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The electrochemical properties of conducting polymers for energy storage applications Bremner, Glen 2014

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THE ELECTROCHEMICAL PROPERTIES OF CONDUCTING POLYMERS FOR ENERGY STORAGE APPLICATIONS  by  GLEN BREMNER B.Sc., McGill University, 2004  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemistry)    THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April 2014     © Glen Bremner 2014 i  Abstract The synthesis and characterization of oligothiophene-capped Au and Cu nanoparticles (NPs) are reported.  Homo- and co-polymer films of these NPs were prepared electrochemically and studied using cyclic voltammetry, electron microscopy, and absorption and emission spectroscopies. The Au NPs were capped by either 3'-thiol-substituted terthiophene (1) or 3'-phosphine-substituted terthiophene (2).  The electrochemical oxidation of 1-capped Au NPs (4) resulted in a polymeric film which displayed good electroactivity whereas attempted electropolymerization of 2-capped Au NPs (5) was unsuccessful.  Exposing the poly(4) films to an iodide/triiodide solution lead to etching of the Au and a decrease in the electroactivity of the polymer.  A hybrid copolymer was formed by electropolymerizing ethylenedioxythiophene in solution with 4 (PEDOT-4).  It was found that it was possible to selectively etch Au from PEDOT-4 films to yield porous PEDOT films, which were analyzed using elemental analysis methods and electron microscopy.  The films after etching showed slightly improved charging and discharging kinetics, suggestive of improved ionic diffusion in the polymer.   Cu NPs capped by 1 (7) were electrochemically oxidized to form a polymer film.  The lower oxidation potential of 7 relative to 4 allowed for the formation of crystalline regions in the polymer film, and exhibited the characteristic XRD peaks of Cu (0).  PEDOT-7 films were prepared which showed enhanced electroactivity over pure PEDOT films. ii  An azidostyrylthiophene compound (9) was synthesized and was shown to be both thermally and photochemically reactive.  PEDOT-9 copolymers were prepared and studied using cyclic voltammetry.  Irradiation of the PEDOT-9 films show improved charging / discharging kinetics due to crosslinking of the polymer film by the reactive azide substituent.        iii  Preface In all chapters, Professor Michael O. Wolf acted in a supervisory role and I have carried out all experiments.  Material in Chapter 4 will be published in the future with authors Bremner, G.R., Wolf, M.O.  I am the primary author under the supervision of Professor Michael O. Wolf.    iv  Table of Contents Abstract .................................................................................................................................... i Preface .................................................................................................................................... iii Table of Contents ................................................................................................................... iv List of Tables ......................................................................................................................... vii List of Figures ...................................................................................................................... viii List of Schemes ..................................................................................................................... xiii List of Equations .................................................................................................................. xiv List of Symbols and Abbreviations .................................................................................... xvi Acknowledgements .............................................................................................................. xxi Dedication ............................................................................................................................ xxii Chapter 1 Introduction .......................................................................................................... 1 1.1 Overview. ................................................................................................................. 1 1.2 Energy Storage Devices. ......................................................................................... 2 1.3 Conjugated Polymers. ............................................................................................. 8 v  1.4 Synthesis of Polythiophene. .................................................................................. 13 1.5 Electrochemistry of Polythiophene. ..................................................................... 17 1.6 Polythiophene-based Supercapacitors................................................................. 21 1.7 Supercapacitor Characterization Techniques. ................................................... 29 1.8 Goals and Scope of Present Study. ...................................................................... 38 Chapter 2 Oligothiophene-Gold Nanoparticle Hybrid Materials .................................... 40 2.1 Introduction. .......................................................................................................... 40 2.2 Experimental.......................................................................................................... 42 2.3 Results and Discussion. ......................................................................................... 47 2.4 Conclusions. ........................................................................................................... 