITO working electrode. 0.1 M [n- Bu4N]PF6 in  ACN. Scan rate = 100 mVs-1. ...............................................173  Figure 5-7. Cyclic voltammogram of Poly-12 on carbon paper with increasing scan rate (Propylene carbonate, mVs-1): 25, 50, 100, 150, 200. .................174   xii Figure 5-8. Typical galvanostatic charge-discharge curve of Poly-12 scanned at 0.1 mA in propylene carbonate with 0.1 M [n-Bu4N]PF6 supporting electrolyte. Scanned between 0.8 – 1.2 V. ..................................................176  Figure 5-9. ATR-IR spectra of (a) Poly-12 before (black) and after (green) isolation from the CV solution and (b) Poly-12 (black) and Poly-2 (red) isolated from the polymerization reaction..........................................178  Figure 6-1. Schematic of a gated sensor based on DTE photoinduced ring-closing fluorescence quenching in which DTE ( ) can only undergo the ring-closing reaction upon binding of the analyte ( ). ..............................189   xiii List of Charts Chart 0-1 ............................................................................................................................ iii  Chart 0-2 ............................................................................................................................ iv  Chart 1-1 ........................................................................................................................... 29  Chart 1-2 ........................................................................................................................... 30  Chart 1-3 ........................................................................................................................... 35  Chart 1-4 ........................................................................................................................... 37  Chart 1-5 ........................................................................................................................... 40  Chart 1-6 ........................................................................................................................... 50  Chart 6-1 ......................................................................................................................... 190  Chart 6-2 ......................................................................................................................... 191   xiv List of Schemes Scheme 1-1 ....................................................................................................................... 32  Scheme 1-2 ....................................................................................................................... 36  Scheme 1-3 ....................................................................................................................... 39  Scheme 1-4 ....................................................................................................................... 43  Scheme 1-5 ....................................................................................................................... 44  Scheme 1-6 ....................................................................................................................... 45  Scheme 1-7 ....................................................................................................................... 50  Scheme 1-8 ....................................................................................................................... 51  Scheme 1-9 ....................................................................................................................... 52  Scheme 2-1 ....................................................................................................................... 63  Scheme 2-2 ....................................................................................................................... 64  Scheme 2-3 ....................................................................................................................... 66  Scheme 2-4 ....................................................................................................................... 77  Scheme 2-5 ....................................................................................................................... 80  Scheme 2-6 ....................................................................................................................... 86  Scheme 2-7 ....................................................................................................................... 88  Scheme 3-1 ..................................................................................................................... 114  Scheme 3-2 ..................................................................................................................... 115  Scheme 3-3 ..................................................................................................................... 116  Scheme 3-4 ..................................................................................................................... 118  Scheme 3-5 ..................................................................................................................... 119  Scheme 3-6 ..................................................................................................................... 120  xv Scheme 5-1 ..................................................................................................................... 161  Scheme 5-2 ..................................................................................................................... 162  Scheme 5-3 ..................................................................................................................... 166  Scheme 5-4 ..................................................................................................................... 179  Scheme 6-1 ..................................................................................................................... 188  Scheme 6-2 ..................................................................................................................... 190  Scheme 6-3 ..................................................................................................................... 191   xvi List of Equations Mw = DP · Mru      Eq. 1-1.......................................................................................... 30 I−I  →  2 I·         Eq. 1-2................................................................................................ 32 I·  +  M  →  I−M·       Eq. 1-3........................................................................................ 32 I−M·  +  nM  →  I−[M]n−M·      Eq. 1-4 ...................................................................... 32 I−[M]n−M·  +  S  →  I−[M]n−M  +  (S*)    Eq. 1-5 ..................................................... 32 PSS (%) = Beq / Ai × 100     Eq. 1-6 ............................................................................... 48 A* + Q  A + Q      Eq. 4-1........................................................................................ 152 A* + Q  A + Q*     Eq. 4-2....................................................................................... 152 ( ) ( )1000MW3600/ × × = eNkgAhC A                                    Eq. 5-1............................. 175   xvii List of Symbols and Abbreviations Abbreviation Description α methylene group; directly attached to aromatic ring A Ampere; chromophore: generic ring-open isomer (DTE)  Ai initial concentration of open isomer (DTE) ACN acetonitrile AFM atomic force microscopy AFP amplified fluorescent polymer ATR attenuated total reflectance β methylene group; once removed from aromatic ring B generic ring-closed isomer (DTE) br broadened (NMR) BDE bond dissociation energy BPP bis(p-phenylene)-34-crown-10 Beq equilibrium concentration of closed isomer (DTE) χ methylene spacer (DTE) c ring closed isomer C Coulomb (A s) °C degrees Celsius cm-1 wavenumber (IR) CP conjugated polymer Co-op Cooperattive  Education  xviii CV cyclic voltammetry Calcd calculated δ chemical shift (ppm) d doublet (NMR) dB decibel dd doublet of doublets (NMR) dppe diphenylphosphinoethane dppp diphenylphosphinopropane DMF N,N-dimethylformamide DP degree of polymerization w weight average degree of polymerization DTE dithienylethene ε molar absorptivity (L mol-1 cm-1) e electron charge Ered peak potential, reduction process (V) EI electron impact ESI electrospray ionization ESR electron spin resonance EtOAc ethyl acetate φ methyl groups (DTE) Φ quantum yield F Farad (A s V-1); fluorescence intensity measured at time t Fc ferrocene  xix FET field effect transistor FT Fourier transform G Gauss GHz gigahertz GRIM Grignard Metathesis h hour h Planck’s constant HPLC high-pressure liquid chromatography HOMO highest occupied molecular orbital HH head-to-head HR high resolution HT head-to-tail Hz Hertz i- iso: equal I quantum spin-spin coupling constant I· initiator ITO indium tin oxide J NMR coupling constant (Hz) ko heterogeneous rate constant kex self exchange rate constant kHz kilohertz kJ kilojoules λmax  wavelength at band maximum (nm)  xx L- left handed enantiomeric form LCD liquid crystal display LUMO lowest unoccupied molecular orbital m multiplet (NMR) M molarity (mol L-1); molecular weight of molecule (MS) M monomer M+ molecular ion Mru molecular weight of the repeat unit n number average molecular weight Mw molecular weight w weight average molecular weight MW equivalent mass of polymer (g) m/z mass-to-charge ratio mA milliampere MHz megahertz min minute mmol millimole mol mole MS mass spectrometry mV millivolts ν frequency n number n- normal  xxi NA Avrogadro’s number NBS N-bromosuccinimide NOE nuclear overhauser effect NR nitroxyl radical Nu nucleophile o ring open isomer o- ortho: arene substitution pattern, next to each other OLED organic light emitting diode OPV organic photovoltaics p- para: arene substitution pattern, opposite from each other P3AT poly(3-alkylthiophene) P3HT poly(3-hexylthiophene) PA polyacetylene PANI polyaniline PDI polydispersity index PPE poly(phenylene ethynylene) ppm parts per million PPV poly(p-phenylenevinylene) PPy polypyrrole PSS photostationary state PT polythiophene PTI  Photon Technology International Q quencher  xxii R generic chemical moiety / end group R· neutral radical R+ oxidized radical / cation R- reduced radical / anion Rf retention factor rr regioregular r.t. room temperature s second; singlet (NMR) S* activated species from chain transfer SAM self assembled monolayer SCE saturated calomel electrode SEC size exclusion chromatography S/N signal-to-noise θ twist angle departure from coplanarity t triplet (NMR) t- tertiary TEMPO 2,2,6,6-tetramethylpiperdine-1-oxyl THF tetrahydrofuran TLC thin layer chromatography TT tail-to-tail V Volt vis visible  xxiii Acknowledgements First and foremost, I have to thank my supervisor Dr. Mike Wolf. Thank you for giving me an option when things were uncertain and thank you even more for standing behind my decision to finish what I started. You gave me the opportunity to prove something to myself, and for that I am forever thankful. I would like to extend my appreciation to Dr. Colin Fyfe for reading this thesis in its entirety. On that note, I am also especially grateful to Marek Majewski, without whom, I may never have shown a chapter to Mike. Thank you for reading my entire thesis, some chapters twice, and always with thorough and thoughtful editing. I am indebted to you. I would like to thank all members, past and present, of the Wolf and MacLachlan groups. It has been such a pleasure to work with such a warm, intelligent and entertaining group of people. It will be hard to leave such a fantastic work environment. Some days, it was definitely the people that I came into work for. This thesis would have never been possible without the help and guidance that I received from the chemistry support staff. In particular, David Wong, for weighing out multiple samples of carbon paper, with the promise that this was the last time, only for me to show up again the following week; Brian Ditchburn, for repairing the electrochemistry cell, time and again after I broke it; and finally, Zorana Danilovic, for laughing at me when caught talking to myself. I would also like to thank all members of chemistry acquisitions, the mechanical shop, electronics, and secretarial staff for the help and humour that they provided to me during the course of my work here at UBC. A special thank you goes to both Prof. Neil Branda and Dr. Jeremy Finden, my collaborators on the DTE project. Thank you for all of the thoughtful discussions and  xxiv hard work that made that project come to light.  I must also thank Prof. Steven Holdcroft for the use of his SEC instrument, and thank you to UBC for funding.  Acknowledgments must also be made to Dr. Peter Wassell and Angelo Ariganello for believing in my teaching abilities. The encouragement and opportunities I have received from you both will never be under appreciated. To all of my friends, I count myself blessed because I have too many to mention individually. I hope you all know that this thesis would never have been possible without the support and laughter that I gained from each and every one of these friendships. That being said, there are a few names that I must mention: Agostino Pietrangelo, Toby Astill, and Marek Majewski. Thank you all for the ‘tough love’. To my closest girlfriends, Elektra Jordan and Sylvia Lymburner, I can never thank you enough, just for being there.  My final words of appreciation go to my family. This trip has not been smooth sailing and I cannot thank them enough for being, at the same time, both my shoulder to cry on, and my legs to walk on (literally) during the last six years. To Cindy, Lee, and my beautiful new niece, Jorja, thank you for helping me find my smile. To the Jordans, my extended family, thank you for providing me with a home away from home. And to my wonderful, supportive, and loving parents, Fred and Wendy, thank you for EVERYTHING.  xxv Dedication   To my family at Mahony & Sons.  xxvi Co-Authorship Statement A version of Chapter 2 will be submitted for publication. Kunz, T. K.; Stott, T. L.; Wolf, M. O., Functionalized Polythiophenes via “Click Chemistry”. The work presented in this chapter was done in collaboration with Dr. Tracey L. Stott, at the University of British Columbia. I am the principal investigator and primary author of this work under the supervision of Prof. Michael Wolf. Compounds 60 and Poly-1 were both prepared by Dr. Tracey L. Stott. A version of Chapters 3 and 4 has been published. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Adv. Mater. 2008, 20, (10), 1998-2002. The work presented in these chapters was done in collaboration with Prof. Neil R. Branda and Dr. Jeremy Finden at Simon Fraser University. I was one of the principal investigators and primary authors of this work under the supervision of Prof. Michael O. Wolf. Dr. Jeremy Finden, contribution to this work includes: (1) the synthesis of DTE-37, (2) the absorbance and emission studies of the C6H6 solution of precursors Poly-2/DTE-37, (3) the rate data of Poly-4 and Poly-2/DTE-37, (4) the shorter irradiation time experiment of Poly-4, and (5) collaborative efforts towards quantum yield (Φ) measurements of Poly-4 and Poly- 2/DTE-37. A version of Chapter 5 will be submitted for publication. Kunz, T. K. and Wolf, M. O., Electrochemical Thin Film Deposition of TEMPO Functionalized Polythiophenes. I am the principal investigator and primary author of this work under the supervision of Prof. Michael Wolf.   27 CHAPTER 1 Introduction 1.1 Overview In October of 2007, Sony® introduced a new state-of-the-art flat screen OLED (organic light emitting diode) television.1,2 The OLED technology in this TV is based on emission from small organic molecules sandwiched between two conductive plates and demonstrates the ultimate goal of commercial application for thin-film organic devices. The 3-mm thick screen boasts unparalleled picture quality with an amazing contrast ratio (1,000,000:1), outstanding brightness, exceptional colour reproduction, and a rapid response time when compared to liquid crystal display (LCD) technology. The interest in marrying small organic molecules, and in particular, conjugated polymers (CPs), with inorganic semiconductor technology stems from a variety of promising benefits. As successfully predicted by Moore’s law over the past few decades the number of components on an integrated circuit will double every one to two years.3,4 At this rate, a fundamental size regime limit of solid state integrated circuitry will be reached. A significant benefit offered by organic materials is the ability to move beyond this limit into nanometer scale electronics. Soluble organic polymers open the possibility of depositing thin organic films on a variety of very-low-cost substrates (glass or plastic) through an assortment of innovative processing techniques (spin coating,5,6 stamping,7 and ink-jet deposition8-10). Such films can be processed at room temperature, over large areas, into desired shapes and with optical quality. The ease of polymer processing offers potential for large cost-savings in comparison to traditional semiconductor technology. Additionally, organic compounds can be synthetically engineered to tailor and optimize  28 the desired functions and properties that are useful in electronic devices. Thus, research relating to CPs is almost exclusively dedicated towards electronic applications such as OLEDs,11-13 field effect transistors (FETs),14-16 organic photovolatics (OPV),17-19 and sensors.20,21 CPs (Figure 1-1), also referred to as 'synthetic metals',22,23 are polymers that possess the electronic, magnetic and optical properties of a metal while retaining the mechanical properties and processibility commonly associated with conventional polymers.  Specifically, the materials’ ability to conduct electricity, stability observed upon partial oxidation or reduction (doping), and strong absorption (and emission) in the UV-vis spectrum are features observed because of the delocalization of pi-electrons.23-25 NH N H nn n S n 1 2 3 4 5 n  Figure 1-1. Examples of common pi-CPs; polyacetylene (PA, 1), polyaniline (PANI, 2), poly(p-phenylenevinylene) (PPV, 3), polypyrrole (PPy, 4), and polythiophene (PT, 5).  The extent of delocalization of the pi-electrons is known to be strongly dependent on the coplanarity of the conjugated system.26,27 Understanding the influence of substituents on this structural characteristic is an essential facet in the study of the structure-property relationships in CP materials. The aim of this work was to prepare pi- CPs with defined backbone structure and to investigate the influence of different functional groups on the optical and electronic properties. This thesis describes the synthesis and characterization of regioregular poly(3- alkylthiophenes) (rr-P3ATs) prepared under Grignard Metathesis (GRIM) polymerization conditions. These polymers are prepared with latent functionality to allow post-  29 polymerization modification through the employment of Click chemistry. The effect of the side groups on the polymer properties, as well as the utility of this approach is discussed. Potential applications of these materials arising from the displayed characteristics are also considered. 1.2 Polymer Fundamentals 1.2.1 Definitions Polymers are macromolecular structures that consist of a minimum of several hundred covalently linked atoms and have molecular weights above 103 g mol-1.28 A polymer is also defined as a substance that consists of multiple repetitions of one or more species. These species may be atoms or groups of atoms which are individually referred to as constitutional or repeat units. When the number of repeat units within a chain is low, from two (dimers) up to approximately seven (heptamers),29-31 the resulting structures are referred to as oligomers (Chart 1-1). The term monomer refers to the unreacted species from which the polymer is derived. Chart 1-1 n monomer dimer trimer polymer oligomers n> - 5   Synthesis of a polymer rarely results in molecules of identical structure. Instead, mixtures of macromolecules are obtained that contain similar structures but differ in degree of polymerization (DP). The degree of polymerization is a measure of how many  30 monomer units are incorporated into the polymer chain and can be related to the molecular weight (Mw) according to Eq. 1-1, where Mru is the molecular weight of the repeat unit. Molecular weight is important because it determines many of the physical properties.32,33 These mixtures are referred to as polydisperse with Gaussian distribution and as a result, the values of  DP and Mw are generally reported as average values w and w.  Mw = DP · Mru      Eq. 1-1  Polymer backbones that consist of a single type of repeat unit are termed homopolymers. When a polymer is synthesized from two or more different types of monomers, they are referred to as copolymers. Additional distinctions are made according to the spacial arrangement of monomers within the backbone. This arrangement includes the forms: (a) alternating, (b) random, and (c) block copolymers (Chart 1-2). Chart 1-2 a) b) c) A A A   31 1.2.2 Polymerization Methods In general, polymerization reactions afford high molecular weight chains of repeat monomer units. Depending on the nature of the reactive site on the monomer unit, these chains may be linear, branched, or cross-linked. The chemical process of chain elongation occurs by two main mechanisms; chain growth or step growth.34  Chain Growth Polymerization There are three main steps through which a chain growth polymerization reaction proceeds. These steps are referred to as the initiation (Eq. 1-2 and Eq. 1-3), propagation (Eq. 1-4) and termination steps (Eq. 1-5). Initiation occurs with the addition of an initiator (I·) or activated species that adds to a monomer (M) in such a way that the monomer becomes the new activated center that is able to react further (Eq. 1-3). The activated species is usually generated as the result of a homolytic bond cleavage from a metal complex, or from strongly polar (or ionic) molecules to form two radicals (Eq. 1- 2). The chain growth proceeds as a cascade reaction (Eq. 1-4), where the number of growing chains is directly related to the concentration of initiators in the reaction mixture. Chain growth will proceed until the reactive centers have been terminated or a transfer step has occurred (Eq. 1-5). In a chain transfer reaction, the active center is transferred to a new species (S*) (solvent, initiator, monomer, etc.) that can polymerize further, while resulting in termination of growth for the original polymer chain. Chain growth reactions are characterized by the immediate formation of high molecular weight species and the reaction time generally has no influence on the average molecular weight, only the yield.  32 I−I  →  2 I·         Eq. 1-2 I·  +  M  →  I−M·       Eq. 1-3 I−M·  +  nM  →  I−[M]n−M·      Eq. 1-4 I−[M]n−M·  +  S  →  I−[M]n−M  +  (S*)    Eq. 1-5  Step Growth Polymerization In a step growth mechanism, there is no cascade reaction and there is no need for an activated center to initiate or progress the reaction. Instead, the monomers are linked together via conventional organic synthetic methods such as the formation of an amide linkage via the reaction of an ester and amine (Scheme 1-1). In these reactions, the monomers must contain two functional groups, which may be the same or complementary functionality, in order for polymerization to occur. Step growth is dependant on the sequential collisions/reactions of these complementary groups. In a reaction between two different monomers, stoichiometry is crucial for obtaining high molecular weight species. The mechanism of a step growth reaction is characterized by the immediate formation of low molecular weight species (dimers, trimers, etc.), followed by longer oligomers and towards the end of the reaction time, high molecular weight polymers. Scheme 1-1 CO2CH3H3CO2C NH2H2N H3CO2C O H N H2N CO2CH3 + H2N O H N CO2CH3 n NH2 a) b) + CH3OH + CH3OH   33 1.3 Conjugated Polymers 1.3.1 Electronic Structure Conjugated polymers (CP)s are known to be electrically insulating, or at best semiconductors in their undoped state.23 The discovery by Heeger, MacDiarmid and Shirakawa, which demonstrated that oxidatively doped polyacetylene (PA) (1, Figure 1-2) displays up to 12 orders of magnitude increase in conductivity relative to undoped PA35 sparked the increased interest in CPs for electronic applications. 3 I2 I3 - I3- 1 6  Figure 1-2. Oxidation (p-doping) of 1 with iodine.  