68 Chapter 3 PEDOT-4 Copolymers ....................................................................................... 70 3.1 Introduction. .......................................................................................................... 70 3.2 Experimental.......................................................................................................... 71 3.3 Results and Discussion. ......................................................................................... 76 3.4 Conclusions. ......................................................................................................... 102 Chapter 4 Oligothiophene-capped Copper Nanoparticles .............................................. 104 4.1 Introduction. ........................................................................................................ 104 4.2 Experimental........................................................................................................ 105 4.3 Results and Discussion. ....................................................................................... 108 4.4 Conclusions. ......................................................................................................... 133 vi  Chapter 5 Azidothiophene Compounds for  Polymer Crosslinking .............................. 135 5.1 Introduction. ........................................................................................................ 135 5.2 Experimental........................................................................................................ 138 5.3 Results. ................................................................................................................. 143 5.4 Conclusion. ........................................................................................................... 157 Chapter 6 General Conclusions and Outlook. ................................................................. 159 6.1 General Conclusions. .......................................................................................... 159 6.2 Suggestions for future work. .............................................................................. 160 References ............................................................................................................................ 163 Appendix .............................................................................................................................. 176     vii  List of Tables Table 1.1.  Compilation of PT-based supercapacitors. .......................................................... 25 Table 2.1.  EDX and XPS results for the gold content of poly(4) before and after etching. ....................................................................................................................................... 66 Table 3.1.  EDX and XPS results for the gold content of polymer films with addition of 4 in the monomer solution. ............................................................................................ 78 Table 3.2.  Partial molar volume of anions at 25 °C.156 ......................................................... 87 Table 3.3. Parameters derived from EIS results of PEDOT and PEDOT-4 films. ................ 94 Table 4.1.  Comparison of the atomic composition of 7 and poly(7) . ................................ 124    viii  List of Figures Figure 1.1.  Ragone plot of energy storage devices.3 .............................................................. 2 Figure 1.2.  Charge storage in a capacitor. .............................................................................. 3 Figure 1.3.  Double layer capacitance at high surface area carbon. ........................................ 6 Figure 1.4.  Molecular structure of some conjugated polymers. ............................................. 9 Figure 1.5.  Thiophene monomers labeled with the a) α- and β- positions and b) numbering convention. .................................................................................................. 10 Figure 1.6.  Evolution of the energy band diagram as a function of chain length. ................ 11 Figure 1.7.  Oxidation of PT to form polaron and bipolaron charge carriers. ....................... 12 Figure 1.8.  Molecular structure of PT derivatives. ............................................................... 13 Figure 1.9.  Typical CV for PT in 0.1 M tetraethylammonium tetrafluoroborate / PC solution at 10 mV s-1.  Figure is from “Simultaneous Voltammetric and In Situ Conductivity Studies of n-Doping of Polythiophene Films with Tetraalkylammonium” by Levi et al.,76 reproduced by permission from ECS – The Electrochemical Society. ............................................................................................... 19 Figure 1.10.  Types of polymer-based supercapacitors. ........................................................ 22 Figure 1.11.  PT derivatives studied for supercapacitor applications. ................................... 24 Figure 1.12.  a) Triangular potential waveform and b) the current response as a function of the potential for CV.  The blue arrows in b) indicate the direction of the potential scan. ............................................................................................................................... 31 Figure 1.13.  a) Current and b) potential profile during galvanostatic charge/discharge experiment. .................................................................................................................... 34 Figure 1.14.  Sinusoidal pertubation in electrochemical impedance spectroscopy showing a) the DC potential component, b) the AC potential component, c) the sum of the AC and DC potentials.................................................................................. 35 Figure 1.15.  