The characteristic feature of a CP is the alternating single and multiple (double or triple) bonds along the polymer backbone leading to an extended pi-electron system. PA, the prototypical conducting polymer, has the molecular formula (-CH=CH-)n with two pi- electrons per formula unit, implying a metallic state.35 True PA has localized pi-electrons as a result of Peierls instability leading to alternate single and double carbon-carbon bonds.24,25 The localization resulting from lattice distortions removes the degeneracy of the pi-orbitals, splitting them into pi and pi* bands. Since each band can hold 2n electrons, the pi band is filled and the pi* band is empty. Displayed in the simplified molecular orbital diagram of the valence pi-orbitals (Figure 1-3), increasing the number of repeat units increases the number of orbitals and results in bringing the HOMO and LUMO energy levels closer together. An infinite chain, representative of a CP has a molecular  34 orbital diagram that resembles that of a semiconductor; it consists of a continuum of energy levels which form both a conduction band and a valence band. The energy difference between the highest occupied state (HOMO) and the lowest unoccupied state (LUMO) is the pi−pi* energy gap, or band gap. n = 1 n = 2 n = 4 n = Energy HOMO LUMO Band Gap Conduction Band Valence Band 8 n  Figure 1-3. Simplified molecular orbital diagram for a CP.  1.3.2 Polythiophene Analogous in structure to cis-polyacetylene (7, Chart 1-3), poly(heterocycles) (8, Chart 1-3) are stabilized by the presence of a heteroatom such as sulfur, nitrogen or oxygen. The additional stabilization compared to 7, results from a non-degenerate ground state corresponding to two energetically non-equivalent resonance structures, aromatic  35 and quinoidal (Chart 1-3)36 In particular, PT (PT) (5, Figure 1-1) is one of the most extensively studied CPs.37 With exhibited structural versatility, PT also has a relatively high environmental stability in both the doped and undoped states. There have been reports of synthesized PT displaying conductivity values as high as 103 S cm-1 12 and as such, PT is actively investigated for its conductivity, electrochemistry, and optical properties for material applications38 (electrode materials, electrochromic devices and energy storage). Chart 1-3 X X X X X X X = NH, O, S 7 8 aromatic quinoid   Early syntheses of unsubstituted PT produced polymers with low solubility and processibility, contributing to difficulties in full characterization of the prepared material. Attachment of a flexible alkyl side chain to the conjugated backbone in the 3-position was demonstrated to improve solubility and enhance processability.39 Additionally, it has been identified that effective conjugation is a crucial parameter in achieving high electrical conductivity.40-42 Extended pi-conjugation in PT is only possible when the repeat units are 2,5-linked.43 Since thiophene monomers can couple at the α-(2/5-) or β- (3/4-) positions (Scheme 1-2), introduction of side chains at the 3-position also produced a decrease in the number of α−β mis-couplings (11).44,45  36 Scheme 1-2 SSS α β α α coupling SSS S α β coupling SSS S9 10 11 S S   1.3.3 Regioregularity With the incorporation of alkyl substituents at the 3-position, the asymmetry of the thiophene monomer leads to three regioisomers upon coupling. As displayed in Chart 1-4, head-to-tail (HT), head-to-head (HH) and the corresponding tail-to-tail (TT) orientations are possible. Alkyl chains influence thiophene rotation along the chain; HH and/or TT interactions create sterically driven twisting of the polymer backbone. This disrupts the effective conjugation length of a CP as orbital overlap varies approximately with the twist angle (θ) departure from coplanarity.26,27,46,47 Clearly, HT couplings lead to the most favourable trans-coplanar arrangement of the thiophene rings to minimize gauche interactions and a higher degree of conjugation (Figure 1-4).      37 Chart 1-4 S R S R S R TailHead S R S R HT HH S S RR TT     S SS S SS S S S S a) b) θ θ  Figure 1-4. A schematic representation of (a) rr-HT coupling, with planar arrangement of the thiophene rings, and (b) steric interactions of the alkyl side chains due to HH/TT mis- couplings causing twisting of the PT backbone.     38 1.3.4 Synthetic Methods The synthesis of P3AT is carried out via one of three general methodologies: electrochemical oxidation, chemical oxidative polymerization, or metal catalyzed cross- coupling of 2,5-dihalo-3-alkylthiophenes. The most straightforward method of polymerization is chemical oxidation of 3-alkylthiophene monomers through oxidants such as FeCl3.48,49 This technique generally produces a significant number of regiochemical defects, such as α-β couplings, and is appropriate only when the regioregularity is of no concern. One example of regio-control employing chemical oxidation was demonstrated with the slow addition of FeCl3 to 3-(4- octylphenyl)thiophene.50 Electrochemical routes provide a convenient and controllable way to prepare thin films on a conducting surface. Electrochemical polymerization (Scheme 1-3) is proposed36,51 to proceed via the coupling of two radical cations (13) generated by oxidation of a thiophene monomer (12). Rearomatization of the bithiophene intermediate is the driving force to the dihydro dimer (15). The dimer, with lower oxidation potential, is more easily oxidized and now undergoes coupling with 13. The electropolymerization continues with subsequent addition of 13 until the polymer precipitates onto the electrode surface due to its insolubility in the electrolytic solution. Electrochemical polymerization of a number of 3-alkylthiophenes, including 3-methylthiophene and 3-ethylthiophene results in fewer α−β linkage defects than found through chemical oxidation reactions, but the polymers obtained have regiorandom structure.  39 Scheme 1-3 S S S - 2 H+ SSS H H S S S H - e- S S- 2 H+S SH H SS - e- 13 14 15 161718 12 S R R R R R R R RR R R R RRRR   The high stability of thiophene provides easy access to multiply substituted thiophenes and tolerance to a variety of cross-coupling reactions. Traditionally, transition metal catalyzed cross-coupling reactions did not lend themselves to regioselective polymerization.52,53 A few representative examples that achieve regioregularities close to 100% HT coupling are based on the selective formation of an organometallic group at the α-position of the thiophene ring. McCullough et al.54 developed a synthesis based on the regiospecific lithiation of 2-bromo-3-alklthiophene at the 5-position followed by metal exchange to form the Grignard reagent. Polymerization follows with the addition of Ni(dppp)Cl2 (dppp = diphenylphosphinopropane) as the catalyst. Independent studies by Rieke et al.55 developed a methodology that forms the regiospecific organozinc compound by reaction of dibromo-3-alkylthiophene with highly reactive Zn0, which is subsequently polymerized with a Ni(dppe)Cl2 (dppe = diphenylphosphinoethane) catalyst. Additionally, McCullough et al.56 developed a more general synthesis towards rr-P3AT. This method, known as GRIM polymerization, depends on the regiospecific  40 generation of the Grignard reagent, 2-bromo-5-(bromomagnesio)-3-alkylthiophene, from the dibromo starting material. Polymerization is carried out in situ using the Ni(dppp)Cl2 catalyst .  These methods and others are discussed in greater detail in Chapter 2. 1.4 Polymer Functionalization The initial reason for the incorporation of side chains, and in particular, flexible hydrocarbon chains, onto a PT backbone was to improve polymer solubility. However, it was also observed that the electron donor properties of the alkyl substituent lowers the oxidation potential of the monomers and increases the stability of the resulting polymer to overoxidation.57 Longer alkyl substituents (beyond 7-9 carbons) also strongly influence the co-planarity of the molecules, leading to an increase in mean conjugation length and electrochemical reversibility.56,58 In general, variation of the ratio, electronics and size of the side groups help to tailor and tune the electronic and optical properties of the polymer in combination with the structural modifications. This can be demonstrated with a simple comparison between poly-(3-isobutyl)thiophene (19) and poly-3- butylthiophene (20) (Chart 1-5). The bulky, branched structure of the isobutyl side chain induces a coil like structure in solution making it quite soluble, however, this produces a deleterious break in conjugation and a corresponding blue shift in peak absorption compared to 20.59 Chart 1-5 S S 19 20   41 1.4.1 Post-Polymerization An ongoing research goal has been the reduction of the energy bandgap of the CP.60 A smaller bandgap should facilitate the ease of doping, improve photoconductivities, and is likely to afford material that would be transparent in the doped state. The most direct approach towards this goal is by the covalent grafting of functional groups onto the monomers prior to polymerization. This requires a detailed comprehension of the effects of substitution (inductive or steric) on the monomer for subsequent reaction. For instance, while strong electron-withdrawing groups on the thiophene monomer will lower the LUMO, effectively reducing the bandgap, this raises the oxidation potential and prevents electropolymerization.45,61 It is also important for the functionality of the monomer to remain compatible with the polymerization conditions. Grignard reagents are incompatible with alcohol functional groups and as a result, protection of such side groups is required during polymerization, potentially adding steps to the synthetic procedure.62,63 An alternate method to prepare polymers bearing functional pendant groups is to incorporate latent functionality into the polymer backbone, which can be modified post- polymerization.64-66 In addition to removing potential complications during polymerization, this provides a facile method to generate a series of related polymers bearing a diverse library of functionality. The ability to perform these modifications via ‘simple’ chemical reactions (i.e. reactions that do not require complex work-up or purification) is highly desirable. “Click” reactions, a moniker coined by Sharpless et al.,67 are a family of reactions that are powerful in their simplicity and utility for chemical modifications.  42 1.4.2 Click Chemistry Click reactions have been used extensively in a broad spectrum of applications such as surface engineering, synthesis of macromolecular structures, and in the modification of biological molecules.68,69 However, in order to be deemed a Click reaction, a stringent list of criteria must be met.67 The reaction must give quantitative yields (100% product). They must have high functional group tolerance (avoiding protecting group strategies), and generate only inoffensive by-products which can be easily removed with non-chromatographic techniques. Reaction conditions must be simple; ideally insensitive to oxygen and water, be carried out in all solvents irrespective of their protic/aprotic or polar/nonpolar nature, require readily available starting materials and reagents, and be carried out at ambient temperature. There are four broad classes of reaction that fit the Click chemistry paradigm (Scheme 1-4). These include (a) cycloadditions; 1,3-dipolar cycloaddition and the Diels- Alder [4+2] cycloaddition, (b) nucleophilic substitution/ring opening reactions, (c) carbonyl chemistry of the 'non-aldol' type, and (d) addition to carbon-carbon multiple bonds. In each of these reactions, the driving force is a thermodynamic gain of usually greater than 84 kJ mol-1.67 The reagents of a Click reaction are necessarily highly reactive, but have very narrow reaction trajectories, that is, they produce a single product with high yields and exclusive stereospecificity.  43 Scheme 1-4 O R' R" O- Nu R" R' Nu- R2 R1 R1 OHHO R2 21 22 23 24 27 28 a) b) c) d) R H O R" O NH2 O R" O N O R H 25 26 +   1.4.3 Huisgen 1,3-Dipolar Cycloaddition The Huisgen 1,3-dipolar cycloaddition70,71 (the reaction between a terminal alkyne (29) and an azide group (30), Scheme 1-5), has emerged as the method of choice among the many available types of Click reactions. This reaction is a pure fusion reaction, meaning the molecular formula of the product is the combined formulae of the reactants.  While there are concerns about the explosive nature of the azide moiety,72,73 it is ideal for standard organic synthesis because of its inactivity towards a wide variety of conditions and reagents74 rendering it ‘invisible’ and preserving it through a reaction sequence until needed. Furthermore, the triazole ring is a thermally and hydrolytically stable conjugated linkage.75,76  44 Scheme 1-5 N N N R2 N N N R1 R2 1,4-triazole + CuI N N N R1 R2 1,5-triazole major minor 29 30 31 32 H R1 +  Initial studies of the cycloaddition between aryl/alkyl azides and strongly activated alkynes proceeded at moderate temperatures reaching yields of 90-100%.67,77,78 Further to the purely thermal process, it was discovered that CuI salts accelerated the cycloaddition reaction to result in quantitative yields at 25 °C.79 Finally, it was observed that the formation of the 1,4-triazole (31) was regioselectively preferred through a CuI catalyzed Huisgen reaction between non-activated alkynes and aryl/alkyl azides (Scheme 1-5).80 1.5 Pendant Groups Molecules that respond to external stimuli such as light, electricity, or chemical reagents are potentially useful for application in organic electronic devices.81 The use of light (photons) and electricity (electrons) are particularly promising stimulants. They can influence a system response without any extraneous waste (by-products from chemical reactions), they behave as stoichiometric triggers, and can be focused to localized areas without affecting the surrounding area. In the two next sections, two molecular moieties will be described and their desirable properties with application towards modification of the CP will be outlined. In this thesis, a light activated switch (dithienylethene (DTE)) and a redox active group (2,2,6,6-tetramethylpiperdine-1-oxyl (TEMPO)) are both investigated for their influence on a rr-P3AT.  45 1.5.1 Dithienylethenes Compounds that change colour and reversibly interconvert between two isomers upon the absorption of light, in which each isomer displays unique absorption spectra, are classified as photochromic compounds.82 There are several main classes of organic photochromic compounds including spiropyrans (33→34), azo compounds (35→36) and fulgides/fulgimides (37→38) (Scheme 1-6). In particular, dithienylethene (DTE, 39→40) is a commonly studied photochromic compound that displays thermal irreversibility. DTE and its derivatives display a colouration/decolouration fatigue resistance of more than 104 cycles, in addition to their thermal stability, making them highly appealing for applications to molecular electronics.83,84 Scheme 1-6 N O NO2 N NO2 O X O O O X O O O X = O (fulgides) X = NR (fulgimides) N N N N R S S F F FF F F R R S S F F FF F F R 33 34 hν1 hν2 or ∆ 35 36 37 38 39 40 hν1 hν1 hν1 hν2hν2 hν2 or ∆    46 In general, irradiation of an open isomer (A) with one wavelength (hν1) will induce a photoisomerization reaction to produce a closed isomer (B).85 The reverse reaction is accomplished by irradiating B with a different wavelength (hν2). The wavelengths of irradiation are dependant on the absorption spectra of the two isomers. Ideally, the two isomers, A and B, would absorb light in well separated regions of the absorption spectrum, allowing for the independent irradiation of each compound. Frequently, however, the two isomers have absorption bands in the same region of the spectrum where light is used to induce one of the photochemical transformations. As seen in a typical absorption spectrum (Figure 1-5), irradiation of isomer A with hν1 results in a decrease of A’s absorption band and the corresponding increase of the absorption band of isomer B located in the visible region of the spectrum. It can be observed that formation of isomer B does not fully reduce the absorption in the region up to approximately 350 nm.  47 300 400 500 600 700 800   Wavelength (nm) R' S S F FFFF F R'' hν1 hν2 A B R' S S F FFFF F R'' Ab s o rb a n c e  Figure 1-5. Typical UV-vis absorption spectra of photoinduced reaction between two isomers A and B.  Irradiation into this region of spectral overlap (~ 350 nm) results in two competing photoisomerization reactions (i.e. A → B and B → A), and sets up an equilibrium between the forward and reverse reactions. The point at which the equilibrium is reached is termed the photostationary state (PSS).86 The PSS can be calculated by determining the amount (or concentration) of isomer B at equilibrium (Beq) in relation to the initial amount (or concentration) of isomer A (Ai) and is usually reported as a percentage according to Eq. 1-6. The equilibrium between the two isomers,  48 and therefore the PSS, is governed by the quantum yields (Φ) of the forward and reverse reactions, the concentrations and the molar absorptivities (ε) of the two isomers at the irradiation wavelength.  PSS (%) = Beq / Ai × 100     Eq. 1-6  The backbone of DTE is based on a 1,3,5-hexatriene moiety. According to the Woodward-Hoffmann87 rules of pericyclic reactions, a system with 4n + 2 pi-electrons will ring close in a conrotatory fashion from the excited state and in a disrotatory fashion from the ground state. The relative ground state energy differences between the open and closed states of a disrotatory ring closure are very large. This energy difference practically prohibits cyclization from the ground state. There is no large energy barrier between the open and closed states of a conrotatory ring closure, ensuring that cyclization will only occur from the excited state. The frontier molecular orbitals of the hexatriene system are shown in Figure 1-6. Absorption of light promotes an electron from the HOMO to the LUMO and based on the symmetry of the excited state, the ring closing reaction must occur in a conrotary fashion.84,88   49 HOMO LUMO Conrotary Ring Closurehν Ring-closed ProductGround State Excited State En er gy  Figure 1-6. Simplified energy diagram for photo-induced ring closing reaction of 1,3,5- hexatriene.  The stability of the photo-generated product depends on the energy barriers associated with the cycloreversion reaction. If the energy difference between the open and closed isomers is large, the reaction barrier becomes small and the reaction readily takes place. However, if the energy difference between the open and closed isomers is small, the reaction barrier is large and the cycloreversion is not expected to occur. The ground state energy difference is related to the aromaticity change between the open and closed isomers (Scheme 1-7). The energy difference between 43 and 44 is determined to be ~ 2 kJ mol-1 which is one of the lowest aromatic stabilization energies.84,88 These energy considerations demonstrate the thermal irreversibility of ring opening/closing in DTE.  50 Scheme 1-7 S S 43 44   1.5.2 Stable Nitroxyl Free Radical: TEMPO Since the first example of a stable organic nitroxyl radical (NR) was prepared by Piloty and Schwerin,89 a variety of NRs have been prepared (Chart 1-6).90 Besides the parent compound (45), NRs bearing primary, secondary, and tertiary alkyl groups, aryl, alkoxy and amino groups are all known. The characteristic feature of a NR is the presence of a single unpaired electron delocalized over an N-O group, conceived as the superposition of two resonance structures. Chart 1-6 N NH NH HN H3C H3C O N O N ON R R O NR ONO 45 R = H 46 R = t-Bu 47 R = CF3 48 R = C5H6 49 50 51 52 N R R O    51 Several NRs demonstrate remarkable stability.90 They do not decompose over long periods of time, do not show any tendency to dimerize, and persist in both polar and non-polar solvents to form brightly coloured solutions. The absence of α-hydrogen atoms is an essential element with regards to the observed stability. The presence of one or more α-H atoms will allow disproportionation of the species to the hydroxylamine (54) and the corresponding nitrone (55) (Scheme 1-8). Scheme 1-8 R N O H R N OH H R N O +2 555453   The relative stability of these radicals can also be explained based on several thermodynamic parameters. The energy of delocalization of the unpaired electron over the N-O bond has been estimated at ~ 125 kJ mol-1 for heterocyclic NRs.91 The N-OH bond dissociation energy (BDE) of the parent hydroxylamine is also considered a key characteristic in accounting for the stability of the obtained radical. In particular, TEMPO (49, Chart 1-6), has been reported to have a BDE of 292 kJ mol-1.92 To quantify this value, the ability of TEMPO to affect hydrogen abstraction would be highly endothermic based on the determined BDE. As a result of this unprecedented stability, TEMPO radicals are in practical use to monitor/mediate redox reactions93,94, antioxidants,95,96 and as charge transfer salts with 1,4-benzoquinone derivatives.97 The TEMPO radical has also been heavily investigated for its rich electrochemistry and remarkably fast electrode kinetics. The neutral radical can be both  52 oxidized (p-doped) and reduced (n-doped) via rapid, reversible and stoichiometric 1e- transfer processes (Scheme 1-9). For example, the TEMPO/TEMPO+ redox couple displays a hetero-geneous rate constant of k0 = 8.4×10-1 cm s-1 and an electron self exchange rate of kex ~ 108 M-1 s-1 in solution.98,99 The impressive rate of electron transfer is accounted for by very little structural change coupled with the available flexibility of the six-membered ring.100 These properties of the TEMPO radical have generated considerable interest for applications in organic based batteries.100-103 Scheme 1-9 N O R N O R N O R + e- - e- nitroxyl radical 56 49 57 + e- - e- p-doped n-doped    53 1.6 Goals and Scope The goals of this thesis are: (1) to synthesize HT rr-P3AT, (2) to functionalize the prepared polymers post-polymerization, and (3) to investigate the electronic and optical properties of these functionalized polymers for possible materials applications. The first goal of this study was to prepare PT copolymers with HT regioregularity via GRIM polymerization conditions, to ensure optimal conjugation along the polymer backbone. Using variations of the GRIM conditions, different copolymer backbone motifs (random vs. block) were prepared to study the effect of monomer arrangement throughout the polymer chain. The second goal involved functionalization of the polymer backbone post-polymerization via Click chemistry. The ease and utility of the Huisgen 1,3-dipolar cycloaddition reaction was exploited to attach several different pendant groups to a parent PT derivative. Additionally, the employment of post-polymerization modification facilitated purification of the different functionalized polymers. The final goal of the thesis was investigation of the influence of pendant groups on the optical and electronic properties of the parent polymer for potential applications towards organic material based devices. In particular, DTE and TEMPO were the pendant groups of choice. DTE was attached to the PT backbone to investigate the influence of the ring closing reaction on the luminescent properties of the polymer, and TEMPO was attached to study the potential increase in charging/doping of the polymer backbone.   54 1.7 References  1. Sonystyle Canada Home Page. http://www.sonystyle.ca/commerce/servlet/ HomepageView?storeId=10001&langId=-1&catalogId=10001. XEL-1 OLED TV. http://www.sonystyle.ca/commerce/servlet/ProductDetailDisplay?storeId =10001&catalogId=10001&langId=-1&productId=1004843 (accessed Sept 14 2009). 2. Sony Homepage. http://www.sony.ca/view/press_494.htm#. Sony Corporation Press Release. http://www.sony.ca/view/homepage.htm (accessed Sept 14 2009). 3. Moore, G. E., Electronics 1965, 38, (8). 4. CNET Homepage. www.cnet.com. New Life for Moore's Law. http://news.cnet.com/New-life-for-Moores-Law/2009-1006_3-5672485.html 5. Cui, H. 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Commun. 2007, (17), 1730-1732.    62 CHAPTER 2 Synthesis of Random Co-Polythiophenes Using GRIM Polymerization and Functionalization Via Huisgen 1,3-dipolar Cycloaddition∗ 2.1 Introduction Regioregular polythiophenes (rr-PTs) demonstrate improved optoelectronic properties such as higher mobilities1-5 and conductivities6-11 as compared to their regioirregular counterparts. The structural regularity of the polymer backbone gives rise to a more coplanar arrangement of the individual thiophene rings which results in more extended conjugation and thus smaller band-gaps resulting from the increased pi-overlap along the chain.12 In 1992, McCullough et al. introduced a synthetic method that generates almost exclusively HT rr-poly(3-alkylthiophene) (P3AT).8,9 The key step in this method is the regiospecific generation of a 2-bromo-5-bromomagnesio-thiophene. Scheme 2-1 outlines the general synthesis of rr-P3AT, starting from 2-bromo-3-alkylthiophene (53a) which is selectively activated with lithium diisopropylamide (LDA) in the 5-position generating intermediate 54 (intermediate 55 is only produced in a 1-2% yield, as demonstrated by quenching studies).9 Addition of Ni(dppp)Cl2 catalyzes the polymerization in situ via a cross-coupling reaction and leads to the desired HT rr-P3AT (Step 2). The number average molecular weights (n) are typically 20000 – 40000 g mol-1 with polydispersities (PDI) of 1.4.  ∗  A version of this chapter will be submitted for publication. Kunz, T. K.; Stott, T. L.; Wolf, M. O., Functionalized Polythiophenes via “Click Chemistry”.  63 Scheme 2-1 S R X Y S R M Y S R X M S R S R n +Step 1 Step 2 53 54 55 a) X=H, Y=Br b) X=Y=Br 56  An alternative synthetic route to HT rr-P3AT was developed by Rieke et al. where 2,5-dibromo-3-alkylthiophenes (Scheme 2-1, 53b) are treated with the highly reactive “Rieke zinc” (Zn*), a high surface area zinc powder, to afford the two isomeric intermediates (54 and 55) in a ratio of 9:1.7,13 The polymerization reaction is performed in situ using Ni(dppe)Cl2 as the catalyst. It was observed in the Rieke method that while highly reactive, the Zn* does not form any of the bis(bromozincio)thiophene, eliminating the need to stoichiometrically lithiate and quench the thiophene as in the McCullough method; however, the highly reactive Zn* leads to metallation that is slightly less selective for isomer 54 and still requires cryogenic temperatures. The typical values of n for the Rieke method are observed in the range of 24000 - 34000 g mol-1 with a PDI of 1.4. Several other methods have also been developed to prepare HT rr-P3AT. For example, modified Stille and Suzuki-Miyaura reactions were used for the palladium catalyzed cross-coupling of stannane and boronate intermediates respectively (Scheme 2-2). In 1998, Iraqi et al. used 2-iodo-3-alkyl-5-(tri-n-butylstannyl)thiophene derivatives (57) to generate HT rr-P3AT with greater than 96% HT coupling.14 Also in 1998, Guillerez et al. used 3-octyl-2-iodo-5-boronatothiophene (58) to achieve rr-P3AT with 96-97% regioregularity.15 Both of these methods, however, require cryogenic temperatures to obtain the organometallic monomers which in turn require purification  64 prior to subsequent reactions and afford much lower number average molecular weights (~ 10000 - 16000 g mol-1). Scheme 2-2 S R IBu3Sn S R IB O O S R S R n Pd(PPh3)4 various solvents reflux, 16 h Pd(OAc)2 THF, EtOH, H2O  reflux, 16 h 5657 58 K2CO3   In 1999, a new method for preparing rr-P3ATs was developed whereby a Grignard reagent is generated in situ at room temperature or reflux and then addition of a nickel catalyst affords the rr-P3AT.16 This method (known as the Grignard Metathesis (GRIM) polymerization) offers one paramount advantage over other methods as it does without the highly reactive metals that are required to generate the regio-specific 2- bromo-5-bromomagnesio-3-alkylthiophene intermediate. This eliminates the need for cryogenic temperatures, thus making feasible kilogram scale reactions that still result in high molecular weight rr-P3AT. Starting from 2,5-dibromo-3-alkylthiophene (Scheme 2-1, 53a), addition of one equivalent of a Grignard reagent affords a mixture of the intermediates 54 and 55, with the desired isomer 54 formed in 75-85% percent yield. While the ratio of desired (54) to undesired (55) isomer is not as high as in the McCullough and Rieke methods, this ratio is obtained independent of the Grignard reagent used, the length of reaction time, or reaction temperature. It also still affords polymers with greater than 99% HT couplings and typical n  values of 20000 – 35000 g mol-1 with low PDI of 1.2-1.4.17 Incorporation of side chains onto the PT backbone was first used to improve polymer solubility, but was also observed to modify the electronic properties of the  65 polymer. The introduction of electron donating groups or electron withdrawing groups was observed to decrease or increase the bandgap respectively as observed through shifts in the absorption spectrum of the polymer.6,7,9,11,13 Additionally, shifts in the absorption of the polymer are related to the oxidation/reduction potentials of the polymer. These potentials determine how readily the polymer may be doped and the stability of doped polymer. This is important for applications in light-emitting devices,18-20 field effect transistors,21,22 and solar cells.23-25 Typical modifications to a polymer backbone via side-chain elaboration are installed by changes to the monomer species prior to polymerization. While the GRIM polymerization is compatible with a variety of side chain functionalities,26 obtaining narrow polydispersity materials is still labour intensive, generally requiring repeated Soxhlet extractions. Post-polymerization modification is an alternate method to prepare a series of related polymers bearing a variety of side chains. The work discussed herein demonstrates side chain elaboration through the incorporation of an azide functionality into the polymer backbone. The azide is reacted with a terminal acetylene via a CuI catalyzed Huisgen 1,3-dipolar cycloaddition 'Click' reaction, forming the stable triazole ring as shown in Scheme 2-3 below. Advantages of this reaction include its irreversibility and high yield.27 In addition, the acetylene (29) and azide (30) starting materials do not react with themselves and are known to be tolerant of many different functional groups.28  66 Scheme 2-3 N N N R2 N N N R1 R2 1,4-triazole + CuI N N N R1 R2 1,5-triazole major minor 29 30 31 32 H R1 +   In this chapter, the synthesis and characterization of a HT rr-P3AT using GRIM conditions and containing latent functionality within the backbone is reported. A parent copolymer is prepared which contains hexyl side chains to maintain solubility and azide groups to provide reactive sites for further functionalization post-polymerization. The feasibility of post-polymerization functionalization will be demonstrated with the generation of a several new functionalized copolythiophenes.   67 2.2 Experimental 2.2.1 General All reagents and solvents were used as received except where noted. Tetrahydrofuran (THF) was distilled from Na/benzophenone. Anhydrous dimethylformamide (DMF) was obtained from Aldrich. 1H NMR spectra were obtained in CDCl3 either on a Bruker AV- 400 Inverse, a Bruker AV- 400 Direct, or a Bruker AV- 300 spectrometer. Chemical shifts (δ) are reported in ppm, referenced to residual chloroform (CHCl3) (δ 7.27). Coupling constants (J) are reported in Hertz. Integration of 1H NMR spectra shows slight variations from batch to batch of similarly prepared GRIM polymers. Consistency between samples was maintained by preparing all subsequent samples from a single precursor polymer. ATR-IR spectra were recorded on a Thermo Scientific Nicolet 6700 FT-IR spectrometer as neat powders or oils. Electronic absorption spectra were obtained on a Varian Cary 5000 UV-vis spectrometer in HPLC grade CH2Cl2 and CHCl3. Fluorescence measurements were carried out on a PTI Quantamaster spectrometer in the same solvents used for UV-vis measurements. Molecular weight distribution curves of polymers were determined by size exclusion chromatography (SEC) was performed using a Waters SEC equipped with 3 µg-Styrgel columns against polystyrene standards.  Polymers were dissolved, filtered and eluted with THF at a flow rate of 1.0 mL/min and monitored with a UV-vis detector (Waters 2487). Data was acquired and analyzed using an IBM personal computer and custom-written software. Electrochemical measurements were conducted on a Autolab PGSTAT12 using a Pt disk working electrode, Pt mesh counter electrode, and a Ag wire reference electrode. These  68 measurements were made in CH2Cl2 passed through an alumina column. An internal reference (decamethylferrocene) was added to correct the measured potentials with respect to saturated calomel electrode (SCE). The 0.1 M [n-Bu4N]PF6 supporting electrolyte was purified by triple recrystallization from ethanol and dried at 90 ºC under vacuum for 3 days.  2.2.2 Procedures 2,5-Dibromo-3-hexylthiophene. (60) SBr Br  This compound was prepared via a modified literature procedure.29 A solution of 3-hexylthiophene (5.0 g, 30 mmol), and N-bromosuccinimide (NBS) (10.5 g, 59.5 mmol) was prepared in DMF (50 mL). The flask was covered with Al foil and heated to 40 ºC under N2 for 16 hours. The solution was poured into cold water (100 mL) and extracted with diethyl ether (5 × 25 mL). The organic layer was then washed with  water, decolourized with activated carbon, filtered, dried (Na2SO4) and filtered a second time. The solvent was removed under reduced pressure and purified by column chromatography through silica gel (hexanes) to yield a colourless oil. Yield: 8.76 g (90%). 1H NMR (400 MHz, CDCl3, δ):  6.79 (s, 1H), 2.52 (t, 2H), 1.56 (m, 2H), 1.32 (m, 6H), 0.92 (t, 3H).  69 3-(2′-Bromoethyl)thiophene. (62) S Br  This compound was prepared via modified literature procedures.30,31 2-(3′- thienyl)ethanol (2.0 mL, 18 mmol) and CBr4 (7.29 g, 21.7 mmol) were dissolved in CH2Cl2 (125 mL). The solution was cooled to 0 ºC and PPh3 (7.13 g, 27.2 mmol) was added in one portion. The solution became pale yellow in color, and the reaction was allowed to warm to room temperature and stirred overnight. The solution was filtered through a silica plug (× 2) using CH2Cl2 to remove the yellow colour and PPh3O. The solvent was removed under reduced pressure to yield the crude product, which was purified by column chromatography on silica gel (hexanes). Removal of the solvent gave 62 as a colourless oil. Yield: 3.44 g (99%). 1H NMR (300 MHz, CDCl3, δ): 7.34 (dd, 1H), 7.13 (m, 1H), 7.04 (dd, 1H),  3.62 (t, 2H), 3.62 (t, 2H).  2,5-Dibromo-3-(2′-bromoethyl)thiophene. (63) S Br Br Br  This compound was prepared via a modified literature procedure.32 Compound 62 (1.0 g, 5.2 mmol) was dissolved in DMF (25 mL), the solution was deaerated with N2 and cooled to 0 ºC. The round bottom flask was then covered with Al foil. A solution of NBS (2.04 g, 11.5 mmol) in N2 deaerated DMF (25 mL) was added, the resultant solution  70 heated to 40 °C and left overnight. The solution was removed from heat and poured into cold water (100 mL). The organics were extracted with diethylether (3 × 50 mL), washed with 1 M aqueous NaHCO3, dried (Na2SO4) and filtered. The solvent was removed under reduced pressure and was purified by column chromatography through silica gel (hexanes). Yield: 1.57 g (86%). 1H NMR (300 MHz, CDCl3, δ):  6.87 (s, 1H), 3.50 (t, 2H), 3.11 (t, 2H).  2,5-Dibromo-3-(2′-azidoethyl)thiophene (64) S N3 Br Br  Compound 63 (1.03 g, 2.98 mmol) and NaN3 (0.29 g, 4.5 mmol) were dissolved in N2 purged 1-propanol (25 mL). The solution was then heated to reflux overnight. The cooled solution (slightly yellow in color) was extracted with CHCl3, washed with water, dried (Na2SO4) and filtered. The product was isolated as an oil via column chromatography (silica, hexanes, Rf = 0.21) Yield: 0.73 g (88%). 1H NMR (400 MHz, CDCl3, δ): 6.85 (s, 1H), 3.46 (t, J = 7.0 Hz, 2H), 2.82 (t, J = 7.0 Hz, 2H). 13C NMR (100.5 MHz, CDCl3, δ): 138.2, 130.7, 111.0, 109.7, 50.3, 29.0. EI-MS (m/z): M+ 310. ATR-IR (ν, cm-1): 2956, 2867, 2086 (νN3), 1541, 1455, 1417, 1345, 1262, 1001, 825, 631, 475. UV-vis (CH2Cl2): λmax = 251 nm (ε, L mol-1 cm-1: 8.6×104). Anal. Calcd for C6H5Br2N3S (%): C, 23.17; H 1.62; N, 13.51. Found: C 23.28; H 1.78; N 13.23.   71 Poly-3-hexylthiophene-co-3-(2′-bromoethyl)thiophene (Poly-1). S S Br C6H13 x y n {x:y; 1:2}  To a round bottom flask containing 100 mL of dry THF, 2,5-dibromo-3-(2′- bromoethyl)thiophene (2.03 g, 5.83 mmol) and 2,5-dibromo-3-hexylthiophene (1.90 g, 5.83 mmol) were added. Methyl magnesium bromide (1.4 M in THF/toluene) (8.33 ml, 8.96 mmol) was added and the solution was heated to reflux for 3 hours during which time the color changed from colorless to orange. The solution was then cooled slightly and 2 mol% of Ni(dppp)Cl2 was added in one portion. The color changed rapidly to dark red with yellow fluorescence and the solution was heated to reflux overnight. The reaction mixture was then allowed to cool to room temperature and the dark purple polymer precipitated from vigorously stirred methanol. The solid was purified by sequential overnight Soxhlet extractions (24 h CH3OH, 24 h hexanes, 4 h CHCl3). Yield: 1.12 g (24%). 1H NMR (400 MHz, CDCl3, δ): 7.01 (s), 3.65 (s, -CH2CH2Br), 3.41 (s, - CH2CH2Br), 2.82 (s, -CH2CH2(CH2)3CH3), 1.72 (s, -CH2CH2(CH2)3CH3), 1.45–1.35 (m, -CH2CH2(CH2)3CH3), 0.93 (s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 2952, 2921, 2852, 1558, 1507, 1452, 1376, 1302, 1263, 1207, 1102, 1061, 821, 722, 610, 562. UV-vis (CHCl3) λmax: 442 nm. Fluorescence (CHCl3) λmax: 572 nm. SEC: w = 15000 g mol-1, n = 7000 g mol-1, PDI = 1.8.    72 Poly-3-hexylthiophene-co-3-(2′-azidoethyl)thiophene (Poly-2). S S N3 C6H13 x y n {x:y; 1:2}  Poly-1 (0.363 g, 0.69 mmol) was placed in a round bottom flask in N2 purged DMF (150 mL). Under positive N2 pressure, NaN3 (0.664 g, 10 mmol) was added in one portion and the reaction was heated to 120 °C and left overnight. The solution was filtered warm to remove any insoluble mass and cooled to room temperature prior to being precipitated from vigorously stirred methanol (150 mL). The resulting dark purple solid was purified by re-precipitation from methanol twice more. Yield: 0.14 g (63%). 1H NMR (400 MHz, CDCl3, δ): 7.00 (s), 3.61 (s, -CH2CH2N3), 3.13 (s, -CH2CH2N3), 2.80 (s, -CH2CH2(CH2)3CH3), 1.70 (s, -CH2CH2(CH2)3CH3) 1.45-1.27 (m, -CH2CH2(CH2)3CH3) 0.93 (s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1) 2952, 2922, 2853, 2091(N3), 1560, 1509, 1454, 1376, 1259, 1087, 1016, 800, 723, 669, 447. UV-vis (CHCl3) λmax: 434 nm. Fluorescence (CHCl3) λmax: 572 nm. SEC: w = 12000 g mol-1, n = 5800 g mol-1, PDI = 2.1.   73 Methyl 1-(2-(2,5-dibromothiophen-3-yl)ethyl)-1H-1,2,3-triazole-4-carboxylate (65) BrSBr N N N O O  Compound 64 (0.31 g, 1.0 mmol), methylpropiolate (0.10 mL, 1.2 mmol), L- ascorbic acid (10 mol%) and CuSO4.5H2O (1 mol%) were each dissolved in a 1:1 mixture of t-BuOH:H2O (50 mL). Approximately 10 mL of CHCl3 was added after several hours to aid in dissolving 64. The reaction mixture was heated to reflux, and left overnight with vigorous stirring. The solution was cooled, and extracted (3 × 25 mL) with CHCl3 and washed (3 × 25 mL) with distilled water. It was then dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The 1,4-isomer (65) was purified by column chromatography (silica, CH2Cl2, Rf = 0.04). Yield 0.12 g (30%). 1H NMR (300 MHz, CDCl3, δ):  7.92 (s, 1H), 6.67 (s, 1H), 4.60 (t, J = 7.0, 2H), 3.96 (s, 3H), 3.20 (t, J = 7.0, 2H). 13C NMR (100.5 MHz, CDCl3): δ 161.0, 140.0, 136.7, 130.4, 127.6, 111.9, 110.6, 52.2, 49.8, 30.3. ESI-MS (m/z): [M + Na]+ 418. ATR-IR (ν, cm-1): 3137, 3099, 3076, 3037, 2951, 1723(C=O) 1546, 1524, 1465, 1452, 1434, 1422, 1370, 1317, 1216, 1112, 1051, 1036, 999, 970, 951, 925, 849, 810, 778, 698, 627, 578, 512, 471. UV- vis (CHCl3) λmax: 250 nm (ε, L mol-1 cm-1: 3.4 × 105), 256 nm (ε, L mol-1 cm-1: 3.7 × 105), 261 nm (ε, L mol-1 cm-1: 3.6 × 105). Anal. Calcd for C10H9Br2N3O2S (%): C, 30.40; H 2.30; N, 10.64. Found: C, 30.79; H, 2.69; N, 10.68.  74 BrSBr N N N O O  The 1,5-isomer (66) was isolated by column chromatography on silica gel (CH2Cl2, Rf = 0.13). Yield: 0.017 g (4.2%). 1H NMR (400 MHz, CDCl3): δ 8.12 (s, 1H), 6.74 (s, 1H), 4.92 (t, J = 7.2 Hz, 2H), 3.93 (s, 3H), 3.16 (t, J = 7.2 Hz, 2H). ESI-MS (m/z): [M + Na]+  418.  Poly-3-hexylthiophene-co-3-(2-(methyl-1H-1,2,3-triazole-4-carboxylate)ethyl)thiophene (Poly-3a) S S N N N C6H13 x y n O O {x:y; 1:2}  Poly-2 (27 mg, 0.085 mmol) and methylpropiolate (8.5 mg, 0.102 mmol) were dissolved in DMF (25 mL). The solution turned orange and was deaerated with N2 for ~ 15 min. L-ascorbic acid (10 mol%) and CuSO4.5H2O (1 mol%) were each added in one portion and the reaction mixture was slightly heated to dissolve the polymer. The reaction was left overnight under vigorous stirring. The solution was cooled, and the polymer precipitated from methanol, isolated with vacuum filtration and washed via Soxhlet extraction (24 h CH3OH, 24 h hexanes, 4 h CHCl3). Yield: 0.017 g (53%). 1H NMR (400  75 MHz, CDCl3, δ) 8.00 (m), 6.94-7.00 (m), 4.75 (s, -CH2CH2N3), 3.92 (s, -OCH3), 3.49 (s, - CH2CH2N3), 2.80 (s, -CH2CH2(CH2)3CH3), 1.71 (s, -CH2CH2(CH2)3CH3), 1.44-1.26 (m, - CH2CH2(CH2)3CH3), 0.92 (s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 2953, 2919, 2850, 1724, 1542, 1434, 1367, 1226, 1203, 1102, 1082, 1044, 1026, 807, 774, 720, 697, 665, 504. UV-vis (CHCl3) λmax: 439 nm. Fluorescence (CHCl3) λmax: 571 nm. SEC: w = 11000 g mol-1, n = 6300 g mol-1, PDI = 1.7.  Poly-3-hexylthiophene-co-3-(2-(1H-1,2,3-triazole-4-ferrocene)ethyl)thiophene (Poly-3b) S S N N N C6H13 x y n {x:y; 1:2} Fe  Poly-2 (0.0364 g, 0.115 mmol) and ethynylferrocene (0.0241 g, 0.115 mmol) were dissolved in DMF (15 mL). The solution turned orange and was deaerated with N2 for ~ 15 min. L-ascorbic acid (10 mol %) and CuSO4.5H2O (1 mol%) were each added in one portion and the reaction mixture was slightly heated to assist in dissolving the polymer. The reaction was left overnight with vigorous stirring. The solution was then cooled, and the polymer precipitated from methanol, isolated with vacuum filtration and washed via sequential Soxhlet extraction (24 h CH3OH, 24 h hexanes, 4 h CHCl3). Yield: 0.024 g (62%). 1H NMR (400 MHz, CDCl3, δ): 7.00-6.92 (m), 4.68 (s), 4.27 (s), 4.02 (s) 3.47 (s), 2.80 (s), 1.71 (s), 1.44-1.27 (m), 0.92 (s). ATR-IR (ν, cm-1): 2959, 2917, 2849,  76 1462, 1377, 1259, 1086, 1013, 876, 841, 794, 729, 700, 557, 504. UV-vis (CHCl3) λmax: 439 nm. Fluorescence (CHCl3) λmax: 571 nm. SEC: w = 15000 g mol-1, n = 7700 g mol-1, PDI = 2.0.  Poly-3-hexylthiophene-co-3-(2-(1H-1,2,3-triazole-4-amino)ethyl)thiophene (Poly-3c) S S N N N C6H13 x y n {x:y; 1:2} NH2  Poly-2 (0.029 g, 0.091 mmol) and 3-aminopropyne (0.01 mL, 0.2 mmol) were dissolved in 15 mL DMF. The solution turned cloudy orange and was deaerated with N2 for ~ 15 min. L-ascorbic acid (10 mol%) and CuSO4.5H2O (1 mol%) were each added in one portion and the reaction mixture heated slightly to help dissolve the polymer. The reaction was left overnight under vigorous stirring. The solution was cooled, the polymer precipitated from vigorously stirred methanol/water (5:1). The solid was isolated with vacuum filtration and washed via sequential Soxhlet extraction (24 h CH3OH, 24 h hexanes, 4 h CHCl3). Yield: 0.024 g (71%). ATR-IR (ν, cm-1): 3270, 2922, 2852, 1602, 1433, 1375, 1332, 1046, 822, 722, 609, 443.    77 2.3 Results and Discussion 2.3.1 Monomer Synthesis and Spectroscopy Multifunctional polymers for materials applications require careful design. High molecular weight polymers generally require solubilizing groups to maintain processibility. Desired functionality is, in general, afforded through the modification of side chains along the polymer backbone. The synthesis of a multifunctional GRIM polymer was carried out by copolymerization of two different monomers (Scheme 2-4). Poly-3-hexylthiophene (P3HT), is known to remain soluble at high molecular weights,33 and therefore, 2,5-dibromo-3-hexylthiophene (60) was selected as one of the monomers. In order to incorporate the necessary latent functionality on the polymer backbone for post-polymerization functionalization, 2,5-dibromo-3-(2-bromoethyl)thiophene (63) was selected as the second monomer. An analogous strategy has been previously used by McCullough et al. using 3-(6-bromohexyl)thiophene to make a variety of functional PT derivatives.34 Scheme 2-4 S OH S Br CBr4 PPh3 CH2Cl2 S Br Br Br NBS DMF SBr BrS NBS DMF 40 oC S N3 Br Br NaN3 1-propanol reflux, 16 h 59 0 oC r.t0 oC 40 oC0 oC 60 61 62 63 64 16 h 16 h 16 h    78 Monomer 60 was synthesized via a modified literature procedure.29 The bromination of 3-hexylthiophene was performed using two equivalents of NBS in dry THF. The solution was left stirring overnight at 40 °C. The small amount of mono- brominated thiophene present was removed via column chromatography to obtain a near quantitative yield of the desired dibromo species 60. Monomer 63 was synthesized via a two step procedure, adapted from literature.30- 32  The bromination of 2-(3-thienyl)ethanol was first carried out using phosphonium bromide generated in situ from carbon tetrabromide and tri-phenylphosphine. The phosphine oxide generated as a side product during this reaction made isolation of 62 by column chromatography difficult due to the insolubility of the oxide in hexanes, clogging the silica column used for purification. To solve the aforementioned problem, it was necessary to run the methylene chloride (CH2Cl2) solution containing impure product twice through a short silica plug using CH2Cl2 as the eluent. Once the oxide had been removed, the remaining material could be eluted with hexanes on a silica column to isolate the desired product as confirmed by 1H NMR spectroscopy. In the second step, thiophene 62 was brominated in the α-positions with two equivalents of NBS following the same procedure as for the 3-hexylthiophene derivative. The identity of the desired product, 63, was confirmed by comparison to the 1H NMR spectrum of 63 from the literature.32  In addition to the two monomers, 60 and 63, synthesized for the co- polymerization reaction, 64 was prepared as a model to allow comparison with the appropriate polymers. Compound 64 was prepared by heating 63 to reflux overnight with  79 sodium azide (NaN3) in 1-propanol, and isolated by column chromatography as a pale yellow oil. The 1H NMR spectrum of 64 clearly shows the shift in resonance for the two methylene groups of the ethyl chain upon conversion of the bromide to the azide group. The two triplets at δ 3.11 and 3.50 assigned to the α and β methylene groups of the - CH2CH2Br, shift to δ 2.82 and 3.46 respectively. Thiophene 64 was further characterized by mass spectrometry, UV-vis and infrared spectroscopy and elemental analysis. The infrared spectrum was particularly useful for characterization due to the presence of the strong azide stretching band located at 2086 cm-1. 2.3.2 Polymer Synthesis and Spectroscopy Regioregular HT poly-3-hexylthiophene-co-3-(2′-bromoethyl)thiophene (Poly-1) was prepared by copolymerization of thiophenes 60 and 63 using the GRIM procedure (Scheme 2-5). Monomers 60 and 63 were dissolved in THF in a 1:1 molar ratio, and an equal molar amount of methyl magnesium bromide was added dropwise. This selectively generated the Grignard reagent at the 5-position of each monomer. The solution was then stirred at reflux for 3 hours, during which time the colourless solution became dark red/orange. The solution was cooled to room temperature and 2 mol% Ni(dppp)Cl2 added to initiate the polymerization. The polymerization proceeds via Kumada coupling where the aryl Grignard reagents selectively react with the available aryl halides. The resulting polymer was purified via sequential Soxhlet extractions to yield a purple solid. An overnight methanol extraction was used to remove starting materials and initiator, followed by an overnight hexanes extraction to remove shorter chains and oligomers, and  80 finally, a chloroform extraction to isolate the soluble polymer from any residual insoluble material.  Scheme 2-5 S S N3 C6H13 x y n {x:y; 1:2} S S Br C6H13 x y n {x:y; 1:2} SBr Br Br + SBr Br 1) MeMgBr / THF reflux, 3 h 2) 2 mol% Ni(dppp)Cl2 reflux, 16 h 60 63 Poly-1 Poly-2 reflux, 16 h NaN3 DMF   Regioregular HT poly-3-hexylthiophene-co-3-(2′-azidoethyl)thiophene (Poly-2) was prepared by dissolving Poly-1 in DMF, adding an excess of NaN3 to the solution and stirring overnight at 120 °C (Scheme 2-5). The following day the dark red-purple solution was filtered hot, to remove any insoluble species. It has been observed previously35-38 that elevated temperatures can decompose azides to highly reactive nitrenes. Nitrenes can then insert into single or double bonds, resulting in cross-linking between the polymer chains which may result in insoluble high molecular weight polymers. Purification of Poly-2 was performed via re-precipitation from vigorously stirred methanol. Here, there  81 did not appear to be any significant loss of product due to cross-linking as observed by the lack of insoluble material remaining in the filter funnel after purification. 1H NMR spectroscopy of Poly-1 and Poly-2, showed signals that were characteristically broadened39 compared to the peaks of the corresponding monomeric species. It was observed that polymerization results in several significant shifts in the proton resonances (Figure 2-1). The signals from the α and β methylene groups of the polymer hexyl side chain have shifted to δ 2.82 (α) and 1.72 (β) from δ 2.52 (α''') and 1.56 (β''') respectively, and correspond to chemical shifts observed in rr-P3HT.9 The two methylene groups of the polymer ethyl side chain (α' and β') also shifted to higher frequency (δ 3.65 (β') and 3.41(α') from δ 3.50 (β'') and 3.11 (α'')).  