Nyquist plots for a model RC circuit in a) series and b) parallel (calculated using R = 10 Ω, C = 0.1 F, 1000 to 0.01 Hz). ............................................................... 38 Figure 2.1.  Functionalized oligothiophenes. ......................................................................... 42 Figure 2.2.  Transmission electron micrographs of a) 5 and b) 4. ......................................... 50 Figure 2.3.  TGA thermal profiles of a) 4 and b) 5. ............................................................... 51 ix  Figure 2.4. The effect of surface curvature on ligand packing on the Au NP surface and the SAM model. ............................................................................................................ 53 Figure 2.5.  CVs of K4Fe(CN)6 at a) dodecanethiol, b) 1- and c) 2- modified gold electrodes (red traces).  The black trace corresponds to the cyclic voltammogram of K4Fe(CN)6 at a bare (unmodified) gold electrode of the same area. ......................... 55 Figure 2.6.  CVs for a) 4 and b) 5 in a DCM solution containing 0.1 M [(n-Bu)4N](PF6). ....................................................................................................................................... 57 Figure 2.7.  UV-vis spectra for 4 (red trace) and poly(4) (black trace). ................................ 58 Figure 2.8.  a) HR-TEM image of poly(4), b) and c) TEM-EDX of poly(4).  The image in c) corresponds to the large red square numbered 2 in b).  The yellow colour indicates the location of Au atoms. ............................................................................... 59 Figure 2.9.  Scanning electron micrographs of poly(4) a) showing the general morphology of the film with magnified images of b) the ‘flat’ region of the film and c,d) of the cauliflower portions. ............................................................................. 61 Figure 2.10.  Films of a) Poly(6) and b) Poly(4)  before and after etching for 10 minutes. ....................................................................................................................................... 65 Figure 2.11.  CV of poly(4) before etching (blue trace) and after etching (red trace) at 25  mV s-1. ..................................................................................................................... 67 Figure 3.1.  Architecture of test polymer-based supercapacitors, composed of ITO-covered float glass (grey), polymer at both the anode and the cathode (red) and the PMMA membrane separator (blue)............................................................................... 74 Figure 3.2. TEM images of PEDOT-4 films. ........................................................................ 77 Figure 3.3.  Effect of etching time on the Au : S ratio of PEDOT-4.  The initial Au content was set at 100%, and all other values are relative to this. ................................ 79 Figure 3.4.  TEM images of PEDOT-4 films after etching for a), b) 3 minutes and c, d) 20 minutes. .................................................................................................................... 81 Figure 3.5. UV-vis absorption spectra for thin films of polymer deposited onto ITO. ......... 82 Figure 3.6.  CVs of PEDOT-modified glassy carbon electrodes at a) 10 mV s-1, b) 100 mV s-1, c) 500 mV s-1 for the wide potential regime and at d) 10 mV s-1, e) 100 mV s-1 and f) 500 mV s-1.  The blue scan and red scans represent the sample before and after etching. .................................................................................................................. 84  x  Figure 3.7.  CVs of PEDOT-4-modified glassy carbon electrodes at a) 10 mV s-1, b) 100 mV s-1, c) 500 mV s-1 for the wide potential regime and at d) 10 mV s-1, e) 100 mV s-1 and f) 500 mV s-1.  The blue scan and red scans represent the sample before and after etching. .................................................................................................................. 86 Figure 3.8.  CVs of PEDOT-4-modified glassy carbon electrodes at a) 10 mV s-1, b) 100 mV s-1, c) 500 mV s-1 for the wide potential regime and at d) 10 mV s-1, e) 100 mV s-1 and f) 500 mV s-1.  The blue scan and red scans represent the sample before and etching, respectively. ..................................................................................................... 89 Figure 3.9. Nyquist plots of EIS results for PEDOT at a,b) -1 V and at c,d) 0.5 V.  Plots b) and d) are magnified versions of a) and c), respectively, highlighting the high frequency regime. .......................................................................................................... 90 Figure 3.10. Nyquist plots of EIS results for PEDOT-4 at a,b) -1 V and at c,d) 0.5 V.  Plots b) and d) are magnified versions of a) and c), respectively, highlighting the high frequency regime. .................................................................................................. 93 Figure 3.11. Pictures of a PEDOT-4 device a) top-down and b) side-view. ......................... 95 Figure 3.12.  CVs of PEDOT-4 supercapacitors (black trace) and etched PEDOT-4 supercapacitors (red trace) at a) 1 mV s-1 b) 5 mV s-1 c) 10 mV s-1.  The plot of the current response as a function of time for the 10 mV s-1 scan rate is shown in d).. ...... 97 Figure 3.13.  Ragone plot of supercapacitors from PEDOT-4 (blue trace) and etched PEDOT-4 (red trace). .................................................................................................... 98 Figure 3.14.  TEM images of ripened 4 in the presence of excess 1 and [(n-Bu)4N]Br. ....... 99 Figure 3.15.  UV-vis absorption of ripened 4. ..................................................................... 