Each of the peaks observed in the 1H NMR spectrum of Poly-1 were integrated relative to the broad singlet at δ 0.93 (γ) corresponding to the -CH3 group of the hexyl chain. Comparing the area of this peak to the area of the β' methylene singlet of the ethyl group at δ 3.65, it was determined that the x:y ratio approximates 2:1. While the two monomers 60 and 63 were added to the reaction mixture in the same molar ratio, it is possible that 60 is more reactive, leading to a slightly higher amount being incorporated into the copolymer.  82 pBr.esp 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm) BrEtTBr2.esp Br2HT.esp SBr Br SBr Br BrS S Br x y n α α β β α' α' β' β' α'' α'' β'' β'' α''' α''' β''' β''' γ γ γ' γ' X  Figure 2-1. 1H NMR spectra of Poly-1 (black), 60 (red), and 63 (green). X = residual CHCl3 in the deuterated solvent.  There are several weak signals in the alkyl (~ δ 2.5) and aromatic (~ δ 6.5) regions of the 1H NMR spectrum of Poly-1. These signals are a result of imperfections in the regioregularity of the PT backbone, in particular, protons that are influenced by HH/TT couplings within the polymer backbone. This has been previously observed in related polymers.9,40 Integration of the two weak signals at δ 2.58 and 2.48 established that Poly-1 contains ~ 85% rr-HT couplings. Conversion of Poly-1 to Poly-2 resulted in the shifting of the singlets at δ 3.65 and 3.41 to δ 3.61 and 3.13 in the 1H NMR spectra respectively (Figure 2-2). These shifts are consistent with those observed in the 1H NMR spectrum of 64 where shielding  83 contributes to a shift of approximately δ 0.04 and 0.3 for the β and α protons of the ethyl chain, respectively. The signal that remains at δ 3.41 is assigned to incomplete conversion of the bromide groups. 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm) X X S S Br C6H13 x y n α αβ β α' α' S S N3 C6H13 x y n β' β'  Figure 2-2. 1H NMR spectra of Poly-1 (black) and Poly-2 (red). X = residual CHCl3 and H2O in the deuterated solvent.  The conversion of Poly-1 to Poly-2 was further confirmed with ATR-IR spectroscopy. As observed in Figure 2-3, the appearance of the strong stretching frequency located at 2091 cm-1 is indicative of the azide functional group. Unfortunately, there was no clear indication in the IR spectrum if residual bromide groups were present in Poly-2 since the stretching frequency of a C-Br bond is typically found in the fingerprint region in the range from ~ 300-500 cm-1 and there are several overlapping signals found in Poly-1 and Poly-2 in this region.41  84 3500 3000 2500 2000 1500 1000 500 60 70 80 90  % T Wavenumber (cm-1) νN3  Figure 2-3. ATR-IR spectra of Poly-1 (black) and Poly-2 (red).  Table 2-1 summarizes the absorption and emission data of Poly-1 and Poly-2 obtained with UV-vis and fluorescence spectroscopy. These values are observed to be similar to that of HT rr-P3HT in both solution and solid state. In regio-random P3HT, containing 50% HT couplings, the solution absorbance maximum is at 436 nm,9 due to reduced conjugation along the polymer backbone caused by the steric induced twisting of the polymer backbone. The solid state absorption of Poly-1 displays the expected red shift for samples of HT P3ATs due to self-orientation in the solid state.10 These optical studies further confirm the high degree of HT regioregularity along the backbones of both Poly-1 and Poly-2.  85 Table 2-1. Absorption and emission data comparisons for Poly-1 and Poly-2  Poly-1 Poly-2 McCullough9 rr-P3HT Rieke7 rr-P3HT Random9 P3HT Absorptiona λmax (nm) 442 440 442 456 436 Emissiona λmax (nm) 572 573 - 569 -  Absorptionb λmax (nm) 519 - 504 - 480 a CH2Cl2; bThin films on glass slides cast from CHCl3.  2.3.3 Monomer Click Reaction and Spectroscopy  Sharpless et al. showed that while CuI can be directly used in the Click reaction, preparation of the copper catalyst in situ by reduction of CuII salts is a better approach since CuII salts are typically less expensive and are often of higher purity than CuI salts.42 The CuI catalyzed reactions require a co-solvent, a molar equivalent of a nitrogen base, and lead to higher yields of undesired by-products. The catalyst chosen for the work discussed herein was CuSO4.5H2O which is reduced from CuII to CuI in situ using ascorbic acid. Initial investigations of the Click reaction catalyzed by CuI were carried out using the azide thiophene 64 (Scheme 2-6). Compound 64 was dissolved in a mixture of t- BuOH:H2O:CHCl3 (2.5:2.5:1). To this solution was added one molar equivalent of methylpropiolate, 1 mol% CuSO4.5H2O and 10 mol% L-ascorbic acid. The solution was allowed to react overnight at reflux. The following day the sample was purified via column chromatography yielding the 1,4- and 1,5-substituted products 65 and 66 in a 6.5:1 ratio. In the 1H NMR spectra (Figure 2-4) of 65 and 66, the triazole protons of the  86 two isomers appear at δ 7.92 and δ 8.12, respectively, similar to analogous resonances in related compounds.42,43 Scheme 2-6 BrSBr N N N O O BrSBr N N N BrSBr N3 O O + H O O 1 mol% CuSO4.5H2O 10 mol% L-ascorbic acid DMF 64 65 66     8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 Chemical Shift (ppm) X BrSBr N N N O O BrSBr N N N O O α α β β σ σ α' α' β' β' σ' σ'  Figure 2-4. 1H NMR spectra isomers 65 (black) and 66 (red). X = residual CHCl3 in the deuterated solvent.   87 To distinguish between the two possible isomers, a 1H NMR nuclear Overhauser effect (NOE) difference spectral analysis was carried out. With this analysis, one can determine through space 1H-1H proximity within a molecule. A particular proton is irradiated and by means of the through space NOE, a proton close in space will display enhanced signal intensity.44 When the triazole proton (δ 7.92) of compound 65 was irradiated, the resonance signal of the β methylene triplet at δ 4.60 geminal to the triazole ring increased in intensity (Figure 2-5). A slight increase in intensity of the ester -CH3 group at δ 3.96 was also observed. In compound 66, irradiation of the triazole proton at δ 8.12, led only to an increase in intensity for the -CH3 group of the ester confirming that the major product is indeed the 1,4-substituted isomer. 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 Chemical Shift (ppm) NOE17b.mrc X BrSBr N N N O O σ σ β β  Figure 2-5. 1H-1H NMR NOE difference spectrum (red) and 1H NMR spectrum (black) of 65. X = residual CHCl3 in the deuterated solvent.  88 2.3.4 Polymer Click Reactions and Spectroscopy We selected several different acetylenes to demonstrate functionalization of Poly- 2 via the Click reaction. Reaction of Poly-2 with methylpropiolate, ethynylferrocene, or 3-aminopropyne gave Poly-3a, -3b and -3c respectively using reaction conditions similar to those established for the molecular Click reaction to generate thiophene 65 (Scheme 2-7). Scheme 2-7 Fe Poly-2 H R 1 mol% CuSO4.5H2O 10 mol% L-ascorbic acid DMF Poly-3a, 3b, 3c R = O O NH2 a b c S S N N N C6H13 x y n {x:y; 1:2} R S S N3 C6H13 x y n {x:y; 1:2}   Poly-3c is insoluble in many common organic solvents such as CHCl3, CH2Cl2, and THF and was characterized only by ATR-IR spectroscopy, which clearly shows the disappearance of the azide stretching band at 2091 cm-1 and the appearance of a broad signal at 3270 cm-1, in the characteristic range of -NH2 functional groups.41 It is possible that the insolubility is due to strong hydrogen bonding between amino groups on neighbouring polymer sidechains. Poly-3a and -3b were found to be soluble in common organic solvents such as CH2Cl2 and THF and were characterized by 1H NMR and ATR- IR spectroscopy, as well as SEC.  The absorption and emission spectra of both Poly-3a  89 and -3b did not show significant changes from those of Poly-2. To confirm the reaction of the azide moiety, the 1H NMR spectrum of Poly-3a was compared to that of compound 64. Figure 2-6 displays the new resonances attributed to reaction of the azide with methylpropiolate. In particular, the two sets of methylene protons (α' and β') shift downfield and the methyl ester protons appear at δ 3.92. 8 7 6 5 4 3 2 1 0 Chemical Shift (ppm) S S N N N C6H13 x y n O O α'' β'' BrSBr N N N O O α β X β α α''β''  Figure 2-6. 1H NMR spectra of 65 (black) and Poly-3a (red).  The relative purity of Poly-3a and -3b was confirmed by the lack of signals due to starting material in the 1H NMR and ATR-IR spectra. In the 1H NMR spectra, the signals due to the acetylene proton for the ester and ferrocenyl starting materials at δ 2.90 and δ 2.75 respectively were not observed. As well, the ATR-IR spectra of both Poly-3a and - 3b were free of the characteristic acetylene stretching frequencies at ~ 3300 (ν≡C-H), and ~ 2150 (νC≡C) cm-1. ATR-IR spectroscopy also confirmed that the reaction had gone to completion as the azide stretching frequency at 2091 cm-1 disappeared.  90 It is of interest to substitute PTs with groups such as metal complexes having redox and optical properties that can be coupled to the polymer. The metal may have the capacity to influence the properties of the pi-conjugated polymer which can potentially give rise to new and enhanced properties.45 The ferrocenyl substituted PT, Poly-3b, was prepared as an example, showing that the Click methodology is a useful route to metal functionalized PTs. Ferrocene functionalized PTs, prepared both via electrochemical and chemical coupling routes have been previously studied.46,47 Cyclic voltammetry of Poly-3b was carried out in dry CH2Cl2 containing 0.1 M [n-Bu4N]PF6 as the supporting electrolyte. Scans were collected from +0.2 to +1.2 V vs. SCE on a Pt working electrode with a Pt-wire mesh counter electrode (Figure 2-7). The lower potential redox wave at Ered = 0.59 V is attributed to the ferrocenyl group based on CV studies of ethynylferrocene which shows a reversible redox wave at Ered = 0.66 V. The broad oxidation waves at higher potential are attributed to redox processes on the polymer backbone.48  91 0.2 0.4 0.6 0.8 1.0 1.2 -0.2 -0.1 0.0 0.1 0.2 0.3 Cu rr e n t (µ A) Potential (V) vs SCE  Figure 2-7. Cyclic voltammogram of Poly-3b on a Pt button electrode in dry CH2Cl2 containing 0.1 M [n-Bu4N]PF6. Scanned from +0.2 to +1.2 V vs. SCE, scan rate = 100 mVs-1.   92 2.4 Conclusions GRIM polymerization was successfully used to prepare a rr-PT which contained both solubilizing groups and latent functionality. The copolymer was determined to have an 85% HT content by 1H NMR, and the extent of regioregularity was further validated by the significant red shift observed in the electronic absorption spectrum. It was demonstrated that latent functionality built into the original polymer facilitated synthetic manipulation of the side chains post-polymerization. Several functionalized PTs were prepared using the Sharpless Click reaction.  93 2.5  References 1. Assadi, A.; Svensson, C.; Willander, M.; Inganäs, O., Appl. Phys. Lett. 1988, 53, (3), 195-197. 2. Bao, Z. N.; Lovinger, A. J., Chem. Mater. 1999, 11, (9), 2607-2612. 3. Chang, J. F. et al., Chem. Mater. 2004, 16, (23), 4772-4776. 4. Sirringhaus, H. et al., Nature 1999, 401, (6754), 685-688. 5. Sirringhaus, H.; Tessler, N.; Friend, R. H., Science 1998, 280, (5370), 1741-1744. 6. Chen, T. A.; Rieke, R. D., Synth. Met. 1993, 60, (2), 175-177. 7. Chen, T. A.; Wu, X. M.; Rieke, R. D., J. Am. Chem. Soc. 1995, 117, (1), 233-244. 8. McCullough, R. D.; Lowe, R. D., J. Chem. Soc., Chem. Commun. 1992, (1), 70- 72. 9. McCullough, R. D.; Lowe, R. D.; Jayaraman, M.; Anderson, D. L., J. Org. Chem. 1993, 58, (4), 904-912. 10. McCullough, R. 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In Handbook of Conducting Polymers, Skotheim, T. A., Elsenbaumer, R. L., Reynolds, J. R., Eds. Marcel Dekker: New York, 1986; pp 823-845. 20. Perepichka, I. F.; Perepichka, D. F.; Meng, H., Thiophene-based Materials for Electroluminescent Applications. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 1, pp 695-756. 21. Facchetti, A., Electroactive Oligothiophenes and Polythiophenes for Organic Field Effect Transistors. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 1, pp 595-646. 22. McCulloch, I.; Heeney, M., Thienothiophene Copolymers in Field Effect Transistors. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. 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Rev. 1992, 92, (4), 711-738.     97 CHAPTER 3 Synthesis and Characterization of Dithienylethene Modified Oligo- and Polythiophenes∗ 3.1 Introduction Polythiophenes (PTs) are an important class of CPs. They form some of the most environmentally and thermally stable materials for potential applications in: OLEDs,1-3 sensors,4,5 batteries,6,7 OPVs,8-10 and transistors.11,12 The clear relationship between structure and function dictates that a directed synthesis will lead to a better defined structure and therefore more predictable properties. The GRIM polymerization is an ideal method because it affords high HT regioregularity within a polymer backbone,13,14 and contributes to improved chemical properties such as a smaller bandgap and higher conductivities.15-17 Introduction of additional functionality to the polymer backbone leads to further tuning and modification of the polymer properties compared to those of unsubstituted PT.18-20 Modification of polymer properties via functional side groups that can have properties such as refractive index, conductivity, absorption or luminescence altered in- situ are appealing for applications in electronic and electrochemical devices.21 Of particular interest are a family of compounds that possess a hexatriene moiety that can be photochemically and reversibly transformed between two isomers; a phenomenon known as photochromism. Here, absorption of electromagnetic radiation of a specific wavelength induces a reversible chemical transformation between the two isomers A and  ∗  A version of this chapter has been published. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Reversible Amplifed Fluorescence Quenching of Dithienylethene Functionalized Polythiophene. Adv. Mater. 2008, 20, (10), 1998-2002.  98 B, with each isomer having unique absorption spectra as well as distinct structural and chemical properties.22 One of the most promising examples of the hexatriene backbones is found in 1,2- dithienylethenes (DTEs), a class of light-activated molecular switches. DTEs can be interchanged between two thermally stable isomers when irradiated with UV and visible light, inducing the ring-closing and ring-opening reactions respectively (Figure 3-1).21,23 In addition to thermal irreversibility, the ring-opening/ring-closing cycles are highly fatigue resistant, capable of more than 10,000 repetitions without losing photochromic performance.21,23 These properties are indispensible for application of DTE molecules in optoelectronic devices such as memories24-26 and switches.27-31 300 400 500 600 700 800 Ab so rb a n ce  (a. u ) Wavelength (nm) S S F F F F F F O S S F F F F F F O UV Visible 37o 37c  Figure 3-1. Typical absorption spectra of the ring-open (black) and ring-closed (red) isomers of substituted DTE.   99 In the following discussion, a rr-P3AT prepared via GRIM synthetic conditions is functionalized with acetylene modified DTE using the Click reaction. The coupling of the photo-induced cyclization of DTE to the enhanced electronic properties of a regioregular polymer may have potential for developing optically triggered organic materials. The syntheses of several DTE functionalized rr-P3AT analogs are reported. Typical spectroscopic and chromatographic characterizations of each analog are presented and structural differences are compared for their potential influence on the properties of the polymer backbone.  100 3.2 Experimental 3.2.1 General All reagents and solvents including deuterated solvents for NMR analysis (Cambridge Isotope Laboratories) were used as received unless otherwise noted. Tetrahydrofuran (THF) was distilled from Na/benzophenone. Anhydrous N,N- dimethylformamide (DMF) was obtained from Aldrich (sure-seal). Column chromatography was performed using silica gel 60 (230-400 mesh) from Silicycle Inc. Compound 37 was prepared as described in literature32 by Dr. Jeremy Finden in Prof. Branda’s group at Simon Fraser University. O S S F F FF F F 37 1H NMR and 13C NMR spectra were obtained on a Bruker AV-600, Varian Inova 500, Bruker AV-400 Inverse, Bruker AV-400 Direct, or Bruker AV-300 spectrometer. 19F NMR spectra were obtained on a Bruker AV-300 spectrometer. Chemical shifts (δ) are reported in parts per million (ppm), referenced to residual chloroform (CHCl3). Coupling constants (J) are reported in Hertz (Hz). Integration of 1H NMR spectra shows slight variations from batch to batch of similarly prepared GRIM polymers. Consistency between samples was maintained by preparing all subsequent samples from a single precursor polymer. Photostationary states (PSS) are reported as percent ring-closed isomer to ring-open as determined by integration of DTE resonance peaks in 1H NMR  101 spectra. ATR-IR spectra were recorded on either a Thermo Scientific Nicolet 6700 FT-IR spectrometer as neat oils or powders. Molecular weight distribution curves of polymers were determined by size exclusion chromatography (SEC) was performed using a Waters SEC equipped with 3 µg-Styrgel columns against polystyrene standards.  Polymers were dissolved, filtered and eluted with THF at a flow rate of 1.0 mL/min and monitored with a UV-vis detector (Waters 2487). Data was acquired and analyzed using an IBM personal computer and custom-written software. All of the reactions and spectroscopic analyses involving the DTE species were performed in darkened rooms or nearly dark conditions to prevent unwanted ring-closing/opening events.  3.2.2 Procedures Synthesis of 3-(2'-azidoethyl)thiophene (67) S N3  This compound was prepared via modifications to the literature procedure.33 To a vigorously stirred solution of 3-(2'-bromoethyl)thiophene (2.65 g, 13.9 mmol) in ethanol (50 mL), sodium azide (1.84 g, 28.3 mmol) was added and the resulting mixture was heated to and maintained at 85 °C overnight. The reaction was removed from heat, allowed to cool to room temperature, gravity filtered and concentrated under reduced pressure. The resulting oil was purified via column chromatography (silica, hexanes) to yield a colourless oil. Yield: 0.63 g (30%). 1H NMR (300 MHz, CDCl3, δ): 7.31 (m, 1H), 7.07 (m, 1H), 6.98 (dd, 1H), 3.52 (t, 2H), 2.95 (t, 2H).  102 Synthesis of Compound 68 S N O S S F F FF F F N N   A vigorously stirred solution of 67 (0.10 g, 0.65 mmol) and DTE-37 (0.206 g, 0.359 mmol) in t-C4H9OH (15 mL) was treated with a solution of L-ascorbic acid (0.102 g, 0.065 mmol) and CuSO4·5H2O (2 mg, 0.006 mmol) in a minimal amount of water (2 mL). After stirring at room temperature for one hour, the organic fraction was extracted with chloroform (3 × 25 mL). The combined organic fractions were washed with distilled water (3 × 25 mL), dried over MgSO4, filtered and evaporated under reduced pressure. Compound 68 was purified by column chromatography (silica, CH2Cl2/hexanes 3:1) and recrystallized from ethanol. Yield: 0.10 g (38%). mp = 158ºC. 1H NMR (400 MHz, CDCl3, δ): 7.55 (d, J  = 7.6 Hz, 2H), 7.47 (d, J  = 8.5 Hz, 2H), 7.39 (m, 3H), 7.31 (m, 4H) 7.16 (s, 1H), 6.97 (d, J = 8.7 Hz, 2H), 6.88 (m, 1H), 6.83 (d, J = 4.9 Hz, 1H), 5.23 (s, 2H), 4.60 (t, J = 7.0 Hz, 2H), 3.26 (t, J = 7.0 Hz, 2H), 1.97 (s, 3H), 1.96 (s, 3H). 13C NMR (75.5 MHz, CDCl3, δ): 158.0, 143.7, 142.2, 142.0, 141.3, 140.5, 137.0 133.3, 129.0, 127.9, 127.6, 127.0, 126.7, 126.4, 125.8, 125.7, 125.6, 122.9, 122.4, 122.3, 121.4, 115.3, 62.1, 51.1, 31.1, 14.5, 14.4 (27 of 36 carbons found). HR-MS (ESI) calcd for C36H27N3OF6NaS3 [M + Na]+ : 750.1118, found 750.1129. ATR-IR (ν, cm-1): 3040, 2928,  103 2872, 1606, 1557, 1538, 1510, 1506, 1464, 1339, 1269, 1241, 1214, 1185, 1138, 1112, 1052, 1035, 1011, 985, 899, 889, 857, 820, 803, 782, 750, 690, 669, 646, 555, 532, 505. UV-vis (C6H6) λmax : (open) 293 nm (ε, L mol-1 cm-1: 3.3×104); (closed) 276, 313, 590 nm (ε, L mol-1 cm-1: 1.4 × 104).  PSS: 95%.  Synthesis of Poly-4 S S N N N O C6H13 S S F F FF F F x y n {x:y; 1:2}  Poly-232 (0.0296 g, 0.061 mmol) and DTE-37 (0.0619 mg, 0.108 mmol) were dissolved in CHCl3 (20 mL) resulting in an orange solution. L-ascorbic acid (2 mg, 0.01 mmol) and CuSO4·5H2O (1 mg, 0.004 mmol) were dissolved in a 1:1 mixture of H2O and t-C4H9OH (10 mL) and added in one portion. The reaction mixture was heated to 90 ºC to dissolve the polymer and the vigorously stirred solution was left overnight. The solution was cooled and the purple polymer was precipitated from methanol (600 mL) and isolated with vacuum filtration. Poly-4 was then re-precipitated twice more to remove starting material and residual catalyst. Yield: 0.035 g (54%). 1H NMR (300 MHz, CDCl3, δ):  7.6–7.3 (m), 7.15 (s), 7.1–6.7 (m), 5.19 (br, s, -OCH2C=), 4.67 (br, s, -CH2CH2N), 3.42 (br, s, -CH2CH2N), 2.79 (br, s, -CH2CH2(CH2)3CH3), 1.93 (br, s, -CH3), 1.70 (br, s, - CH2CH2(CH2)3CH3), 1.5–1.1 (m, -CH2CH2(CH2)3CH3), 0.91 (br, s, -CH2CH2(CH2)3CH3).  104 ATR-IR (ν, cm-1): 2959, 2921, 2851, 1716, 1607, 1513, 1462, 1377, 1337, 1259, 1179, 1088, 1014, 886, 795, 688, 669. UV-vis (C6H6) λmax: (open) 290, 444 nm; (closed) 321, 347, 367, 385, 444, 592 nm. Fluorescence (C6H6) λmax: 574 nm. SEC: w = 16000 g mol- 1 , n = 8800 g mol-1, PDI = 1.9.  PSS: 96%.  Synthesis of sodium 4-hexyl-2-thienylboronate (69) S C6H13 B(OH)3Na  Synthesized with modifications from literature procedures.34,35 n-BuLi (18.0 mL, 1.6 M in hexanes, 29 mmol) was added dropwise to a solution of diisopropylamine (2.8 mL, 20 mmol) in dry THF (10 mL) at 0 °C and stirred for half an hour under a N2 atmosphere. A solution of 3-hexylthiophene (1.5 mL, 8.4 mmol) in dry THF (20 mL) was cooled to -78ºC and to this an aliquot of the Li[N(i-Pr)2] (14.3mL, 10.0 mmol) solution was added dropwise and the resulting solution was stirred for one hour before allowing the mixture to warm to room temperature over several hours. The solution was then re- cooled to -78 °C, trimethylborate (2.0 mL, 18 mmol) was slowly added, and the resulting mixture was again allowed to warm to room temperature overnight. The solution was hydrolyzed with 1 M HCl (20 mL), extracted with diethyl ether (3 × 25 mL), and washed with distilled water. The organic fraction was dried (MgSO4), filtered and sonicated (15 min) with solid NaOH. The resulting solid was filtered, re-acidified with 1 M  HCl (20 mL), extracted with diethyl ether (3 × 25 mL) and precipitated with solid NaOH pellets to yield 69 as a white solid. Yield: 0.94 g (45%), 1H NMR (300 MHz, D2O, δ): 6.93 (s, 1H), 6.90 (s, 1H), 2.57 (t, 2H), 1.58 (m, 2H), 1.28 (m, 6H), 0.83 (s, 3H).  105 Synthesis of Compound 70 S N3 S C6H13 S C6H13  2,5-dibromo-3-(2-azidoethyl)thiophene (7) (1.43 g, 4.60 mmol) was dissolved in dry, N2 sparged THF (40 mL) with Pd(PPh3)4 (0.160 g, 0.138 mmol).  A solution of 69 (2.37 g, 9.40 mmol) in saturated aqueous NaHCO3 solution was added and the reaction mixture turned milky white in colour. The solution was brought to reflux for two hours, cooled and poured over a saturated solution of NH4Cl. The organic compounds were extracted from the mixture with ethyl acetate (EtOAc) (3 × 25 mL), washed with distilled water, and dried (MgSO4). The solvent was removed via rotary vacuum evaporation. The remaining oil was purified by column chromatography (silica, 10% EtOAc in hexanes, Rf = 0.60) to give pure 70 as a yellow oil. Yield: 1.2 g (54%). 1H NMR (400 MHz, CDCl3, δ):  7.02 (d, J  = 1.4 Hz, 1H), 7.00 (s, 1H), 6.99 (d, J  = 1.0 Hz, 1H), 6.93 (s, 1H) 6.82 (s, 1H), 3.54 (t, J = 7.3 Hz, 2H), 3.06 (t, J = 7.5 Hz, 2H), 2.61 (m, 4H), 1.65 (m, 4H), 1.35 (s, 12H), 0.92 (s, 6H). 13C NMR (100.5 MHz, CDCl3, δ): 144.1, 143.8, 136.3, 136.0, 134.61, 134.57, 131.5, 127.5, 125.6, 125.7, 125.1, 120.3, 119.2, 51.2, 31.6, 30.43, 30.40, 30.3, 29.0, 28.9, 28.8, 22.6, 14.0 (23 of 26 carbons found). EI-MS (m/z): M+ 485. ATR- IR (ν, cm-1): 3096, 3048, 2953, 2923, 2853, 2091(νΝ3), 1547, 1529, 1459, 1416, 1377, 1346, 1295, 1247, 1212, 1140, 1113, 1040, 967, 907, 827, 728, 673, 640, 588, 563, 460. UV-vis (C6H6) λmax: 350 nm (ε, L mol-1 cm-1: 2.0 × 104). Fluorescence (C6H6) λmax: 423, 440 nm. Anal. Calcd for C26H35N3S3 (%): C, 64.29; H, 7.26; N, 8.65. Found: C, 64.07; H, 7.33; N, 8.68.  106 Synthesis of Compound 71 S N S C6H13 S C6H13 O S S F F FF F F N N  To a vigorously stirred solution of 70 (0.0305 g, 0.0628 mmol) and DTE-37 (0.0510 g, 0.0888 mmol) in dry THF (10 mL), a solution of L-ascorbic acid (0.007 g, 0.04 mmol) and CuSO4·5H2O (0.0012 g, 0.0048 mmol) in water (10 mL) was added. The solution was brought to reflux and left stirring for 48 hours. The reaction mixture was then cooled and extracted with diethyl ether (3 × 25 mL). The combined organic fractions were washed with distilled water (3 × 25 mL), dried (MgSO4), filtered and evaporated under reduced pressure. Compound 71 was purified by column chromatography (silica, 30% EtOAc in hexanes, Rf = 0.43) to yield a pale green sticky solid. Yield: 0.052 g (78%). 1H NMR (300 MHz, CDCl3, δ): 7.57-7.28 (m, 9H), 7.17 (s, 1H) 7.01-6.90  (m, 4H), 6.85 (d, J = 0.9Hz, 1H), 6.82 (s, 2H), 5.21 (s, 2H), 4.62 (t, J = 7.2 Hz, 2H), 3.37 (t, J = 7.2 Hz, 2H), 2.60 (m, 4H), 1.98 (s, 3H), 1.96 (s, 3H), 1.63 (m, 4H), 1.33 (s, 12H) 0.91 (t, J = 9.0 Hz, 6H). 13C NMR (100.5 MHz, CDCl3, δ): 169.22, 158.05, 144.26, 144.08, 143.84, 142.19, 142.02, 141.23, 140.38, 136.55, 136.05, 134.13, 133.44, 133.32, 131.95, 128.96, 127.85, 127.82, 126.89, 126.65, 125.85, 125.72, 125.58, 125.29, 122.93, 122.41,  107 121.37, 120.58, 119.47, 115.25, 62.08, 50.38, 31.64, 31.56, 30.46, 30.42, 30.33, 30.29, 30.16, 29.26, 28.98, 28.95, 22.63, 22.58, 14.51, 14.45, 14.08, 14.05 (48 of 56 carbons found).  EI-MS (m/z): M+ 1059. ATR-IR (ν, cm-1): 2953, 2925, 2854, 1607, 1553, 1513, 1464, 1437, 1378, 1336, 1269, 1246, 1180, 1136, 1111, 1052, 986, 950, 887, 821, 754, 689, 632, 562, 533, 506, 437. UV-vis (C6H6) λmax: (open) 298 nm (ε, L mol-1 cm-1: 3.4 × 104), 350 nm (ε, L mol-1 cm-1: 1.7 × 104); (closed) 350 nm (ε, L mol-1 cm-1: 2.4 × 104), 596 nm (ε, L mol-1 cm-1: 1.4 × 104). Fluorescence: λmax = 422, 440 nm.  PSS: 92%  Synthesis of Poly-5 S S Br C6H13 x y n {x:y; 2:3}  To a round bottom flask containing 100 mL of dry THF, 2,5-dibromo-3-(2′- bromoethyl)thiophene (2.66 g, 7.62 mmol) and 2,5-dibromo-3-hexylthiophene (2.51 g, 7.70 mmol) were added.  Methyl magnesium bromide (1.4 M in THF/toluene) (11.0 mL, 15.4 mmol) was added and the solution was heated to reflux for 2 hours during which time the color changed from colorless to orange. The solution was then cooled slightly and 0.5 mol% of Ni(dppp)Cl2 was added in one portion. The color changed rapidly to dark red with yellow fluorescence and the solution was heated to reflux overnight. The reaction mixture was allowed to cool to room temperature and the dark purple polymer precipitated from vigorously stirred methanol. The solid was purified by sequential overnight Soxhlet extractions with methanol and hexanes. Yield: 0.13 g (5.9%). 1H NMR  108 (300 MHz, CDCl3, δ): 7.00 (br, s), 3.63 (br, s, -CH2CH2Br), 3.39 (br, s, -CH2CH2Br), 2.80 (br, s, -CH2CH2(CH2)3CH3), 1.69 (br, s, -CH2CH2(CH2)3CH3), 1.5-1.1 (m, - CH2CH2(CH2)3CH3), 0.89 (br, s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 3054, 2956, 2922, 2852, 1557, 1506, 1449, 1376, 1303, 1260, 1208, 1087, 1015, 863, 796, 758, 723, 705, 662, 611, 593, 562, 483. UV-vis (C6H6) λmax: 411 nm. Fluorescence (C6H6) λmax: 565 nm. SEC: w = 4400 g mol-1, n = 2100 g mol-1, PDI = 2.8.  Synthesis of Poly-6 S S N3 C6H13 x y n {x:y; 2:3}  Following the same procedure used to synthesize Poly-2, Poly-5 (0.064 g, 0.073 mmol) was dissolved in 2:1 CHCl3:DMF (30 mL) and converted to Poly-6 which was obtained as a dark purple solid. Yield: 0.033 g (56%). 1H NMR (MHz, CDCl3, δ): 7.00 (br, s), 3.60 (br, s, -CH2CH2N), 3.11 (br, s, -CH2CH2N), 2.79 (br, s, - CH2CH2(CH2)3CH3), 1.71 (br, s, -CH2CH2(CH2)3CH3), 1.5–1.1 (m, -CH2CH2(CH2)3CH3), 0.91 (br, s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 2960, 2920, 2851, 2094 (νN3), 1655, 1521, 1437, 1415, 1376, 1346, 1258, 1168, 1082, 1013, 863, 793, 697, 661, 589, 546, 485. UV-vis (C6H6) λmax: 411 nm. Fluorescence (C6H6) λmax: 564 nm. SEC: w = 4700 g mol-1, n = 2600 g mol-1, PDI = 2.1.    109 Synthesis of the Poly-7 S S N N N O C6H13 S S F F FF F F x y n {x:y; 2:3}  Following the same procedure used to synthesize Poly-4, Poly-6 (0.011 g, 0.014 mmol) was dissolved in CHCl3 (25 mL) and converted to Poly-7 as a dark purple solid. Yield: 0.016 g (62%). 1H NMR (400 MHz, CDCl3, δ): 8.05 (br, s), 7.6–7.1 (m), 6.95 (br, s), 5.19 (br, s, -OCH2C=), 4.64 (br, s, -CH2CH2N), 3.42 (br, s, -CH2CH2N), 2.78 (br, s, - CH2CH2(CH2)3CH3), 1.94 (br, s, -CH2CH2(CH2)3CH3), 1.8–1.1 (m -CH2CH2(CH2)3CH3), 0.91 (br, s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 2962, 2907, 2852, 1515, 1444, 1413, 1337, 1258, 1081, 1011, 864, 791, 688, 661, 481. UV-vis (C6H6) λmax: (open) 289, 421 nm; (closed) 421, 600 nm .  Fluorescence (C6H6) λmax: 564 nm. SEC: w = 6300 g mol-1, n = 4300 g mol-1, PDI = 1.6.   110 Synthesis of Poly-9 S S Br C6H13 x y {x:y; 1:10}  A round bottom flask was charged with 2,5-dibromo-3-hexylthiophene (60) (1.55 g, 4.76 mmol) in dry THF (40 mL) and cooled to -78 °C under a N2 atmosphere. To this solution, methylmagnesium bromide (3.4 mL, 1.4 M in hexanes, 4.8 mmol) was added dropwise and then allowed to warm to room temperature before bringing the solution to reflux for 1.5 hours. The solution was cooled to allow addition of Ni(dppp)Cl2 (0.154 g, 0.286 mmol), immediately turning the solution red in colour. The resulting mixture was brought to reflux where yellow fluorescence was observed within 30 minutes via excitation with a hand held UV lamp. After three hours, the solution was cooled to room temperature, and a solution of 73 was added dropwise via syringe to the mixture. Intermediate 73 was prepared as follows.  A round bottom flask was charged with 2,5-dibromo-3-(2'-bromoethyl)thiophene (5) (0.166 g, 0.476 mmol) in dry THF (10 mL) and cooled to -78 °C under a N2 atmosphere. To this solution, methylmagnesium bromide (0.34 mL, 1.4 M in hexanes, 0.48 mmol) was added dropwise and then allowed to warm to room temperature before bringing the solution to reflux for two hours. Prior to addition of 73, a small aliquot of P3HT (Poly-8) was removed via syringe and precipitated from vigorously stirred methanol. The polymerization reaction was continued overnight, after which time the dark red solution was removed from heat and precipitated from vigorously stirred methanol. The resulting copolymer, Poly-9, was  111 worked up via sequential Soxhlet extractions (16 h CH3OH, 16 h hexanes, 4 h CHCl3). Yield: 0.11 g (12%). 1H NMR (400 MHz, CDCl3, δ):  6.99 (br, s), 3.57 (br, s, - CH2CH2Br), 3.48 (br, s, -CH2CH2Br), 2.81 (br, s, -CH2CH2(CH2)3CH3), 1.71 (br, s, - CH2CH2(CH2)3CH3), 1.36 (br, s, -CH2CH2(CH2)3CH3) 0.92 (br, s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 3054, 2953, 2921, 2852, 1633, 1563, 1510, 1455, 1376, 1263, 1187, 1171, 1105, 962, 887, 819, 577, 722, 667, 613, 592, 564, 536. UV-vis (C6H6) λmax: 427 nm. Fluorescence (C6H6) λmax: 567 nm. SEC: w = 15000 g mol-1, n = 6900 g mol-1, PDI = 2.0  Poly-8: S n  1H NMR (400 MHz, CDCl3, δ) 6.99 (br, s), 2.81 (br, s, -CH2CH2(CH2)3CH3), 1.71 (br, s, -CH2CH2(CH2)3CH3), 1.36 (br, s, -CH2CH2(CH2)3CH3) 0.92 (br, s, - CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 3054, 2954, 2919, 2850, 1633, 1563, 1510, 1454, 1376, 1260, 1094, 1017, 818, 800, 724, 662, 614, 597, 480. UV-vis (C6H6) λmax: 427 nm. Fluorescence (C6H6) λmax: 568 nm. SEC: w = 7300 g mol-1, n = 5600 g mol-1, PDI = 1.4  112 Synthesis of Poly-10 S S N3 C6H13 x y {x:y; 1:10}  Following the same procedure used to synthesize Poly-2, Poly-9 (0.082 g, 0.044 mmol) was converted to Poly-10 and obtained as a dark purple solid. Yield: 0.055 g (68%). 1H NMR (400 MHz, CDCl3, δ)  6.99 (br, s), 3.53 (br, s, -CH2CH2N), 3.12 (br, s, - CH2CH2N), 2.82 (br, s, CH2CH2(CH2)3CH3), 1.72 (br, s, -CH2CH2(CH2)3CH3), 1.45-1.36 (br, s, -CH2CH2(CH2)3CH3), 0.92 (br, s, -CH2CH2(CH2)3CH3). ATR-IR (ν, cm-1): 2955, 2921, 2852, 2097 (νN3), 1728, 1514, 1455, 1376, 1260, 1090, 1017, 863, 798, 723, 695, 482. UV-vis (C6H6) λmax: 428 nm. Fluorescence (C6H6) λmax: 568 nm. SEC: w = 5400 g mol-1, n = 4700 g mol-1, PDI = 1.2     113 Synthesis of Poly-11 S S N N N O C6H13 S S F FF FF F x y {x:y; 1:10}  Following the same procedure used to synthesize Poly-4, Poly-10 (0.029 g, 0.016 mmol) was converted to Poly-11 and obtained as a dark purple solid. Yield: 0.020 g (51%). 1H NMR (300 MHz, CDCl3, δ):  7.51 (br), 6.99 (br, s), 5.14 (br, -OCH2C=), 4.54 (br, -CH2CH2N) 3.49 (br, -CH2CH2N), 2.81 (br, s, -CH2CH2(CH2)3CH3), 1.92 (br, -CH3), 1.71 – 1.1 (br, -CH2CH2(CH2)3CH3),  0.91 (br, s, -CH2CH2(CH2)3CH3). 19F NMR (282 MHz, CDCl3, δ): -110.3, -132.2. ATR-IR (ν, cm-1): 2959, 2923, 2852, 1513, 1455, 1376, 1259, 1082, 1015, 863, 795, 724, 689, 468. UV-vis (C6H6) λmax: (open) 430 nm; (closed) 430, 600 nm. Fluorescence (C6H6) λmax: 567 nm. SEC: w = 6000 g mol-1, n = 4900 g mol-1, PDI = 1.3  114 3.3 Results and Discussion 3.3.1 Synthesis Initial investigations of the Click reaction with DTE-37 were carried out with a model compound (68) which was prepared to ensure that the reaction conditions were not incompatible with the DTE moiety. The model for a DTE functionalized random copolymer was synthesized via a Huisgen 1,3-dipolar cycloaddition Click reaction, from DTE-37 and 3-(2'-azidoethyl)thiophene (67) as shown in Scheme 3-1. The progress of the reaction between compound 67 and DTE-37 was monitored by thin layer chromatography (TLC), which showed that the reaction had reached completion within an hour while stirring at room temperature. The pure product, 68, was isolated by column chromatography, and further recrystallized from ethanol to yield a pale blue solid. Scheme 3-1 S N3 O S S F F FF F F S N R N N S Br NaN3 t-BuOH/H2O EtOH, 85 oC 16 h 20 mol% L-ascorbic acid 2 mol% CuSO4.5H2O rt, 1 h 37 67 68 R R = (DTE-37) H 62     115 The DTE modified PT Poly-4 was prepared using the same methodology as described for compound 68 (Scheme 3-2). The azide functionalized PT Poly-2 was dissolved in DMF containing an excess of DTE-37, based on the 2:1 ratio of hexyl to azide side chains within the polymer backbone determined from 1H NMR. The dark purple Poly-4 was precipitated directly into methanol and isolated by vacuum filtration. Poly-4 was purified by dissolving it in a minimal amount of CHCl3 and re-precipitation into methanol to remove catalyst and starting material. Scheme 3-2 S S N N N O C6H13 S S F F FF F F x y n S S N3 C6H13 x y n DTE-37 1 mol% CuSO4.5H2O 10 mol% L-ascorbic acid CHCl3 90 oC, 16 hr {x:y; 1:2} {x:y; 1:2} Poly-2 Poly-4   It was of interest to prepare several analogs of Poly-4 in order to investigate the effect of the conjugation length along the conjugated backbone. The well-defined structure of α-conjugated oligothiophenes can provide valuable information about the structure-property relationships, which are more difficult to deduce from the corresponding polydisperse polymer samples.  Studies have shown that oligomers beyond six to seven repeat units in length begin to display electrical, optical and physical  116 properties similar to an extended CP.36-38 For example, the pi-pi* optical transition of poly(3-hexylthiophene) has been observed in the region of 430-440 nm, comparable to a heptathiophene (440 nm) derivative.39 The similarity is related to the saturation of the effective conjugation length. In order to study a conjugated backbone of defined length with distinct properties, a terthiophene mimic of Poly-4 was prepared in two steps (Scheme 3-3). The azide 70 was prepared via Suzuki cross-coupling between compound 64 and two equivalents of sodium 4-hexyl-2-thienylboronate (69). Compound 64 was chosen as the central thiophene unit to incorporate the latent side chain functionality consistent with the structure of the backbone of Poly-4. Scheme 3-3 SBr N3 Br Pd(PPh3)4 S N3 S C6H13 S C6H13 S C6H13 B(OH)3Na NaHCO3(aq) THF S N S C6H13 S C6H13 O S S F F FF F F N N 6 mol% CuSO4.5H2O 50 mol%  L-ascorbic acid THF / H2O 90 oC, 48 h 71 DTE-37 + 2 reflux, 2 h 7064 69     117 Compound 70 is not regioregular; it contains both a HT and a TT coupling due to the asymmetry of the central thiophene unit. There are, however, no HH couplings that could cause steric disruptions between the alkyl chains and lead to undesirable twisting of the backbone. Click reactions between 70 and DTE-37 were initially performed using the same conditions described for the aforementioned model Click species, 68. Analysis by TLC of the crude mixture, after overnight reaction at reflux, showed large amounts of starting material and almost negligible amounts of product. Several trials were performed until favourable reaction conditions were determined. As shown in Scheme 3-3, it was found that 70 and DTE-37 required a much higher amount of the CuSO4·5H2O catalyst and L-ascorbic acid reducing agent, for unknown reasons. Using these conditions, pure 71 was obtained as a light green solid isolated by column chromatography. In addition to the oligomer analog 71, two polymeric variants of Poly-4 were prepared. The first variation, Poly-7, is most closely related in backbone structure to that of Poly-4 and varies only slightly in ratio between the two monomers but is significantly shorter in average chain length. The bromide precursor to Poly-7, Poly-5, was prepared under similar conditions to Poly-1, in order to obtain a comparable regiorandom backbone. To obtain a polymer with a shorter average chain length, Poly-5 was isolated from the hexanes fraction of the Soxhlet extraction during purification of the reaction mixture, and was reacted with NaN3 to yield Poly-6. Following the same synthetic route established for Poly-4, Poly-6 was converted to DTE containing Poly-7 (Scheme 3-4).   118 Scheme 3-4 S S N N N O C6H13 S S F F FF F F x y n S S N3 C6H13 x y n S S Br C6H13 x y n NaN3 DMF:CHCl3 {1:2} 90 oC, 16 h 1 mol% CuSO4.5H2O 10 mol% L-ascorbic acid CHCl3 90 oC, 16 h {x:y; 2:3} Poly-5 {x:y; 2:3} Poly-6 DTE-37 {x:y; 2:3} Poly-7   Secondly, the HT rr-block copolymer, Poly-9 was synthesized (Scheme 3-5). Studies have shown that GRIM polymerization proceeds in a quasi-living fashion via a chain growth mechanism.40-43 This allows for block copolymers to be prepared by the sequential addition of activated monomers. It has been shown that Ni(dppp)Cl2 behaves as an initiator for polymerization rather than as a catalyst. Thus the concentration of added Ni(dppp)Cl2 can be directly related to the number of initiated chains, and therefore can be used to predict the approximate molecular weight of the polymer.  119 Poly-9 was synthesized first with the generation of a pure P3HT block (Poly-8) using GRIM polymerization conditions (Scheme 3-5). Ni(dppp)Cl2 (6 mol%) was added in order to generate a polymer that would be shorter, on average, in length than Poly-4. The second block was formed with the addition of the activated monomer, 2-bromo-5- bromomagnesio-3-(2'-bromoethyl)thiophene (73) to allow further elaboration of the polymer to the DTE analog. Prior to the addition of 73, an aliquot of Poly-8 was removed and precipitated twice from methanol. Obtaining Poly-8 allowed for characterization of the initial block structure and was used to help confirm that the backbone was indeed composed of two different blocks. Scheme 3-5 S S Br C6H13 x y S C6H13 Br Br 2) 6 mol% Ni(dppp)Cl2 reflux, 2 h reflux, 3 h S C6H13 n SBrMg Br Br1) MeMgBr / THF reflux, 2 h THF {x:y; 1:10} 60 Poly-8 Poly-9 73 S C6H13 Br MgBr n MeOH workup 72   Poly-9 was first converted to an azide functionalized polymer (Poly-10) and then to the DTE functionalized species (Poly-11) following similar procedures used for each of the previously modified polymers (Scheme 3-6).  120   Scheme 3-6 S S N N N O C6H13 S S F FF FF F x y S S Br C6H13 x y Poly-11 1 mol% CuSO4.5H2O 10 mol% L-ascorbic acid DMF DTE-37 S S N3 C6H13 x y DMF NaN3 {x:y; 1:10} Poly-10 {x:y; 1:10} Poly-9 {x:y; 1:10}   3.3.2 NMR spectroscopy The 1H NMR spectrum (Figure 3-2) of compound 68 contained several signals assigned to the DTE moiety at δ 1.69, 1.70, and 4.98. These correspond to the two methyl groups (φ) located on the thiophene rings of the DTE, and the methylene spacer (χ) between the triazole ring and the ether tether of the DTE respectively. Two triplets, located at δ 2.57 and 3.75 are due to the α and β methylene protons of the ethylene  121 moiety adjacent to the thiophene ring. The aromatic region shows signals consistent with both the DTE group and thiophene ring. 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 Chemical Shift (ppm) α α β β φ φ χ χ X φ S N O S S F F FF F F N N  Figure 3-2. 1H NMR spectrum 68 dissolved in C6D6 (400 MHz). X = residual C6H6 in the deuterated solvent.  1H NMR spectroscopy was also used to monitor the extent of the ring-closing reaction as a function of irradiation time (Figure 3-3). The two resonances attributed to the methyl groups (φ) on the DTE core are observed at δ 1.70 and 1.69 in 68o. Upon irradiation of a C6D6 solution of 68 with 302 nm light, the singlets at δ 1.70 and 1.69 disappear and new singlets appear at δ 2.14 and 2.13 corresponding to ring-closed isomer (68c). When the ratio of 68o and 68c no longer changes the reaction is deemed to have reached the photostationary state (PSS). Here the PSS is comprised of 95% the ring- closed isomer. The PSS is defined as the point where equilibrium is reached between the competing ring-opening and ring-closing reactions. During the photo-induced ring-  122 closing reaction there is also a notable shift in the DTE methylene signal (χ) from δ 4.98 to 4.91. Irradiation of the ring-closed isomer with light greater than 530 nm resulted in the complete regeneration of the ring-open form without any indication of side products in the NMR spectrum. 3tk88c_1H_C6D6open.esp 5.0 4.5 4.0 3.5 3.0 2.5 2.0 Chemical Shift (ppm) 3tk88c_10min.esp 3tk88c_90min.esp 3tk88c_145min.esp a) b) c) d)  Figure 3-3. 1H NMR spectra of a C6D6 solution of 68o as a function of irradiation time (a) 0 min, (b) 10 min, (c) 90 min, (d) 145 min (400 MHz). Irradiation with UV-lamp at 302 nm.  In the 1H NMR spectrum of Poly-4, the absence of the terminal acetylene resonance at δ 2.54 confirmed that none of the DTE starting material was present in the product. Further evidence that the Click reaction proceeded are peaks in the 1H NMR spectrum that are consistent with those observed for the model compound 68. Two  123 diagnostic signals are located at δ 5.19 and 1.93 corresponding to the methylene spacer (χ) and the two methyl groups (φ) of the pendant DTE group (Figure 3-4). The characteristic broadening of these signals also indicates that the DTE is covalently bound to the polymer. The α and β methylene signals located at δ 4.67 and 3.43 have both shifted from lower frequency in agreement with the shift observed for the corresponding protons in the 1H NMR spectrum of 68. Integration of the aromatic region from δ 7.51 to 6.93 accounts for all of the expected thienyl and phenyl protons of the thiophene backbone and DTE pendant group. Several weak signals are found in the region from δ 2.0 to 5.0 which are attributed to HH/TT mis-couplings in the polymer backbone. The resonance located at δ 3.09 is attributed to residual –CH2CH2Br groups from incomplete conversion of Poly-1 to Poly-2.32  124 3tk45.esp 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm) S S N N N O C6H13 S S F F FF F F x y n α α β β χ χ φ φ X φ  Figure 3-4. 1H NMR spectrum of Poly-4 dissolved in C6D6 (300 MHz). X = residual CHCl3 present in the deuterated solvent.  The 1H NMR spectrum of 70 exhibits resonances between δ 7.02 to 6.82, with five distinctive signals; the two terminal thiophene rings each have two aryl protons, resulting in four doublets, while the internal thiophene ring has only one aryl proton resulting in a singlet. In the alkyl region of the 1H NMR spectrum, two triplets due to the α and β  methylene protons of the internal ethylene group are observed at δ 3.54 and 3.06 respectively. Four distinct resonance signals are observed for the two hexyl chains of the terminal thiophenes. Conversion of 70 to the DTE functionalized terthiophene 71 was verified via the 1H NMR spectrum of 71. The peaks at δ 5.21, 1.98, and 1.96 are the signals for the  125 methylene spacer (χ) and two methyl (φ) groups of the DTE group, respectively. As with 68, the β methylene protons shift significantly downfield from δ 3.54 to 4.62 upon formation of the triazole ring. 1H NMR confirmed the structure of Poly-5, -6 and -7 with spectra similar to that of the corresponding analogs Poly-1, -2 and -4. However, there were several significant structural differences indicated from the NMR spectra, between the backbone of Poly-5 to that of Poly-1. Integration of the signals at δ 2.80 and 3.63 in the 1H NMR spectrum of Poly-5, reveals a ratio of 3:2 for hexyl:bromoethyl side chains distributed along the polymer backbone. Furthermore, it was determined that the regioregularity of Poly-5 was lower than for Poly-1 with ~ 70% HT couplings for Poly-5 compared to 85% for Poly-1. This is contrary to the expected trend in regioregularity for GRIM polymerization. When the growing polymer chain experiences a HH or TT coupling this may reduce the activity of the growing chain end such that the steric bulk from the alkyl chain may inhibit further monomer addition. Thus, chains of higher regularity will preferentially react with the activated monomer to result in longer chains. The regioirregular chains are sterically compromised, resulting in shorter chains that end up being removed in the hexanes cycle of the Soxhlet extraction, from which Poly-5 was obtained. To verify the block structure of the resulting polymer, 1H NMR spectroscopic investigations of Poly-8 (essentially of the form rr-P3HT), were compared to the final block copolymer Poly-9. As seen in Figure 3-5, Poly-8 displays the expected resonance signals for a P3HT homopolymer.16,44 The broad singlets at δ 2.81, 1.71, 1.36 and 0.92 are due to the hexyl side chains, while the singlet at δ 6.99 is the resonance signal from the thienyl protons. Integration of the signals at δ 2.81 and 2.52 indicate that the polymer  126 backbone contains 82% HT couplings. In the 1H NMR spectrum of Poly-9, new signals are observed in the alkyl region from δ 3.0 to 3.6. The concentration of the activated monomer 73 was only 10 mol% that of 3-hexylthiophene, thus these new peaks are weak. Upon closer inspection of the spectrum, two signals were resolved at ~ δ 3.6 and 3.5, at similar chemical shifts to the signals of the α and β methylene protons on the ethyl chain of Poly-1. 3tk159_BpProof.esp 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm) X X S S Br C6H13 x y S C6H13 n α α , β β  Figure 3-5. 1H NMR spectra for Poly-8 (black) and Poly-9 (red) dissolved in CDCl3 (400 MHz). X = residual CHCl3 and water in the deuterated solvent.  The 1H NMR spectrum of Poly-10 also shows extremely weak signals in the methylene region from δ 3.0 to 3.6. This region can be magnified to show two signals that appear at the same relative chemical shift as those observed for the methylene protons of the ethyl chain in Poly-2 when the bromide is converted to an azide group. Upon reaction of Poly-10 with DTE-37, the new signals in the 1H NMR spectrum were very weak (Figure 3-6). At high magnification very weak signals at δ 5.14, 4.54 and  127 3.49 as well as tiny shoulder resonance signals at δ 7.51 and 1.91 were observed. In comparison to Poly-4, these match signals for the methylene protons at δ 5.19, 4.67, and 3.43, and phenyl and DTE-based methyl protons at δ 7.51 and 1.93, respectively. 3tk167_BpDTE_2.esp 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm) 3tk167_BpDTE_2.esp 7 6 5 4 3 2 Chemical Shift (ppm) 7. 50 5. 15 4. 54 3 . 49 1. 90 X S S N N N O C6H13 S S F FF FF F x y α α β β φ φ φ χ χ  Figure 3-6. 1H NMR spectrum of Poly-11 dissolved in CDCl3 (300 MHz). Inset shows the magnified baseline. X = residual CHCl3 in the deuterated solvent.  A 19F NMR spectrum of Poly-11 was also obtained to help confirm the presence of pendant fluorinated DTE. Two signals corresponding to DTE-37 were observed at δ - 110.3 and – 132.2.   128 3.3.3 Size Exclusion Chromatography SEC analyses were performed on each of the polymer species and the data is presented in Table 3-1. The first polymer prepared, Poly-4, was determined to have an average molecular weight of 16000 g mol-1 (vs. polystyrene in THF). From this value, the average number of thiophene rings in a chain could be calculated using the molecular weight of the average repeat unit. In the case of Poly-4, the average repeat unit consisted of three thiophene rings (1 DTE:2 hexyl; determined from 1H NMR) and the average polymer chain was calculated to contain 45 thiophene rings (15 repeat units).  Table 3-1. SEC comparative data for polymer series. Compound w (g mol-1) n (g mol-1) PDI Calculated # of Thiophene Units (monomersa) Poly-4 16000 8800 1.9 45(15) Poly-5 4400 2100 2.8 25(5) Poly-6 4700 2600 2.1 30(6) Poly-7 6300 4300 1.6 15(3) Poly-8 7300 5600 1.4 43 Poly-9 15000 6900 2.0 88(8) Poly-10 5400 4700 1.2 33(3) Poly-11 6000 4900 1.3 33(3) a Monomer: refers to the repeat unit determined from 1H NMR spectroscopy.  