100 Figure 3.16.  TEM images of ripened 4 in the presence of excess 1. .................................. 100 Figure 3.17. TEM images of a) large hexanethiol-capped Au NPs and b,c) PEDOT-Au NPs hybrid films showing Au NP aggregation. .......................................................... 102 Figure 4.1.  HR-TEM images of a) the insoluble and b) the soluble fractions separated during synthesis of 7.  The size distribution histograms for the c) insoluble and d) soluble fractions. ......................................................................................................... 110 Figure 4.2.  TGA thermal profiles of soluble (blue trace) and insoluble (red trace) fractions of 7................................................................................................................ 112 Figure 4.3.  UV-vis spectra of 7 before and after irradiation at 365 nm.............................. 113 Figure 4.4.  Fluorescence emission (λex = 340 nm) and excitation (λem = 440 nm) spectra for soluble 7 before and after irradiation at 340 nm for 15 mins. ............................... 114 xi  Figure 4.5.  Excitation spectra of 7 post irradiation monitored at 440 nm and 610 nm. ..... 115 Figure 4.6.  Electropolymerization of 7 by CV onto a glassy carbon electrode.  Red line designates the initial scan and blue lines are the subsequent scans. ........................... 117 Figure 4.7.  PXRD for poly(7) grown at a) 0.8 V and b) 1.2 V. .......................................... 119 Figure 4.8.  SEM images of poly(7) grown at 0.8 V.  Lines were added to highlight areas of microcrystallinity.  Part b) is a higher magnification image of the area enclosed in the box in part a). .................................................................................................... 121 Figure 4.9.  SEM images of poly(7) grown at 1.2 V.   The image in b) is a magnified version of the area enclosed in the box in a). .............................................................. 122 Figure 4.10.  EDX spectra for poly(7). ................................................................................ 123 Figure 4.11.  a) Full scan and b) Cu 2p XPS spectra of poly(7). ......................................... 126 Figure 4.12.  CVs of poly(7) in 0.1 M [(n-Bu)4N]PF6 in MeCN at a) 100 mV s-1 , b) 5 mV s-1 and c) 1 V s-1.  Plot d) is the current for each scan normalized by the sweep rate and e) is the plot of peak current against sweep rate. ........................................... 129 Figure 4.13.  TEM image of PEDOT-7 film........................................................................ 130 Figure 4.14.  CVs of PEDOT (blue trace) and PEDOT-7 (red trace) at a,b) 2 mV s-1, c,d) 10 mV s-1 and e,f) 50 mV s-1. ...................................................................................... 131 Figure 4.15.  Effect of scan rate on capacitance of PEDOT (red data points) and PEDOT-7 (blue data points). ..................................................................................................... 133 Figure 5.1. Irradiation of an assembled device. ................................................................... 143 Figure 5.2.  TGA thermal profile of 8 (blue trace) and 9 (red trace). .................................. 146 Figure 5.3.  a) UV-vis spectra of 8 and 9 in MeCN and b) UV-vis spectra of 9 with increasing photolysis time. .......................................................................................... 147 Figure 5.4.  a) Solid-state UV-vis spectra of irradiated 9 and b) UV-vis solution of dissolved irradiated 9. ................................................................................................. 149 Figure 5.5.  FT-IR spectra of 9 before (black trace) and after (red trace) irradiation. ......... 151 Figure 5.6.  CV of 9 in 0.1 M [(n-Bu)4N]PF6 DCM. ........................................................... 152 Figure 5.7.  CV of 9 with increasing amounts of BF3-OEt2 in 0.1 M [(n-Bu)4N]PF6 in MeCN. ......................................................................................................................... 153 Figure 5.8. CV of PEDOT-9 copolymer at a), b) 25 mV s-1 and c,d) 100 mV s-1. .............. 155 xii  Figure 5.9.  CVs of Type I supercapacitor devices built with PEDOT-9 devices at a) 5       mV s-1, b) 50 mV s-1, c) 100 mV s-1.  The plot of current response as a function of time for the 100 mV s-1 sweep rate is shown in d). ..................................................... 157 Figure 6.1.  Potential new azidooligomers with phenyl and thienyl groups. ....................... 162  Figure A.1. EDX spectra of a) poly(4) and b) etched poly(4). ............................................ 176 Figure A.2. XPS spectra of a) poly(4) and b) etched poly(4). ............................................. 177 Figure A.3. PXRD for 7. ...................................................................................................... 179 Figure A.4. Difference FT-IR spectrum for the irradiation of 9.  The spectrum before irradiation was subtracted from the spectrum after irradiation.  A negative ΔT indicates a loss in intensity for a particular IR stretch after irradiation. ..................... 180    xiii  List of Schemes Scheme 1.1.  Hierarchy of energy storage systems. ................................................................. 3 Scheme 1.2.  Ion migration during charging/discharging of conjugated polymer. .................. 7 Scheme 1.3.  Chemical Synthesis of PT. ............................................................................... 14 Scheme 1.4.  Oxidative polymerization of thiophene. ........................................................... 15 Scheme 1.5.  