It was determined that the average molecular weights of Poly-5, -6, and -7 were approximately 3 times lower than that of Poly-4, with values in the range of ~ 5000 g mol-1 versus 16000 g mol-1. This was to be expected since Poly-5 had been isolated from the hexanes fraction of the Soxhlet extraction. The relatively high polydispersity of this  129 polymer series (Poly-5, -6, and -7) was unexpected such that fractionation should lead to a sample with more uniform molecular weights. Poly-8 was found to have an average molecular weight of 7300 g mol-1 (vs. polystyrene). Upon addition of the second monomer an increase in molecular weight was expected. The value obtained for Poly-9 was found to be approximately double that of the original hexyl block with an average molecular weight of 15000 g mol-1. This value does not agree with the results obtained from the 1H NMR spectrum. As well, the extremely low concentration of the second monomer made the dramatic increase in molecular weight inexplicable and deemed the results inconclusive. However, the SEC analyses of Poly-10 and Poly-11 yielded results more consistent with those of Poly-8, the synthetic procedures, and results from the 1H NMR spectra. It has been reported that extensive aggregation can occur in rr-P3AT that can lead to lead to significant errors in SEC.45 It has also been determined that molecular weights of PT can be overestimated by a factor of 10 when using polystyrene standards.46 The structure of the polymer backbone affects the behaviour of the polymers in solution, resulting in different amounts of coiling, spinning, and interaction of the polymer with the separation gel along the length of the column. Values of w have been reported at 130,000 g mol-1 after five repetitive analyses, until finally a value of 25,000 g mol-1 was obtained.47 Therefore, the inconsistencies discussed above are rationalized as SEC experimental errors.  130 3.4 Conclusions Several analogs of a DTE functionalized rr-PT were prepared. Variation of the GRIM polymerization methodology was successfully carried out to obtain both random and block copolymers while maintaining relatively high regioregularity; a minimum value of 70% HT couplings was obtained. A regioregular terthiophene was also prepared, via a modified Suzuki coupling reaction, to obtain an analog with a discrete conjugation path length.  The Click reaction provided a clean and efficient method for modification of each of the PT analogs resulting in DTE modified species, each displaying characteristic 1H NMR spectra.  The average polymer length and number of repeat units were determined from SEC data and the relative ratios of monomer species determined from 1H NMR spectroscopy.  131 3.5 References 1. Friend, R. H.; Greenham, N. C., Electroluminescence in Conjugated Polymers. In Handbook of Conducting Polymers, Skotheim, T. A., Elsenbaumer, R. L., Reynolds, J. R., Eds. Marcel Dekker: New York, 1986; pp 823-845. 2. Burroughes, J. H. et al., Nature 1990, 347, (6293), 539-541. 3. Perepichka, I. F.; Perepichka, D. F.; Meng, H., Thiophene-based Materials for Electroluminescent Applications. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 1, pp 695-756. 4. Ho, H.-A.; Leclerc, M., Chemical and Biological Sensors Based on Polythiophene. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 1, pp 813-832. 5. Thomas, S. W.; Joly, G. D.; Swager, T. M., Chem. Rev. 2007, 107, (4), 1339- 1386. 6. Suga, T.; Konishi, H.; Nishide, H., Chem. Commun. 2007, (17), 1730-1732. 7. Suga, T. et al., Adv. Mater. 2009, 21, (16), 1627-1630. 8. Dennler, G.; Scharber, M. C.; Brabec, C. J., Adv. Mater. 2009, 21, (13), 1323- 1338. 9. Xiao, S. Q.; Stuart, A. C.; Liu, S. B.; You, W., ACS App. Mater. & Inter. 2009, 1, (7), 1613-1621. 10. Kim, B. J.; Miyamoto, Y.; Ma, B. W.; Fréchet, J. M. J., Adv. Funct. Mater. 2009, 19, (14), 2273-2281.  132 11. Facchetti, A., Electroactive Oligothiophenes and Polythiophenes for Organic Field Effect Transistors. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 1, pp 595-646. 12. McCulloch, I.; Heeney, M., Thienothiophene Copolymers in Field Effect Transistors. In Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics, Perepichka, I. F., Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 1, pp 647-672. 13. Loewe, R. S.; Khersonsky, S. M.; McCullough, R. D., Adv. Mater. 1999, 11, (3), 250-253. 14. Loewe, R. S. et al., Macromolecules 2001, 34, (13), 4324-4333. 15. McCullough, R. D. et al., Synth. Met. 1995, 69, (1-3), 279-282. 16. McCullough, R. D.; Lowe, R. D., J. Chem. Soc., Chem. Commun. 1992, (1), 70- 72. 17. Chen, T. A.; Rieke, R. D., Synth. Met. 1993, 60, (2), 175-177. 18. Roncali, J., Chem. Rev. 1997, 97, (1), 173-205. 19. Somanathan, N.; Radhakrishnan, S., Int. J. Mod. Phys. B 2005, 19, (32), 4645- 4676. 20. Chan, H. S. O.; Ng, S. C., Prog. Polym. Sci. 1998, 23, (7), 1167-1231. 21. Irie, M., Photoswitchable Molecular Systems Based On Diarylethenes. In Molecular Switches, Feringa, B. L., Ed. Wiley-VCH GmbH: Weinheim, 2001; pp 37-61. 22. Bouas-Laurent, H.; Dürr, H., Pure Appl. Chem. 2001, 73, (4), 639-665.  133 23. Irie, M., Chem. Rev. 2000, 100, (5), 1685-1716. 24. Myles, A. J.; Branda, N. R., Adv. Funct. Mater. 2002, 12, (3), 167-173. 25. Myles, A. J.; Wigglesworth, T. J.; Branda, N. R., Adv. Mater. 2003, 15, (9), 745- 748. 26. Wigglesworth, T. J.; Branda, N. R., Chem. Mater. 2005, 17, 5473-5480. 27. Bertarelli, C. et al., Adv. Funct. Mater. 2004, 14, (4), 357-363. 28. Biteau, J. et al., Chem. Mater. 1998, 10, (7), 1945-1950. 29. Kronemeijer, A. J. et al., Adv. Mater. 2008, 20, (8), 1467-1473. 30. Sun, L.; Wang, S.; Tian, H., Chem. Lett. 2007, 36, (2), 250-251. 31. Tian, H.; Wang, S., Chem. Commun. 2007, (8), 781-792. 32. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Adv. Mater. 2008, 20, (10), 1998-2002. 33. Rogers, S. A.; Melander, C., Angew. Chem. Int. Ed. 2008, 47, (28), 5229-5231. 34. Pei, J. et al., J. Org. Chem. 2002, 67, (14), 4924-4936. 35. Kirschbaum, T.; Briehn, C. A.; Bäuerle, P., J. Chem. Soc., Perkin Trans. 1 2000, 8, 1211-1216. 36. Donat-Bouillud, A. et al., Chem. Mater. 1997, 9, (12), 2815-2821. 37. Sato, M. A.; Hiroi, M., Polymer 1996, 37, (9), 1685-1689. 38. Tenhoeve, W.; Wynberg, H.; Havinga, E. E.; Meijer, E. W., J. Am. Chem. Soc. 1991, 113, (15), 5887-5889. 39. Ten Hoeve, W.; Wynberg, H.; Havinga, E. E.; Meijer, E. W., J. Am. Chem. Soc. 1991, 113, (15), 5887-5889. 40. Sheina, E. E. et al., Macromolecules 2004, 37, (10), 3526-3528.  134 41. Miyakoshi, R.; Yokoyama, A.; Yokozawa, T., J. Am. Chem. Soc. 2005, 127, (49), 17542-17547. 42. Iovu, M. C.; Sheina, E. E.; Gil, R. R.; McCullough, R. D., Macromolecules 2005, 38, (21), 8649-8656. 43. Hiorns, R. C.; Khoukh, A.; Gourdet, B.; Dagron-Lartigau, C., Polym. Int. 2006, 55, (6), 608-620. 44. Chen, T. A.; Rieke, R. D., J. Am. Chem. Soc. 1992, 114, (25), 10087-10088. 45. Yue, S.; Berry, G. C.; McCullough, R. D., Macromolecules 1996, 29, (3), 933- 939. 46. Havinga, E. E.; Vanhorssen, L. W., Makromol. Chem., Macromol. Symp. 1989, 24, 67-76. 47. McCullough, R. D., Adv. Mater. 1998, 10, (2), 93-116.    135 CHAPTER 4 Reversible Amplified Fluorescence Quenching of Dithienylethene Functionalized Polythiophene∗ 4.1 Introduction The ability to convert a chemical event into measurable electrical or optical output signal is one of the main thrusts for the investigation of CPs.1 For instance, amplified fluorescent polymers (AFPs) exhibit enhanced fluorescence in response to the interactions between the CP and analytes of interest such as ions,2-7 proteins,8,9 and DNA.10-12 In these systems, the CP acts as a highly efficient transport medium (via electronic excited state quasiparticles, otherwise known as excitons) that facilitates an observed increase in sensitivity or amplification in fluorescence. The mobile excitons quickly diffuse throughout the polymer chain via mechanisms that involve both through space dipolar couplings and the strong mixing of electronic states.13-16 This phenomenon of delocalization implies that any perturbation of the electronic structure at a single point along the backbone of a CP, can be translated along the entirety of a CP chain thereby amplifying the effect of some stimulus. This effect was demonstrated by Swager et al. using an alternating copolymer which contained poly(p-phenylene ethynylene) (PPE) and bis(p-phenylene)-34-crown-10 (BPP) repeat units. The BPP behaves as an excellent receptors for paraquat, a well known electron-transfer quenching agent.1,17-19 They showed that addition of paraquat to a solution of conjugated PPE-co-BPP gave rise to a 47-66 fold enhancement in fluorescent quenching relative to a molecular model containing a single receptor unit. As illustrated  ∗  A version of this chapter has been published. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Reversible Amplifed Fluorescence Quenching of Dithienylethene Functionalized Polythiophene. Adv. Mater. 2008, 20, (10), 1998-2002.  136 in Figure 4-1, a solution that contains only single receptor units will only be quenched in a stoichiometric ratio with respect to added quencher. In a solution of polymers containing multiple receptor units along the polymer chain, the fast migration of excitons along the backbone translates into 100% of the fluorescence being quenched upon addition of one stoichiometric equivalent of quencher with respect to each polymer chain. nn Monomers Conjugated Polymer  Figure 4-1. Demonstration of amplified fluorescence quenching along a polymer backbone through binding of a quencher (●) to a receptor ( ).  In the system studied by Swager et al., fluorescence quenching was found to be dependant on the binding of an active analyte upon which the excited state was immediately quenched. For applications towards sensory systems for the detection of explosives,20-24 this high level of sensitivity is appropriate. However, if the binding is highly favourable (i.e. the binding constant is high), then loss of analyte from the binding site is unlikely. This may have drawbacks towards using such a system for repetitive analyses. Hence, it is of interest to develop systems that not only provides a fully  137 reversible quenching process, but also could be modulated between on/off states very quickly and without any physical manipulation of the system. Compounds that are responsive to external stimuli such as heat or light, rather than a chemical binding event are appealing for materials applications. The thermal irreversibility, and fatigue resistance of DTEs make them particularly interesting as molecular switches, functioning with true on/off capabilities. The DTE moiety has already shown promising results for applications in OLEDs,25 OPVs,26 and memory media.27 In this chapter, modification of a PT backbone with the DTE moiety was carried out in order to investigate the influence of the photo-induced isomerisation on the optical and electronic properties of the CP backbone. Absorption and emission studies have been used to monitor the ring-opening/closing reaction, and are discussed with respect to amplification along the CP backbone.   138 4.2 Experimental 4.2.1 General Solution electronic absorption spectra were obtained on a Varian Cary 5000 or Varian Cary 300 Bio UV-vis spectrophotometer in reagent grade C6H6 and HPLC grade CH2Cl2. Fluorescence measurements were made on a PTI QM-2000-4 scanning spectrofluorometer in the same solvent used for the corresponding UV-vis measurements. Absolute fluorescence quantum yield measurements were recorded on a PTI QM-2006-4 cw spectrofluorometer equipped with a CGM9-2-2006 integrating sphere and operated with the Felix32 software package. All samples for fluorescence measurements were excited with 470 nm irradiation. In order to improve the emission S/N ratio, an even-pass filter was placed in the light path when detecting only the excitation wavelength range, which is required to measure the number of light quanta absorbed by the sample by subtraction of sample from blank light intensity. The use of the filter ensured that similar light intensities were detected by the instrument for both excitation and emission scans so that an identical instrument configuration was maintained for both. The decrease in light intensity for the excitation scan was subsequently corrected for in the final quantum yield calculation.    139 4.3 Results and Discussion 4.3.1 Absorption and Emission Studies In order for the DTE to behave as a molecular switch, it was necessary for the DTE to electronically interact with the CP in only one of the two isomeric forms. The particular DTE derivative incorporated into Poly-4 was chosen based on two main criteria. First, the absorption band of the PT backbone had to lie in a spectral region where both DTE isomers (open and closed) were transparent. This allowed the polymer to be independently photoexcited without causing ring-opening or closing. Secondly, emission from the polymer had to overlap with the absorption band of only one of the DTE isomers (either open or closed) to provide only one pathway through which the two species could interact electronically. Absorbance studies of model compound 68 (Figure 4-2) were compared to those reported previously for DTE-37.28 The absorption maxima (λmax) for the open isomer (294 nm) and the closed form (592 nm), are shifted only very slightly from those of DTE-37. This demonstrates that formation of the triazole ring does not significantly affect the electronic structure of either isomer of DTE-37. The data in Figure 4-2 clearly demonstrates that the absorption and emission spectra of Poly-2 (λmax = 440 and 575 nm respectively), fulfill the criteria given above. Namely, the emission of Poly-2 overlaps only with the absorbance of the ring-closed isomer of DTE, and the main polymer absorption clearly lies between the open and closed absorption bands of the DTE moiety.  140 300 350 400 450 500 550 600 650 700 750 800 0 5 10 15 20 25  Em is si o n Wavelength (nm) 0.0 0.1 0.2 0.3 b) a)   Open  Closed  Ab so rb a n ce  0.0 0.4 0.8   Figure 4-2. (a) Absorption spectra of 68o (black dashed) and 68c (red dashed) and (b) absorption (black) and emission (red) spectra of Poly-2.  The photo-induced ring-closing reaction of Poly-4 is easily monitored by UV-vis absorption spectroscopy (Figure 4-3). Irradiation of a benzene solution of Poly-4o with 310 nm light results in an immediate decrease in the intensity of the absorption band at 290 nm and the appearance of a new absorption band at 595 nm. These spectral changes correspond to the disappearance of the ring-open isomer and the concurrent appearance of the ring-closed isomer. This ring-closing reaction can also be visually observed as the colour of the solution changes from orange to green. There is no change observed in the PT absorption band at 440 nm, showing it is unaffected by irradiation at this wavelength.   141 400 600 800 0.0 0.1 0.2  900 s 0 sA bs o rb a n ce Wavelength (nm)  Figure 4-3. UV-vis absorption spectra of a C6H6 solution of Poly-4, with irradiation at 310 nm.  There is significant spectral overlap between the absorbance of the ring-closed isomer 68c and the emission of the PT backbone. This implies that intramolecular quenching of the PT excited state via energy transfer should be efficient in Poly-4c, resulting in a decrease in emission relative to the ring-open form, Poly-4o. The change in emission that accompanies the photo-induced ring-closing reaction of Poly-4o is shown in Figure 4-4. The conversion of the ring-open isomer Poly-4o to its ring-closed counterpart (Poly-4c) results in efficient fluorescence quenching and virtually no emission is observed when the PSS is reached. Additionally, continuous irradiation of Poly-4 with 440 ± 5 nm light over a period of one hour caused no change in the  142 absorption spectrum, confirming that the polymer fluorescence and the ring-closing events can be accessed individually.29 600 800 0 5 10 15 20 900 s 0 s  Em is si o n Wavelength (nm)  Figure 4-4. Emission spectra of a C6H6 solution of Poly-4, with irradiation at 310 nm.  An overview of the maximum absorption and emission wavelengths for each analog of Poly-4 is presented in Table 4-1. In general, the data display similar values for the absorption and emission maxima within a polymer series. This demonstrates that changing functional groups (i.e. from bromide, to azide, and finally to DTE) does not inherently affect the conjugated backbone. It is also observed that in general the maximum absorption shifts to longer wavelengths as the average polymer chain length  143 increases. This corresponds to the SEC data presented in Chapter 3 and corroborates the extension of conjugation along the polymer backbone.  Table 4-1. UV-vis absorption and emission data from different polymer species Compound Absorption   λmax (nm) Absorptiona λmax (nm) Emissionb λmax (nm) w (g mol-1) 68 293 276, 313, 590 - - 70 350 - 423, 440 - 71 298, 350 350, 596 422, 440 - Poly-2 440 - 573 12000 Poly-4 290, 444 444, 592 574 16000 Poly-5 411 - 565 4400 Poly-6 411 - 564 4700 Poly-7 289, 421 421, 595 564 6300 Poly-8 427 - 568 7300 Poly-9 427 - 567 15000* Poly-10 428 - 568 5400 Poly-11 430 430, 600 568 6000 For derivatives containing DTE: a Ring closed; b Measured in the Ring Open State. * The discrepancy of this value is discussed in Chapter 3.  Both the absorbance and emission spectra of 70 are significantly blue shifted from that of Poly-2. When the absorbance spectra of the two DTE isomers (68) were compared to the absorbance and emission data for compound 70 (Figure 4-5), the spectra display poor overlap of the emission of 70 with the absorbance of the ring-closed isomer (68c), relative to the overlap in Poly-2. As well, the absorbance band of 70 does not lie between the absorbance band of the ring-open and closed forms but has significant overlap with the absorbance of 68c at higher energy.   144 0.0 0.1 0.2 0.3 b) a)   OPEN  CLOSED  Ab so rb a n ce 300 400 500 600 700 800 0.0 0.2 0.4 0.6 0.8 Wavelength (nm)  0 5 10 15 Em is si o n  Figure 4-5. (a) Absorbance spectra of 68o (black dashed) and 68c (red dashed) and (b) absorbance (black) and emission (red) of 70.  A decrease in the emission from 71 at 440 nm is still expected as the concentration of 71c increases with irradiation. In fact, irradiation of a benzene solution of 71o with 302 nm light results in an immediate decrease in the absorbance band at 298 nm, an increase in the absorbance band at ~ 600 nm, and a decrease of the emission at ~ 440 nm (Figure 4-6).  145 300 400 500 600 700 800 0.0 0.5 1.0 1.5 2.0 900 s 0 s a)  Ab so rb a n ce Wavelength (nm) 400 450 500 550 600 0 10 20 30 40 0 s 900 s b)  Em is si o n  Figure 4-6. (a) UV-vis absorption and (b) emission spectra of the photo-induced ring closing reaction of a C6H6 solution of 71 upon irradiation with a 302 nm lamp.  In the absorption spectrum of 71o, a shoulder is observed at 350 nm corresponding to the absorbance for 70, and is attributed to the terthiophene group.  Upon irradiation of 71o, this absorption band appears to increase. Irradiation with light greater in wavelength than 530 nm results in the ring-opening reaction, returning 71c to 71o with complete regeneration of the original absorbance at 350 nm. An isobestic point appears at 320 nm, indicating that the irradiation results only in conversion of 71o to 71c, and not to formation of unwanted side products. The lack of formation of a significant amount of side products is also demonstrated in the cycling experiment depicted in Figure 4-7. The maximum absorptions at 295 and 595 nm, as well as the maximum emission intensity at 440 nm were monitored over 10 ring-opening/closing cycles. There is little change in the  146 intensity of the absorption maximum between successive irradiations confirming that the photo-induced isomerisation is not leading to a degradation of the sample. 2 4 6 8 10   In te n si ty  (a. u . ) Number of Cycles      Figure 4-7. Monitoring the change in absorbance and emission intensity of 71 over 11 ring-opening and ring-closing cycles. Absorbance monitored at 298 nm (), and 595 nm (). Emission monitored at 440 nm ().  Absorption and emission studies as a function of irradiation time were also carried out on benzene solutions of Poly-7 and Poly-11. The ring-closing reactions in both of these polymers were induced by irradiation at 302 nm. In the absorption spectrum of Poly-7o (Figure 4-8a), there are a few significant differences observed in comparison to Poly-4o. The most significant difference is the large hypsochromic shift in the absorption due to the polymer backbone (λmax = 421 nm for Poly-7 compared λmax = 440 nm for Poly-4). As discussed in Chapter 2, the extent of backbone conjugation is related to the  147 energy of the pi−pi* transition in the absorption spectrum. Here, λmax is closer to that observed for regio-irregular P3HT derivatives (50% HT couplings), reported to have λmax = 428 nm.30 While these data are indicative of a loss of regioregularity along the polymer backbone in Poly-7, a blueshift relative to Poly-4 is also expected due to reduction in the average polymer chain length. In fact, the 1H NMR spectrum of Poly-7 indicates a somewhat lower degree of regioregularity (~ 70% HT for Poly-7 versus 85% HT couplings within Poly-4). However, this does not appear to dramatically affect the extent of fluorescence quenching along the polymer backbone such that the polymer fluorescence is still observed to be quenched to 95% of its original intensity. 400 600 800 0.0 0.2 0.4 0.6 0.8 1.0 1.2  Ab so rb a n ce Wavelength (nm) a) 0 s 90 s 500 600 700 0 2 4 6 8 10 12 14    Em is si o n 0 s 90 s b)  Figure 4-8. (a) UV-vis absorption and (b) emission spectra of the photo-induced ring closing reaction of a C6H6 solution of Poly-7 upon irradiation with a 302 nm lamp.    148 In addition, the ratio of the absorbance at λmax of the ring-closed isomer (600 nm) to that of the polymer backbone (at 421 nm) changes from 69% in Poly-4 to 93% in Poly-7. This indicates a higher amount of DTE is present in Poly-7, confirmed by the 3:2 ratio of hexyl:DTE groups (from 1H NMR spectroscopy). In the emission studies of Poly-7o (Figure 4-8b), there is a large decrease of emission intensity directly corresponding to the increase in absorption of the ring-closed Poly-7c. As expected, there is a substantial amount of overlap between the absorbance of the ring-closed form Poly-7c and the emission of Poly-7o. Absorbance and emission studies of Poly-11 showed several differences when compared to studies of Poly-4 and Poly-7. Due to the very low amount of DTE in Poly- 11, it was necessary to study the ring-closing reaction at a much higher optical density with respect to the polymer backbone than for the other polymers. As shown in Figure 4-9a, irradiation of a benzene solution of Poly-11 at 302 nm shows an increase in absorbance at ~ 600 nm and an isobestic point at 340 nm.  The slight shift of the polymer backbone absorbance from 440 nm in Poly-4 to ~ 430 nm in Poly-11 appears to be of little consequence to the ring-closing reaction.  149 300 400 500 600 700 800 0.0 0.2 0.4 0.6 0.8 1.0 40 s 0 s b)a)  Ab so rb a n ce Wavelength (nm) 500 600 700 0 5 10 15 40 s 0 s  Em is si o n   Figure 4-9. (a) UV-vis absorption and (b) emission spectra of the photo-induced ring closing reaction of a C6H6 solution of Poly-11 upon irradiation with a 302 nm lamp.  The emission of Poly-11 occurs at λmax = 567 nm (Figure 4-9b). This falls between the observed λmax values for Poly-4 and Poly-7. The overlap between the emission and the absorbance of the ring-closed form in Poly-11 is favourable for fluorescence quenching, yet the extent of quenching is highly reduced relative to Poly-4. The emission observed at the PSS of the ring-closing reaction is still 68% of the original intensity.  150 4.3.2 Fluorescence Quenching and Amplification Fluorescence quenching was observed for Poly-4 and each of its analogs (71, Poly-7 and Poly-11). To measure the extent of fluorescence quenching and to establish the effective amplification of the quenching, each sample was compared to a solution containing the un-tethered precursors to Poly-4; Poly-2 and DTE-37. This solution was prepared in concentrations that replicate the optical density of Poly-4 in solution such that the absorbance spectra for Poly-2/DTE-37o and Poly-2/DTE-37c, were nearly superimposable with those for Poly-4o and Poly-4c (Figure 4-10).  400 600 800 0.00 0.05 0.10 0.15 0.20 0.25 b)a)   Ab so rb a n ce Wavelength (nm) 600 800 0 5 10 15 20   Em is si o n   Figure 4-10. (a) Absorption and (b) emission spectra of Poly-4 (open: black solid lines, closed: black dotted line) and Poly-2/DTE-37 (open: red solid lines, closed: red dotted line).   151 The data in Figure 4-11 displays the absorbance values corresponding to the ring- closed systems at 595 nm plotted versus irradiation time. They indicates that both solutions approach the PSS (900 s) at the same rate. The percentage of ring-closed isomer present at the PSS is 96% for both systems as measured using 1H NMR spectroscopy. 0 200 400 600 800 1000 1200 1400 0.00 0.05 0.10 Ab so rb a n ce  Time (s) 0.0 0.2 0.4 0.6 0.8 1.0 N o rm a liz e d Em is si o n  (F /F 0)  Figure 4-11. Changes in absorbance (λmax = 595 nm) of Poly-4c () and Poly-2/DTE- 37c (), and changes in emission (λmax  = 575 nm) of Poly-4o () and Poly-2/DTE-37o () upon approaching the PSS.  Figure 4-11 also reveals that fluorescence quenching by the covalently bound DTE of Poly-4c differs dramatically from that of the Poly-2/DTE-37c mixture. At the PSS, the emission of Poly-4 has been quenched 99% relative to the emission intensity of the ring-open isomer. The control solution has only been reduced by 12% of its original intensity. This difference may be studied using a Stern-Volmer analysis. The Stern-  152 Volmer relationship describes the variations of photophysical (e.g. fluorescence and phosphorescence) intermolecular deactivation processes represented by the equations:  A* + Q  A + Q      Eq. 4-1 A* + Q  A + Q*     Eq. 4-2  where A is the chromophore and Q is a quencher. In the simplest case, the change in emission is linearly related to the concentration of available quencher. Here, the effective concentration of quencher (closed DTE) is much higher in Poly-4 than in the solution Poly-2/DTEc where the quenching species is not attached. Quantum yield (Φ) measurements were made to further quantify the extent of fluorescence quenching in Poly-4 compared to that of the Poly-2/DTE-37 mixture. The quantum yield decreases from 0.25 for Poly-4o to 0.003 for Poly-4c. The values measured for Poly-2/DTE-37o and Poly-2/DTE-37c were 0.31 and 0.19, respectively. These values display a quenching efficiency for Poly-4 of 99% and only 39% for that of the Poly-2/DTE-37 mixture. Closer inspection reveals that the increased quenching efficiency of Poly-4c is amplified along the CP backbone. In Figure 4-12, the normalized emission (emission relative to that of the ring-open isomer) is plotted as a function of effective concentration of ring-closed isomer (measured absorbance at 595 nm, normalized to the PSS). In the case of the Poly-2/DTE-37 mixture there is a nearly linear dependence on the decrease of emission with the related increase in ring-closed DTE concentration. In terms of the Stern-Volmer relationship, this is the behaviour expected for an intermolecular quenching  153 process. The non-linear dependence seen for Poly-4 clearly demonstrates the amplification of a low concentration of ring-closing events on the emission of the polymer. 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0   N o rm a liz e d Em is si o n  (F /F 0) Normalized Absorbance (A/APSS)  Figure 4-12. Normalized emission, F/F0 (λmax = 575 nm), as a function of normalized absorbance, A/APSS (λmax = 595 nm), for the C6H6 solutions of Poly-4 () and Poly- 2/DTE-37 ().  The amplification is attributed to the rapid migration of initially formed excitons along the polymer backbone rendering further quenching events unproductive. It is expected that at low concentrations of ring-closed DTE, fluorescence quenching would still obey the Stern-Volmer relationship. To verify this, the initial induction period of  154 fluorescence quenching was examined with shorter irradiation times,29 intended to drive the photo-induced ring-closing reaction to only 4% of the PSS. At this concentration, the ring-closed DTE groups are statistically distributed throughout the polymer chain, where they can quench the fluorescence without interfering or overlapping with each other, affording a ‘cleaner’ effect. As depicted in Figure 4-13 there is a linear relationship between the concentration of the ring-closed DTE and polymer emission intensity. 0.00 0.01 0.02 0.03 0.04 0.8 0.9 1.0   N o rm a liz e d Em is si o n  (F /F 0) Normalized Absorbance (A /APSS)  Figure 4-13. Initial induction of fluorescence quenching experienced by Poly-4 with shorter irradiation times.29    155 This induction period was used as a measure of the efficiency of the fluorescence quenching along the CP. Taking the average molecular weight (w) of the polymer chain (16000 g mol-1) determined from SEC, and the molecular weight of the monomer unit determined by 1H NMR from the ratio of monomers within the chain (2:1; hexyl:DTE), the number of repeat units was estimated. An average chain was determined to contain approximately 15 repeat units, corresponding to 15 DTE moieties within a polymer chain containing ~ 45 thiophene rings. Extrapolation of the data in Figure 4-13 to zero fluorescence (100% quenching) results in a necessary concentration of 14% of the DTE moieties to reach the PSS which correlates to the ring-closing of only two DTE units. Therefore, with two DTE units contributing to 100% fluorescence quenching, the average exciton migration was determined to occur along ~ 20 thiophene units agreeing well with previous estimates.31 The comparison between each of the DTE functionalized analogs of Poly-4 with respect to their individual effectiveness for fluorescence quenching is shown in Figure 4-14, where normalized emission (relative to the emission of the ring-open isomer) is plotted as a function of ring-closed isomer (measured at the absorbance at 595 nm, normalized to the PSS).  156 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0   N o rm a liz e d Em is si o n  (F /F 0) Normalized Absorbance  (A/APSS)  Figure 4-14. Comparison of amplified fluorescence quenching for Poly-4 (), Poly- 2/DTE-37 (), Poly-7 (), Poly-11 () and 71 ().  The two extremes of fluorescence quenching are demonstrated by the control solution Poly-2/DTE-37 with a linear dependence on quencher concentration and Poly-4, which demonstrates non-linear or amplified fluorescence quenching. The next most effective quenching system is observed to be Poly-7 (), where (at the PSS) the emission is determined to be 96% quenched. This is to be expected for the polymer whose structure closely resembles the backbone structure of Poly-4. However, there is a slight decrease in overall quenching efficiency of Poly-7 compared to Poly-4 and this  157 may relate to the slight decrease in HT regioregularity in the polymer backbone of Poly-7 leading to a higher degree of breaks in conjugation. The next most efficient fluorescence quenching is observed in the terthiophene analog, compound 71 (). The gradual decrease in emission approaches linearity but still trends toward 100% fluorescence quenching. The lack of amplification results from the significantly shorter backbone, which eliminates the necessity for long range exciton migration. The terthiophene species effectively behaves as a solution of monomeric receptors (Figure 4-1) where one DTE moiety can fully quench the fluorescence of the terthiophene oligomer it is tethered to. The quenching efficiency of 71 is higher than that of the control solution Poly-2/DTE-37 due to the close proximity of a covalently bound DTE unit to the terthiophene backbone. By comparison, the quenching efficiency of Poly-2/DTE-37 relies on diffusion limited intermolecular quenching. Finally, the block copolymer Poly-11 is not observed to reach the fully quenched fluorescent state, reaching only 68% of the original fluorescent intensity. This reduction of fluorescence quenching is believed to be due to the block structure of the polymer. Results from the SEC analysis show that the final average molecular weight of Poly-11 is approximately 6000 g mol-1. If one assumes a 10:1 ratio of hexyl:DTE content, the average polymer chain contains approximately 30 hexylthiophene units to three DTE moieties. From the average exciton migration length calculated for Poly-4, it appears that the average length of Poly-11 is too long for the excitons at one end of the polymer to reach the other.   158 4.4 Conclusions Functionalization of a HT regio-regular PT with a pendant DTE photoswitch demonstrates efficient fluorescence quenching via energy transfer from the excited state of the PT backbone to that of the ring-closed DTE absorption. Amplification of fluorescence quenching is observed for Poly-4 and Poly-7, the two analogs with extended conjugation allowing for efficient migration of excitons along the polymer backbone. The migration of excitons along a CP backbone is shown to have a limit in path length, displayed by the inefficient fluorescence quenching of Poly-11. This block copolymer has an average chain length approximately 30 thiophene units long which extends beyond the experimentally determined migration length of 20 thiophenes. The linear quenching dependency observed for compound 71 reinforces the need for long range conjugation throughout the length of the polymer backbone in order for an amplified effect to be observed.  159 4.5 References 1. Thomas, S. W.; Joly, G. D.; Swager, T. M., Chem. Rev. 2007, 107, (4), 1339- 1386. 2. Kim, T. H.; Swager, T. M., Angew. Chem. Int. Ed. 2003, 42, (39), 4803-4806. 3. Tang, Y. L. et al., Macromol. Rapid Commun. 2006, 27, (6), 389-392. 4. Huang, H. M. et al., Angew. Chem. Int. Ed. 2004, 43, (42), 5635-5638. 5. Ramachandran, G. et al., J Fluoresc 2003, 13, (5), 427-436. 6. Kim, J.; McQuade, D. T.; McHugh, S. K.; Swager, T. M., Angew. Chem. Int. Ed. 2000, 39, (21), 3868-3872. 7. Wang, B.; Wasielewski, M. R., J. Am. Chem. Soc. 1997, 119, (1), 12-21. 8. Kumaraswamy, S. et al., Proc. Natl. Acad. Sci. USA 2004, 101, (20), 7511-7515. 9. Rininsland, F. et al., Proc. Natl. Acad. Sci. USA 2004, 101, (43), 15295-15300. 10. Ho, H. A.; Béra-Abérem, M.; Leclerc, M., Chem. Eur. J. 2005, 11, (6), 1718- 1724. 11. Bernier, S. et al., J. Am. Chem. Soc. 2002, 124, (42), 12463-12468. 12. Ho, H. A. et al., Angew. Chem. Int. Ed. 2002, 41, (9), 1548-1551. 13. Brédas, J. L. et al., Acc. Chem. Res. 1999, 32, (3), 267-276. 14. Schwartz, B. J., Annu. Rev. Phys. Chem. 2003, 54, 141-172. 15. Kim, J.; Levitsky, I. A.; McQuade, D. T.; Swager, T. M., J. Am. Chem. Soc. 2002, 124, (26), 7710-7718. 16. Levitsky, I. A.; Kim, J.; Swager, T. M., Macromolecules 2001, 34, (7), 2315- 2319. 17. Zhou, Q.; Swager, T. M., J. Am. Chem. Soc. 1995, 117, (50), 12593-12602.  160 18. Zhou, Q.; Swager, T. M., J. Am. Chem. Soc. 1995, 117, (26), 7017-7018. 19. Allwood, B. L. et al., J. Chem. Soc., Chem. Commun. 1987, (14), 1064-1066. 20. Rose, A.; Lugmair, C. G.; Swager, T. M., J. Am. Chem. Soc. 2001, 123, (45), 11298-11299. 21. Wosnick, J. H.; Liao, J. H.; Swager, T. M., Macromolecules 2005, 38, (22), 9287- 9290. 22. Yamaguchi, S.; Swager, T. M., J. Am. Chem. Soc. 2001, 123, (48), 12087-12088. 23. Yang, J. S.; Swager, T. M., J. Am. Chem. Soc. 1998, 120, (46), 11864-11873. 24. Yang, J. S.; Swager, T. M., J. Am. Chem. Soc. 1998, 120, (21), 5321-5322. 25. Zacharias, P. et al., Angew. Chem. Int. Ed. 2009, 48, (22), 4038-4041. 26. Tsujioka, T.; Masui, K.; Otoshi, F., Appl. Phys. Lett. 2004, 85, (15), 3128-3130. 27. Myles, A. J.; Branda, N. R., Adv. Funct. Mater. 2002, 12, (3), 167-173. 28. Myles, A. J.; Wigglesworth, T. J.; Branda, N. R., Adv. Mater. 2003, 15, (9), 745- 748. 29. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Adv. Mater. 2008, 20, (10), 1998-2002. 30. Chen, T. A.; Wu, X. M.; Rieke, R. D., J. Am. Chem. Soc. 1995, 117, (1), 233-244. 31. Kishino, S. et al., Phys. Rev. B 1998, 58, (20), 13430-13433.     161 CHAPTER 5 Electrodeposition of TEMPO Functionalized Polythiophene Thin Films∗ 5.1 Introduction Organic materials capable of reversibly storing charge are of significant interest for use in devices such as batteries1,2 or supercapacitors.3-7 These materials offer several key advantages over traditional inorganic battery materials. They are low weight, offer mechanical flexibility and are compatible with solution based processing techniques such as spin-coating8,9 and ink-jet printing.10-12 Conjugated polymers (CPs) have been investigated as potential battery materials13 as they possess many desirable characteristics for this application:  they can be reversibly doped, can be prepared in thin-film form, and can be made soluble via substituents on the polymer backbone. However, CPs often exhibit low doping levels, resulting in small redox capacities, and slow kinetics at the electrode often limit the charging and discharging rates of  the resulting device.14 Scheme 5-1 N O R N O R N O R + e- - e- nitroxyl radical 56 49 57 + e- - e- oxammonium cation deprotonated hydroxylamine   An alternative approach involves the use of redox polymers where discrete moieties, which undergo reversible redox processes, are attached to a polymer backbone  ∗  A version of this chapter will be submitted for publication. Kunz, T. K. and Wolf, M. O., Electrochemical Thin Film Deposition of TEMPO Functionalized Polythiophenes.  162 and can be used to store charge. Promising candidates for charge storage are stable radical species. An important aspect of these robust radicals is their electrochemical reversible redox properties.14 A neutral radical (R·) can be oxidized to the cation (R+) or reduced to an anion (R-). Electrochemical reversibility is dependant on stability of the parent R· , and the closed shell products R+ and R- (Scheme 5-1) Nitroxide radicals, contain a >N-O group upon which the unpaired electron spin density is located.15 A key feature for the stability of the nitroxide radical TEMPO, is the absence of α-hydrogen atoms. If one or more are present, the radical will undergo disproportionation to form a hydroxylamine (54) and the corresponding nitrone (55) (Scheme 5-2). Scheme 5-2 R N O H R N OH H R N O +2 555453   TEMPO (49) has found widespread applications as a catalyst for the oxidation of alcohols,16-19 as a biological radical scavenger,20,21 and as a mediator in living free radical polymerizations.22,23 TEMPO has also been used as a pendant group on polynorbornene polymers.1,2  Due to its rapid and stoichiometric reversible redox processes,24-26 it offers high-charging and discharging rates, making it potentially useful in battery applications. Here, a new PT functionalized with pendant TEMPO radicals is prepared and discussed. This material can take advantage of the redox capabilities of both the TEMPO and PT backbone to potentially increase the charge stored per unit weight. Investigations of this potential charge storage capacity are presented and discussed.  163 5.2 Experimental 5.2.1 General All reagents and solvents were used as received except where noted. Tetrahydrofuran (THF) was distilled from Na/benzophenone. Anhydrous dimethylformamide (DMF) was distilled from P2O5. Compound 74 was prepared according to the literature.17 O N O 74   1H NMR spectra were obtained in CDCl3 either on a Bruker AV- 400 Inverse or a Bruker AV-400 Direct spectrometer. Chemical shifts are reported in ppm, referenced to residual chloroform (CHCl3) (δ 7.27). ATR-IR spectra were recorded on a Thermo Scientific Nicolet 6700 FT-IR spectrometer as neat powders or oils. Electronic absorption spectra were obtained on a Varian Cary 5000 UV-vis spectrometer in HPLC grade CH2Cl2 and CHCl3. Fluorescence measurements were made on a PTI Quantamaster spectrometer in the same solvents used for UV-vis measurements. Molecular weight distribution curves of polymers were determined by size exclusion chromatography (SEC) was performed using a Waters SEC equipped with 3 µg-Styrgel columns against polystyrene standards.  Polymers were dissolved, filtered and eluted with THF at a flow rate of 1.0 mL/min and monitored with a UV-vis detector (Waters 2487). Data was acquired and analyzed using an IBM personal computer and custom-written software. Electrochemical measurements were conducted on a Autolab PGSTAT12 using either a  164 Pt disk, ITO plated glass or microporous carbon paper working electrode, Pt mesh counter electrode, and a Ag wire reference electrode. These measurements were made in CH2Cl2 passed through an alumina column, acetonitrile (ACN) distilled over molecular sieve (type 3A, 4-8 mesh beads) or propylene carbonate obtained from Aldrich (sure- seal). Unless specified, measurements were referenced against the pseudo-reference Ag wire. Alternatively, an internal reference (decamethylferrocene) was added to correct the measured potentials with respect to saturated calomel electrode (SCE). The 0.1 M [n- Bu4N]PF6 supporting electrolyte was purified by triple recrystallization from ethanol and dried at 90ºC under vacuum for 3 days. Electron Spin Resonance (ESR) spectra were obtained using an Bruker Elexys E-500, X-band (9.5 GHz) spectrometer. Samples were measured as benzene solutions.  165 5.2.2 Procedures Synthesis of Poly-12 S S N N N O C6H13 N O x y {x:y; 1:2} n  Poly-227 (0.0615 g, 0.127 mmol) and acetylene functionalized TEMPO (74) (0.0271 g, 0.129 mmol) were dissolved in THF  (10 mL) resulting in an orange solution which was degassed with N2 (20 min). CuI (0.0044 g, 0.023 mmol) was added to the stirring solution in one portion. The reaction mixture was covered in Al foil and the solution was heated to 100 ºC. The vigorously stirring solution was left overnight and then cooled to allow precipitation of a purple solid from methanol (600 mL). Poly-12 was then re-precipitated twice from methanol. Yield: 0.052 g (59%). 1H NMR (400 MHz, CDCl3, δ): 7.01 (br, s), 2.81 (br, s), 1.8 – 1.2 (m), 0.91 (m). ATR-IR (ν, cm-1): 2961, 2923, 2853, 1456, 1376, 1361, 1259, 1219, 1175, 1081, 1015, 863, 795, 669, 569. UV-vis (CH2Cl2) λmax: 435 nm. Fluorescence (CH2Cl2) λmax: 575 nm. SEC: w = 13500, n = 8500, PDI = 1.5.  166 5.3 Results and Discussion 5.3.1 Synthesis and Characterization The modification of a HT regioregular polymer (prepared through the GRIM polymerization) via attachment of a stable free radical was carried out to investigate the potential charge storage capabilities of a coupled organic redox group and a CP. Poly-12 was synthesized using Click chemistry to modify a previously prepared polymer, Poly- 2,27 with an acetylene modified TEMPO radical (74) as shown in Scheme 5-3. Previously,27 the Click reaction was carried out using CuSO4.5H2O and L-ascorbic acid to generate the active catalyst CuI from CuII in-situ. It has been demonstrated that nitroxyls of the piperidine series can be oxidized by CuII in solution.28,29 To avoid any complications with the reactivity of the catalyst, Cu(I)iodide was used in place of CuSO4.5H2O and ascorbic acid.17,30 The final polymer was isolated and purified via multiple re-precipitations from methanol. Scheme 5-3 S S N N N O C6H13 N O x y S S N3 O C6H13 N O x y + 25 mol% CuI CHCl3/DMF Poly-2 Poly-12 74 {x:y; 1:2} {x:y; 1:2} n n   167 Poly-12 was characterized by ATR-IR, UV-vis, fluorescence, 1H NMR, and ESR spectroscopy.  In the ATR-IR spectrum, the azide stretching band of Poly-2 at 2091 cm-1 disappears. In addition, there are no acetylene stretches present at 3229 or 2111cm-1. This suggests that the azide and acetylene starting materials have reacted. TEMPO lacks a distinct IR handle for confirmation of its presence; closer inspection of the fingerprint region of the IR spectra was necessary (Figure 5-1). A stretching band observed at 1361 cm-1 is within the characteristic range of the NO· moiety (1340–1390 cm-1)15,31 and supports the presence of the free radical. Further support of this assignment is obtained from a stretching frequency at 1365 cm-1 observed for the TEMPO precursor, 74, and the lack thereof in Poly-2. 1500 1450 1400 1350 1300 1250 1200 60 80 100 120 1365 cm-1 1361 cm-1* *  % Tr a n sm is si o n Wavenumber (cm-1)  Figure 5-1. IR spectra of Poly-12 (green), Poly-2 (red), and 74 (black) displaying the fingerprint region. (*) indicates the ν(NO·) stretching frequency.   168 Absorbance and emission studies were carried out in CH2Cl2 solution ( Figure 5-2). The absorbance maximum of Poly-12 is observed at 436 nm displaying a minimal shift compared to that of Poly-2 (λmax = 437 nm). Poly-12 also exhibited an emission maximum at 575 nm, directly corresponding to the emission wavelength of Poly-2. Interestingly, there is a significant reduction in fluorescence intensity for Poly-12 compared to that of Poly-2 when the two compounds were studied in CH2Cl2 solutions of the same optical density. The significant emission quenching observed in Poly-12 can be rationalized by electron transfer between the TEMPO group and the excited state of the polymer backbone. In fact, the TEMPO group is commonly used as a one electron acceptor in fluorescence quenching experiments.32,33 The fluorescence has not been completely quenched and is attributed to the concentration of TEMPO groups being too low to fully quench the system. 400 500 600 700 800 Ab so rb a n ce Wavelength (nm) Em is si on  Figure 5-2. Absorption and emission spectra of CH2Cl2 solutions of Poly-2 (black) and Poly-12 (red).  169 The 1H NMR spectrum of Poly-12 displays significantly broadened signals, as expected for a polymeric radical-containing material.34 The only protons that could be resolved were observed from δ 2.80 to 0.91 are assigned to the protons of the hexyl groups corresponding in chemical shift with similar resonances in Poly-2. 5.3.2 Electron Spin Resonance Studies Systems that contain one or more unpaired electrons result in line broadening in NMR spectroscopy.34 Electron spin resonance (ESR) spectroscopy is a technique used specifically to study such paramagnetic systems. ESR spectroscopy was carried out on Poly-12 to further confirm the presence of the TEMPO moiety (Figure 5-3). The nitroxide free radical is known to show a triplet hyperfine structure due to the interaction between the nuclear spin of 14N (I = 1), and the electron spin of the free radical (I = ½) according to the equation 2nI + 1, where n is the number of nuclei and I is the spin state of that nucleus.35,36 The ESR spectrum of Poly-12 in a benzene solution at room temperature shows a triplet centered at 3504 G, characteristic of TEMPO derivatives, confirming that the radical is present in Poly-12.37  170 3450 3500 3550 -10 -5 0 5 10  Field (G) In te n si ty  (a. u . )  Figure 5-3. X-band ESR spectrum of Poly-12 in C6H6 solution at 22 °C. Modulation Frequency: 20.00 kHz. Modulation Amplitude: 0.02 G. Time Constant: 2.56 s. Gain: 60 dB. Sweep Width: 150.6 G.  5.3.3 Cyclic Voltammetry Studies Poly-12 was studied using cyclic voltammetry (CV) using indium tin oxide (ITO) coated on glass and high surface area microporous carbon paper working electrodes. In the studies of Poly-12 carried out on ITO coated glass slides, the first scan (Figure 5-4a) of the voltammogram in CH2Cl2 displays an oxidation wave at 1.28 V (vs. Ag wire) due to oxidation of TEMPO with the corresponding reduction wave observed at 1.06 V (vs. Ag wire). Interestingly, sequential scans exhibit increasing current (Figure 5-4b). This behaviour is characteristic of conducting polymer deposition on an electrode and is typically observed in monomers which polymerize electrochemically.  171 0.0 0.5 1.0 1.5 2.0 -150 -75 0 75 150 225 a)   Cu rr e n t (µ A)  Potential (V) vs Ag Wire 0.0 0.5 1.0 1.5 2.0 2.5 -150 -75 0 75 150 225 b)   Cu rr e n t (µ A)  Figure 5-4. (a) Initial scan and (b) polymerization of Poly-12 on ITO. 0.1 M [n- Bu4N]PF6 in CH2Cl2 on ITO coated glass working electrodes. Scan rate = 50 mVs-1.  This growth phenomenon has not been previously reported for preformed CPs. The same polymer growth was displayed by the precursor polymer Poly-2, demonstrating that it was not an isolated effect caused by inclusion of the TEMPO moiety. As seen in Figure 5-5, the redox wave of the TEMPO group seems to overlay the features of the growing polymer, with a noticeable shift of the TEMPO redox wave to higher potential.   172 0.0 0.5 1.0 1.5 2.0 -150 -75 0 75 150 225   Cu rr e n t (µ A) Potential (V) vs Ag Wire 0.0 0.5 1.0 1.5 2.0 -40 -20 0 20 40 60 80  Cu rr e n t (µ A)    Figure 5-5. Cyclic voltammograms of the growth of Poly-12 vs. Poly-2. 0.1 M [n- Bu4N]PF6 in CH2Cl2 solutions growth on ITO coated glass electrodes. Scan rate = 50 mVs-1 .   The film was removed from the polymerization solution, washed with CH2Cl2 to remove any extraneous, undeposited polymer, and subsequently studied in polymer-free CH2Cl2 solution. Upon applying a potential scan (-0.2 V to 1.8 V) to the thin film electrode, only background current was recorded. A second film was studied in ACN solution in which the current was observed to decrease with sequential scans, indicating loss of the film from the electrode (Figure 5-6). The loss of the film was also confirmed visually with the appearance of a purple halo-like cloud forming around the electrode during the sequential scans.  173 -0.5 0.0 0.5 1.0 1.5 2.0 -0.2 0.0 0.2 0.4 Cu rr e n t (m A)  Potential (V) vs. Ag wire  Figure 5-6. Degradation of Poly-12 on ITO working electrode. 0.1 M [n-Bu4N]PF6 in ACN. Scan rate = 100 mVs-1.  Similar redox features and film instability were observed for the thin films of Poly-12 deposited on carbon paper electrodes when studied in both CH2Cl2 and ACN. The oxidation and reduction waves of the TEMPO groups were observed at 0.91 V and 0.85 V (vs. SCE) on carbon paper, respectively. Due to the larger surface area of the carbon paper electrode, passivation of the electrode surfaces didn’t occur until a higher number of scans had been reached allowing for a greater mass of polymer to be deposited. This subsequently provided enough additional mass to allow for microanalysis weight measurements to be performed. Deposited polymer masses were obtained in the range of 0.5 to 1.2 mg.  174 The carbon paper electrodes were studied in a propylene carbonate solution, where the deposited polymer films of Poly-12 were stable enough for additional measurements. Unfortunately, the ITO samples seemed to degrade in this solvent as well. The thin film of Poly-12 on the carbon paper electrode was subjected to several potential scans at various speeds (Figure 5-7). A linear increase in peak current as a function of increasing scan rate demonstrates that the redox behaviour of TEMPO is reversible and exhibits rapid electron transfer kinetics.38 0.4 0.6 0.8 1.0 1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 Cu rr e n t (m A) Potential (V) vs. SCE  Figure 5-7. Cyclic voltammogram of Poly-12 on carbon paper with increasing scan rate (Propylene carbonate, mVs-1): 25, 50, 100, 150, 200.   