Reversible p-doping of PT. ............................................................................... 18 Scheme 1.6.  Ion intercalation during oxidation and reduction. ............................................ 21 Scheme 2.1.  Polymerization of Au NPs and etching of the Au NPs from the PT-Au NP film. ............................................................................................................................... 41 Scheme 2.2.  Syntheses of 1 and 2. ........................................................................................ 48 Scheme 2.3.  Synthesis of 4 and 5. ......................................................................................... 49 Scheme 4.1.  Synthesis of 7.................................................................................................. 109 Scheme 5.1.  Effect of doping/dedoping on volume of a polymer film before and after cross-linking. ............................................................................................................... 136 Scheme 5.2.  Thermolysis or Photolysis of an Azide........................................................... 136 Scheme 5.3. Synthesis of 4-azidobenzaldehyde................................................................... 144 Scheme 5.4.  Synthetic Pathway to 8 and 9. ........................................................................ 145 Scheme 6.1.  Formation of carbazole via thermolysis or photolysis o-azidobiphenyl......... 161 Scheme 6.2.  Synthesis of 3-azidothiophene. ....................................................................... 161    xiv  List of Equations Equation 1.1. ........................................................................................................................... 4 Equation 1.2. ........................................................................................................................... 4 Equation 1.3. ......................................................................................................................... 29 Equation 1.4. ......................................................................................................................... 31 Equation 1.5. ......................................................................................................................... 32 Equation 1.6. ......................................................................................................................... 32 Equation 1.7. ......................................................................................................................... 33 Equation 1.8. ......................................................................................................................... 33 Equation 1.9. ......................................................................................................................... 34 Equation 1.10. ....................................................................................................................... 35 Equation 1.11. ....................................................................................................................... 36 Equation 1.12. ....................................................................................................................... 36 Equation 1.13. ....................................................................................................................... 36 Equation 1.14. ....................................................................................................................... 36 Equation 1.15. ....................................................................................................................... 37 Equation 1.16. ....................................................................................................................... 37 Equation 2.1. ......................................................................................................................... 51 Equation 2.2. ......................................................................................................................... 62 Equation 2.3. ......................................................................................................................... 63 Equation 2.4. ......................................................................................................................... 63 Equation 2.5. ......................................................................................................................... 63 Equation 4.1. ....................................................................................................................... 111 Equation 4.2. ....................................................................................................................... 118  xv  Equation A.1. ....................................................................................................................... 178 Equation A.2. ....................................................................................................................... 178 Equation A.3. ....................................................................................................................... 178 Equation A.4. ....................................................................................................................... 