175 5.3.4 Capacity and Charge/Discharge Studies The samples of Poly-12 deposited on carbon paper electrodes were used to measure the capacity of the polymer films. Integration of the CV curve along the oxidation scan from 0.0 to 1.5 V yields a measure of the amount of charge that can be stored in the material over that potential range. The theoretical capacity (C; in A h kg-1) is determined from the molecular weight required per exchangeable unit charge in the polymer according to Eq. 5-1:  ( ) ( )1000MW3600/ × × = eNkgAhC A                                    Eq. 5-1  where NA × e is the Faraday constant (96,487 C mol-1), MW is the equivalent mass of the polymer in grams, and defined as the molecular weight of the repeating unit divided by the number of electrons exchanged or stored within it.39,40 The theoretical capacity of Poly-12 is calculated to be 76.5 A h kg-1 assuming that the TEMPO group can store one electron and the thiophene backbone can store one electron per three thiophene rings (the repeat unit determined from 1H NMR of Poly-2).13,41-43 The value determined for Poly-12 from the experimental data is 2.3 A h kg-1 (averaged over several samples). In contrast, samples of electrochemically synthesised PT have been observed to display a specific charge as high as 52 A h kg-1.13 These results are contrary to the expected improvement in properties afforded by the rr-PT backbone. For a more critical evaluation of the capacitance of the polymer film, galvanostatic charge and discharge cycles were carried out. The deposited film was  176 placed in a polymer free solution and with a constant applied current the potential is scanned in both a positive and negative direction within the potential range of charge storage. Figure 5-8 displays the charge/discharge curves from scans at 0.1 mA, cycled between 0.8 and 1.2 V for Poly-12. The amount of charge being stored in the film is calculated in terms of Farads per gram (F g-1). For several samples of Poly-12 grown on carbon paper electrodes, the curves led to specific capacities in the range of ~ 0.8 F g-1. By way of comparison, the charge and discharge cycles carried out on Poly-2, delivered values an order of magnitude higher at 11.3 F g-1.  Multiple samples were prepared and studied, and in all of these samples Poly-12 displayed consistently lower values than those of Poly-2. 0 200 400 600 800 1000 0.8 0.9 1.0 1.1 1.2 Po te n tia l (V ) Time (s)  Figure 5-8. Typical galvanostatic charge-discharge curve of Poly-12 scanned at 0.1 mA in propylene carbonate with 0.1 M [n-Bu4N]PF6 supporting electrolyte. Scanned between 0.8 – 1.2 V.   177 5.3.5 Backbone Oxidation A dramatic decrease of polymer electroactivity was observed after the first cycle of the galvanostatic charge-discharge experiment, with continued degradation observed for each sequential scan (Figure 5-8). Each of the samples of Poly-12 exhibited this same behaviour. This pronounced degradation and the unsatisfactory specific charge and capacity measurements obtained for Poly-12, led to investigations into the possible causes of degradation. A potential explanation lies in the possibility of breaks in the conjugation along the polymer chain. This may be the result of mechanical strain provoked by the ions during insertion and deinsertion44 or chemical attack by the solvent, doping ions or water contained in the electrolyte.45 Several investigations have also been carried out into the reactivity of singlet oxygen generated during UV irradiation causing degradation of PT backbones via chain breaking and disruption to the conjugation.46,47 It is proposed that TEMPO, a known oxidizing agent for the oxidation of alcohols, may be contributing to the accelerated oxidation of the PT backbone. Recovery of the polymer from the solutions of Poly-12 and Poly-2 used for electrochemistry allowed study by both ATR-IR and UV-vis spectroscopies, which offered some insight into the nature of the film degradation. As seen in the ATR-IR spectra (Figure 5-9a), there is a distinct new stretching frequency located in the spectrum of Poly-12 after the 'polymerization' (black) that is not present before (green) at 1725 cm-1. In Figure 5-9b, comparing the recovered sample of Poly-12 (black) to Poly-2 (red), it can clearly be observed that Poly-2 is not experiencing the same degradation as the 1725 cm-1 band is not present.  178 20 40 60 80 100    b) 3500 3000 2500 2000 1500 1000 500 20 40 60 80 100  Wavenumber (cm-1)   %  Tr a n sm is si o n a)  Figure 5-9. ATR-IR spectra of (a) Poly-12 before (black) and after (green) isolation from the CV solution and (b) Poly-12 (black) and Poly-2 (red) isolated from the polymerization reaction.  The stretching frequency located at 1725 cm-1 is in the characteristic range of a carbonyl stretch (νC=O; 1700-1800 cm-1) and strongly suggests oxidation of the polymer backbone. There are several possible mechanisms that could lead to the formation of a carbonyl group within a PT backbone.46,48,49 The polymer backbone may be susceptible to hydrogen abstraction from the TEMPO, and in the presence of oxygen the polymer backbone is oxidized. Scheme 5-4 outlines a potential mechanism for the formation of carbonyl groups leading to chain scission and reduced conjugation. UV-vis spectroscopy  179 also displayed a blue shift in the maximum absorbance (436 to 430 nm), directly related to a reduction in pi-conjugation along the polymer backbone. Scheme 5-4 S S S R R R H  abstraction Chain Scission n O2 S S R R S S S R R R nS S R R S S S R R R nS S R R O S S S R R R n S S R R O m 75 76 77 78 79   Despite the lack of conductivity available from the polymer backbone, the TEMPO groups should still have demonstrated some charging behaviour. It is possible that as the conductivity of the polymer is reduced, the TEMPO groups farthest from the electrode are rendered inaccessible due to a lack of conjugation throughout the polymer. This compounds the effect of the disrupted conjugation, contributing to the disappointing measured specific charge of Poly-12.   180 5.4 Conclusions A polymer prepared via GRIM polymerization was functionalized with the stable free radical TEMPO. This new material was anticipated to display improved charging and discharging capabilities for applications towards organic based batteries. The performance of the thin films in specific capacity and charge/discharge experiments was determined to be less than optimal. Further investigations suggest that the TEMPO group may be contributing to oxidation of the backbone of Poly-12. The appearance of a new stretching frequency in the ATR-IR spectrum at 1725 cm-1 indicates the formation of a carbonyl group, a characteristic feature of oxidized PT.48,49 The disruption in conjugation caused by chain scission effectively decreases the polymers ability to conduct and store charge corroborating the low capacitance measurements of only 0.8 F g-1. It was demonstrated that the pre-formed Poly-12 and Poly-2 were deposited on electrode surfaces such as carbon during electrochemical cycling; this is a new method of depositing soluble CPs onto active electrodes. Deposition of polymers having known structures (i.e. HT regioregularity) onto electrode surfaces provides a direct correlation between structure-property relationships observed for the surface bound species. This understanding may help improve synthetic strategies towards the desired electrochemical properties of conjugated organic materials.  181 5.5 References 1. Suga, T. et al., Adv. Mater. 2009, 21, (16), 1627-1630. 2. Suga, T.; Konishi, H.; Nishide, H., Chem. Commun. 2007, (17), 1730-1732. 3. Patra, S.; Munichandraiah, N., J. Appl. Polym. Sci. 2007, 106, (2), 1160-1171. 4. Marchioni, F.; Yang, J.; Walker, W.; Wudl, F., J. Phys. Chem. B 2006, 110, (44), 22202-22206. 5. Laforgue, A.; Simon, P.; Sarrazin, C.; Fauvarque, J. F., J. Power Sources 1999, 80, (1-2), 142-148. 6. Hussain, A. M. P.; Kumar, A., J. Power Sources 2006, 161, (2), 1486-1492. 7. Laforgue, A.; Simon, P.; Fauvarque, J. F., Synth. Met. 2001, 123, (2), 311-319. 8. DeLongchamp, D. M. et al., Chem. Mater. 2005, 17, (23), 5610-5612. 9. Cui, H. N.; Teixeira, V.; Zhang, J.; Lee, H., Thin Solid Films 2006, 515, (1), 301- 306. 10. Wood, V. et al., Adv. Mater. 2009, 21, (21), 2151-2155. 11. Jahn, S. F. et al., Langmuir 2009, 25, (1), 606-610. 12. Aernouts, T. et al., Appl. Phys. Lett. 2008, 92, (3), 33306 (1-3). 13. Novák, P.; Müller, K.; Santhanam, K. S. V.; Haas, O., Chem. Rev. 1997, 97, (1), 207-281. 14. Oyaizu, K.; Nishide, H., Adv. Mater. 2009, 21, (22), 2339-2344. 15. Rozantsev, E. G.; Sholle, V. D., Synth. Int. J. Method. Synth. Org. Chem. 1971, (4), 190-202. 16. Ma, Z.; Bobbitt, J. M., J. Org. Chem. 1991, 56, (21), 6110-6114.  182 17. Gheorghe, A.; Matsuno, A.; Reiser, O., Adv. Synth. Catal. 2006, 348, (9), 1016- 1020. 18. Luo, J. T.; Pardin, C.; Lubell, W. D.; Zhu, X. X., Chem. Commun. 2007, (21), 2136-2138. 19. Wang, X. L.; Liu, R. H.; Jin, Y.; Liang, X. M., Chem. Eur. J. 2008, 14, (9), 2679- 2685. 20. Krishna, M. C. et al., J. Med. Chem. 1998, 41, (18), 3477-3492. 21. Krishna, M. C. et al., Proc. Natl. Acad. Sci. USA 1992, 89, (12), 5537-5541. 22. Búcsiová, L.; Yin, M. Z.; Chmela, Ŝ.; Habicher, W. D., J. Macromol. Sci., Pure Appl. Chem. 2008, 45, (9), 761-768. 23. Chen, X. W. et al., Macromol. Rapid Commun. 2007, 28, 1792-1797. 24. Takahashi, Y. et al., Polym. J. (Tokyo, Jpn.) 2008, 40, (8), 763-767. 25. Oyaizu, K.; Suga, T.; Yoshimura, K.; Nishide, H., Macromolecules 2008, 41, (18), 6646-6652. 26. Nishide, H. et al., Electrochim. Acta 2004, 50, (2-3), 827-831. 27. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Adv. Mater. 2008, 20, (10), 1998-2002. 28. Rozantsev, E. G.; Sholle, V. D., Synth. Int. J. Method. Synth. Org. Chem. 1971, (8), 401-414. 29. Aurich, H. G., Nitroxides. In Nitrones, nitronates and nitroxides, Patai, S., Rappoport, Z., Eds. John Wiley & Sons: Chichester, 1989; Vol. 2, pp 313-370. 30. Gheorghe, A. et al., Synlett 2006, (17), 2767-2770. 31. Morat, C.; Rassat, A., Tetrahedron 1972, 28, (3), 735-740.  183 32. Jang, K. S.; Ko, H. C.; Moon, B.; Lee, H., Synth. Met. 2005, 150, (2), 127-131. 33. Laferrière, M.; Galian, R. E.; Maurel, V.; Scaiano, J. C., Chem. Commun. 2006, (3), 257-259. 34. Banwell, C. N.; McCash, E. M., Electron Spin Resonance Spectroscopy. In Fundamentals of Molecular Spectroscopy, 4 ed.; McGraw-Hill Publishing Company: Berkshire, 1994; pp 245-256. 35. Banwell, C. N.; McCash, E. M., Infra-Red Spectroscopy. In Fundamentals of Molecular Spectroscopy, 4 ed.; McGraw-Hill Publishing Company: Berkshire, 1994; pp 55-98. 36. Inorganic Spectroscopic Methods. Brisdon, A. K., Ed. Oxford University Press: New York, 1998; p 20. 37. Whisnant, C. C.; Ferguson, S.; Chesnut, D. B., J. Phys. Chem. 1974, 78, (14), 1410-1415. 38. Electrochemical Methods: Fundamentals and Applications. 2 ed.; Bard, A. J.; Faulkner, L. R., Eds. John Wiley & Sons: Hobokin, 2001. 39. Chen, J. et al., J. Power Sources 2006, 159, (1), 708-711. 40. Passiniemi, P.; Osterholm, J. E., Synth. Met. 1987, 18, (1-3), 637-644. 41. Stenger-Smith, J. D., Prog. Polym. Sci. 1998, 23, (1), 57-79. 42. Brédas, J. L. et al., Acc. Chem. Res. 1999, 32, (3), 267-276. 43. Holzer, W. et al., Chem. Phys. 1997, 224, (2-3), 315-326. 44. Wang, J. X., Electrochim. Acta 1994, 39, (3), 417-429. 45. Wang, J. X., Electrochim. Acta 1997, 42, (16), 2545-2554. 46. Manceau, M. et al., Polym. Degrad. Stab. 2009, 94, (6), 898-907.  184 47. Manceau, M.; Rivaton, A.; Gardette, J. L., Macromol. Rapid Commun. 2008, 29, (22), 1823-1827. 48. Holdcroft, S., Macromolecules 1991, 24, (17), 4834-4838. 49. Abdou, M. S. A.; Holdcroft, S., Macromolecules 1993, 26, (11), 2954-2962.     185 CHAPTER 6 Conclusions and Future Work 6.1 General Conclusions In this thesis, a series of rr-PT derivatives were prepared, functionalized post- polymerization, and characterized by NMR spectroscopy, ATR-IR spectroscopy, solution absorption/emission spectroscopy, and CV.  The optical and electronic properties of the functionalized polymers were investigated to understand the effect of the attached pendant groups on the PT backbone. Detailed conclusions are presented and discussed within each chapter; general conclusions in reference to the initial objectives and in light of current research in the field are presented herein. The relevance of the research presented in this thesis is evident from numerous applications of CPs for organic based devices,1,2 and in particular, rrP3AT that are synthesized via GRIM conditions in order to afford a high density of HT couplings.3-15 In this research, a parent PT copolymer was synthesized via GRIM polymerization conditions, which reliably and efficiently generated a regioregular polymer with extended conjugation related to the ordered structure of the backbone. Organic electronics are developed and improved through our understanding of the structure-property relationships that extend to the bulk properties of the overall system. Generation of a diverse library of functional polymers, each with identical average chain length, polydispersity, and backbone structure is beneficial to build and expand this knowledge. Post-polymerization modification of a single reactive precursor is a useful method towards this goal.16 The Huisgen 1,3-dipolar cycloaddition reaction was used in this study to successfully attach several structurally dissimilar pendant groups to a  186 common parent PT precursor, reinforcing the utility of this reaction for post- polymerization modifications. The choice of pendant groups studied in this thesis was made based on the desire to prepare materials with in-situ tuneable properties. The ability for a material to interconvert between two distinguishable states is especially desirable when the ability to reach both states is brought about through an environmental stimulus such as light or electrical current.17-20 This thesis describes the attachment of two pendant groups that display different states upon stimulation with photons or electrons, which in turn may influence and modify the properties of the bulk polymer. In the study of DTE functionalized PT, the ring opening/closing reaction of the DTE reversibly quenched the fluorescence of the conjugated backbone.21 The significance of this finding was the amplified nature with which the photo-induced ring closing reaction quenched the polymer fluorescence. Amplified fluorescent polymers are particularly interesting for the sensitivity they exhibit upon interaction with trace amounts of analyte.22,23 Modification of the DTE backbone to incorporate gated photochromic reactivity, and thus access on-off sensor applications, is discussed vide infra. In the study of TEMPO functionalized PT, the anticipated high charge storage capability of the material was not achieved. Instead, the system was observed to physically degrade during CV studies. The TEMPO pendant group is a known oxidant for conversion of alcohols to aldehydes and ketones24-29 and the TEMPO group was contributing to oxidation of the PT backbone. Alternatively, it was determined that the PT backbone could be electrodeposited onto a carbon paper electrode. This facilitates a route to deposit thin polymer films on various conductive substrates with predefined  187 molecular structure, a currently unknown process for conventional electropolymerized species. In conclusion, the work presented in this thesis has reinforced the beneficial application of post-polymerization functionalization. Click chemistry proved to be a simple and efficient method to generate a library of diverse functional rr-PT copolymers. This research has also expanded the family of rr-PT with a variety of functional pendant groups that can be used to further modify polymer properties in-situ. Additionally, the materials prepared in this work, demonstrate promising functionality for further development towards novel organic electronic applications. 6.2 Suggestions for Future Work There are several potential new areas of study stemming from these results. In connection with the attempts to generate a conductive thin film from TEMPO functionalized PT, it may be interesting to first generate the polymer film and subsequently attach the TEMPO group. This may be achieved through several approaches. The first approach would be to electropolymerize the azide functionalized terthiophene (70) onto an electrode. The electropolymerization of terthiophene derivatives is generally easier to accomplish than polymerization of the monomer species due to a lower oxidation potential. As well, the azide group has been shown to withstand the experimental conditions of an electrochemical polymerization and would be available for subsequent Click modifications with TEMPO acetylene (74).30 This would, however, lead to a significant number of HH/TT couplings (Scheme 6-1), decreasing conjugation along the backbone, and consequently decreasing the conductivity and charge storage capability of the material.  188 Scheme 6-1 S N3 S C6H13 S C6H13 Electrochemical Polymerization S N3 S C6H13 S C6H13 R'S N3 S C6H13 S C6H13 S N3 S C6H13 S C6H13 R 70 80   A second approach would be to prepare a thin polymer film of the azide functionalized PT (Poly-2) via spin coating, drop casting, or via the electrochemical deposition demonstrated in Chapter 5, and perform the Click reaction on this surface. Click reactions are known to be tolerant of a large variety of solvents,31 therefore, solubilization of the film after deposition could easily be avoided with the proper solvent choice. It may also be interesting to apply a variation of the Click reaction recently demonstrated by Stoddard et al., in which they were able to direct-write coupling reactions between an acetylene and azide using a copper coated AFM tip.32 This process was carried out on an azide terminated self assembled monolayer (SAM) on a silicon surface. Such an approach would not only provide a better understanding of the density of TEMPO groups present at the surface, but should eliminate oxidation and therefore maintain the extended HT regioregularity of Poly-2. Another interesting avenue of future work would be the use of the amplified fluorescence quenching afforded by the ring closing reaction of DTE functionalized PT (Poly-4) for application in an ''On-Off'' organic sensor.17 This would require gated photochromic reactivity, a property through which the irradiation of any given wavelength of light does not induce colour changes unless an additional external  189 stimulant (heat,33 light of a different wavelength,34,35 or chemical36,37) is present. As a sensor, the DTE would have to be modified to only allow ring-closing reaction upon binding of an analyte of interest (Figure 6-1). The benefit of the amplified fluorescent quenching demonstrated by Poly-4, would be that only minimal concentrations of analyte would need to bind to result in 100% quenching and essentially turn off the polymer fluorescence. nnn UV Visible UV Visible  Figure 6-1. Schematic of a gated sensor based on DTE photoinduced ring-closing fluorescence quenching in which DTE ( ) can only undergo the ring-closing reaction upon binding of the analyte ( ).  Irie et al. have recently prepared a chemically gated DTE derivative (81, Chart 6-1) which was demonstrated to undergo typical photochromic reactions only upon esterification of the hydroxyl group.38 In the synthesis proposed below (Scheme 6-2), this DTE derivative could be modified to allow tethering to Poly-2 via the Click reaction. It should follow that upon esterification of the hydroxyl group, the allowed ring closing reaction of the DTE moiety would initiate fluorescence quenching along the polymer chain, thus acting as a On-Off sensor.  190 Chart 6-1 NO O SR S OH R R = CH3, Ph 81   Scheme 6-2 OO O Br2 OO O Br Br i) 1 eq. n-BuLi ii) 84 OO O Br SPh i) 1 eq. n-BuLi ii) 86 OO O SPh S OCH3 NO O SPh S O OH i) BBr ii) o-aminophenol iii) propargylbromide 82 83 84 85 86 87 88 SPh Br S OCH3 Br   191 An interesting application of this material would be to act as a sensor for the highly toxic fluorinated phosphonate sarin (Chart 6-2).39  It is reported that even very low concentrations can be fatal and it is estimated to be approximately 500 times more toxic than cyanide. Once heavily used as a chemical weapon this nerve agent still leaks from existing residual chemical stockpiles.40  Safety concerns associated with these leaks could benefit from such a sensor. It is proposed that upon reaction with compound 90, trace quantities of sarin would permit photo-induced ring-closing and thus quench polymer fluorescence (Scheme 6-3). Chart 6-2 P O O F 89    Scheme 6-3 P O O F S S N N N C6H13 x y n N OO S PhS O OH S S N N N C6H13 x y n N OO S PhS O O P O O 90 91   192 6.3 References 1. Friend, R. H. et al., Applications of Conducting Polymers. In Handbook of Conducting Polymers, 2 ed.; Skotheim, T. A., Elsenbaumer, R. L., Reynolds, J. R., Eds. Marcel Dekker: New York, 1998; pp 823-1073. 2. Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics. Perepichka, I. F.; Perepichka, D. F., Eds. John Wiley & Sons: Chichester, 2009; Vol. 2. 3. Han, Y. K.; Lee, Y. J.; Huang, P. C., J. Electrochem. Soc. 2009, 156, (4), K37- K43. 4. Zoombelt, A. P. et al., Thin Solid Films 2008, 516, (20), 7176-7180. 5. Zhang, Y.; Tajima, K.; Hirota, K.; Hashimoto, K., J. Am. Chem. Soc. 2008, 130, (25), 7812-7813. 6. Zhang, Q. L.; Cirpan, A.; Russell, T. P.; Emrick, T., Macromolecules 2009, 42, (4), 1079-1082. 7. Xue, C. H.; Luo, F. T.; Liu, H. Y., Macromolecules 2007, 40, 6863-6870. 8. Richard, F. et al., Macromol. Rapid Commun. 2008, 29, (11), 885-891. 9. Ouhib, F. et al., Macromolecules 2008, 41, (24), 9736-9743. 10. Ouhib, F. et al., Thin Solid Films 2008, 516, (20), 7199-7204. 11. Ouhib, F. et al., J. Polym. Sci., Part A: Polym. Chem. 2008, 46, (22), 7505-7516. 12. Miyanishi, S.; Tajima, K.; Hashimoto, K., Macromolecules 2009, 42, (5), 1610- 1618. 13. Li, Y. W. et al., J. Polym. Sci., Part A: Polym. Chem. 2008, 46, (12), 3970-3984.  193 14. Chang, Y. T.; Hsu, S. L.; Su, M. H.; Wei, K. H., Adv. Funct. Mater. 2007, 17, 3326-3331. 15. Bricaud, Q.; Cravino, A.; Leriche, P.; Roncali, J., Sol. Energy Mater. Sol. Cells 2009, 93, (9), 1624-1629. 16. Gauthier, M. A.; Gibson, M. I.; Klok, H. A., Angew. Chem. Int. Ed. 2009, 48, (1), 48-58. 17. de Silva, A. P. et al., Chem. Rev. 1997, 97, (5), 1515-1566. 18. Collin, J.-P.; Kern, J.-M.; Raehm, L.; Sauvage, J.-P., Metallo-Rotaxanes and Catenanes as Redox Switches: Towards Molecular Machines and Motors. In Molecular Switches, Feringa, B. L., Ed. Wiley-VCH GmbH: Weinheim, 2001; pp 249-280. 19. Irie, M., Photoswitchable Molecular Systems Based On Diarylethenes. In Molecular Switches, Feringa, B. L., Ed. Wiley-VCH GmbH: Weinheim, 2001; pp 37-61. 20. Lukas, A. S.; Wasielewski, M. R., Approaches to a Molecular Switch Using Photoinduced Electron and Energy Transfer. In Molecular Switches, Feringa, B. L., Ed. Wiley-VCH GmbH: Weinheim, 2001; pp 1-35. 21. Finden, J.; Kunz, T. K.; Branda, N. R.; Wolf, M. O., Adv. Mater. 2008, 20, (10), 1998-2002. 22. Adhikari, B.; Majumdar, S., Prog. Polym. Sci. 2004, 29, (7), 699-766. 23. Thomas, S. W.; Joly, G. D.; Swager, T. M., Chem. Rev. 2007, 107, (4), 1339- 1386. 24. Gheorghe, A. et al., Synlett 2006, (17), 2767-2770.  194 25. Gheorghe, A.; Matsuno, A.; Reiser, O., Adv. Synth. Catal. 2006, 348, (9), 1016- 1020. 26. Luo, J. T.; Pardin, C.; Lubell, W. D.; Zhu, X. X., Chem. Commun. 2007, (21), 2136-2138. 27. Ma, Z.; Bobbitt, J. M., J. Org. Chem. 1991, 56, (21), 6110-6114. 28. Sheldon, R. A.; Arends, I., Adv. Synth. Catal. 2004, 346, (9-10), 1051-1071. 29. Wang, X. L.; Liu, R. H.; Jin, Y.; Liang, X. M., Chem. Eur. J. 2008, 14, (9), 2679- 2685. 30. Bu, H. B. et al., Chem. Commun. 2008, (11), 1320-1322. 31. Binder, W. H.; Kluger, C., Curr. Org. Chem. 2006, 10, (14), 1791-1815. 32. Paxton, W. F.; Spruell, J. M.; Stoddart, J. F., J. Am. Chem. Soc. 2009, 131, (19), 6692-6694. 33. Irie, M.; Eriguchi, T.; Takada, T.; Uchida, K., Tetrahedron 1997, 53, (36), 12263- 12271. 34. Murakami, M. et al., J. Am. Chem. Soc. 2004, 126, (45), 14764-14772. 35. Uchida, M.; Irie, M., J. Am. Chem. Soc. 1993, 115, (14), 6442-6443. 36. Irie, M.; Miyatake, O.; Uchida, K.; Eriguchi, T., J. Am. Chem. Soc. 1994, 116, (22), 9894-9900. 37. Matsui, F. et al., Chem. 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