178   xvi  List of Symbols and Abbreviations Abbreviation Description A Amperes, area AC Alternating current acac Acetylacetonato Anal. Analysis ATR Attenuated total reflectance a.u. Arbitrary units BE Binding energy bipy 2,2'-bipyridine C Capacitance Calcd Calculated CB Conduction band CE Coulombic efficiency cm Centimeter CNT Carbon nanotube CP Chemical polymerization CV Cyclic voltammogram / voltammetry D Crystallite size (PXRD) d Doublet DMS Mean Diameter DC Direct current DCM Dichloromethane dd Doublet of doublets (NMR) dppf 1,1'-bis(diphenylphosphino)ferrocene dppp 1,3-bis(diphenylphosphino)propane Ed Energy density Eg Band gap e- Electron EA Elemental analysis xvii  EC Ethylene carbonate EDOT 3,4-Ethylenedioxythiophene EDX Energy dispersive X-ray analysis EI Electron ionization EIS Electrochemical impedance Spectroscopy EP Electrochemical Polymerization EtOH Ethanol F Farad FWHM Full width at half maximum  g Gram GCE Glassy carbon electrode h Hour(s) HR-TEM  High resolution transmission electron microscopy hυ Light I Current i.e. Id est IR Infrared ITO Indium tin oxide J Magnetic coupling constant, NMR coupling constant j Imaginary unit LUMO Lowest unoccupied molecular orbital M Molarity m Mass, multiplet (NMR) M+ Molecular ion peak MeCN Acetonitrile MeOH Methanol min(s) Minutes(s) ml Millilitre(s) mmol Millimole MO Molecular orbital mV Millivolts xviii  mol Mole m/z Mass-to-charge ratio nm Nanometer NMP N-methyl-2-pyrrolidone NMR Nuclear magnetic resonance NP Nanoparticle Pd Power density PC Propylene carbonate PCPDT Poly(4H-cyclopentadithiophene) PDBuProDOT Poly[3,4-(2,2-dibutylpropylenedioxy)thiophene] PDDT1 Poly(dithieno[3,4-b:3′,4′-d]thiophene) PEDOT Poly(3,4-ethylenedioxythiophene) PFPT Poly[3-(4-fluorophenyl)thiophene] Ph Phenyl PMMA Poly(methyl methacrylate) ppm Parts per million PT Polythiophene PTFE Poly(tetrafluoroethylene) PVDF Poly(vinylidene difluoride) PXRD Powder X-ray diffraction P(Th-CNV-EDOT) Poly[1-cyano-2-(2-[3,4-ethylenedioxyl-thienyl])-1-(2-thienyl)vinylene] P(2,4)DFPT Poly[3-(2,4-difluorophenyl)thiophene)] P(3,4)DFPT Poly[3-(3,4-difluorophenyl)thiophene)] P3HT Poly(3-hexyl)thiophene P3MT Poly(3-methyl)thiophene P(3,4,5)TFPT Poly[3-(3,4,5-trifluorophenyl)thiophene)] R Universal gas constant, resistance S Siemens s Singlet (NMR), seconds SAM Self-assembled monolayer xix  SEM Scanning electron microscopy T Temperature t Triplet (NMR), time tc Charge time td Discharge time TEM Transmission electron microscopy TGA Thermogravimetric analysis THF Tetrahydrofuran TLC Thin layer chromatography TOAB Tetraoctylammonium bromide tos Tosyl UBC University of British Columbia UV Ultraviolet V Volts VDC DC potential VB Valence band vis Visible v/v Volume to volume ratio W Watt X Halogen XPS X-ray photoelectron spectroscopy Z Impedance Z' Real component of impedance Z'' Imaginary component of impedance Ǻ Ǻngstrom β FWHM of diffraction peak (PXRD) Δ Heat Δ Difference δ Chemical shift (ppm) ° Degrees ° C Degrees Celsius xx  ɛ Dielectric constant θ Diffraction angle (PXRD) λ Wavelength λ EM Emission wavelength λ EX Excitation wavelength λ max Wavelength at band maximum μ Micro ν Scan rate (CV) ɸ Phase difference (EIS)      xxi  Acknowledgements First, I’d like to thank Mike Wolf for allowing me to work in his lab and supporting my academic pursuits.  He has entertained many of my wild ideas and though they often ended in a dead end, I’ve learned so much from them.  I’d also like to thank all the Wolf group members besides whom I’ve had the pleasure to work.  I will always look back fondly over the times spent together, whether in the lab or out.  I’d also like to thank Professor Dan Bizzotto for being a conscientious reader of this thesis and for his useful criticisms and suggestions. This work could not have been completed without the assistance from the many UBC chemistry support facilities, particularly the mechanical and electronic shops.  I’m indebted to their ability to understand exactly what I was for, even if I wasn’t certain of it.     I extend many thanks to Professor John Madden from UBC chemical and electrical engineering for the use of his potentiostat and for useful discussions.  I’d also like Professor Frank Ko from UBC materials engineering, Professor Mark McLachlan from UBC chemistry and Professor Carl Michal from UBC Physics for the fruitful discussions during the Epod project meetings.  I acknowledge NSERC Canada, Epod Solar, UBC, St. Andrew’s Society of Montreal, the Pacific Century Graduate Fund, the Gladys Estella Laird Research fellowship for their financial support of my research pursuits and myself.    xxii  Dedication  A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly.  Specialization is for insects. - Robert A. Heinlein          For mom and dad.1  Chapter 1 Introduction 1.1 Overview.  From 2013 onwards, the world’s total energy consumption is projected to increase annually by 1.6% and is expected to surpass 6 × 1017 kJ by 2015.1  In order to meet these rising demands, much effort has gone into making renewable resources a viable option to petroleum-based energy.  While wind and solar energy are promising, they suffer from inconsistency and unreliability of energy production.  Storage of energy during peak production periods (sunny days for solar energy) to be meted out when production is low (nighttime or overcast days) is critical in making these renewable energy sources viable.     Strategies for storing energy can be diverse and include compressed air and pumped hydroelectric storage.   Batteries are at the forefront of energy storage because of their energy density, portability, and flexibility.  Not only are batteries important in storing energy from intermittent power sources but also for load leveling of conventional power plants.  Included in the field of electrochemical energy storage devices with batteries are capacitors and supercapacitors.  The demarcation between devices can be unclear, such as with Li ion batteries. A Ragone plot, wherein the energy density of the device is plotted the power density, aids in differentiating them based on their performance (Figure 1.1).  Batteries are generally considered to have high energy density but with diminished power density.  On the other hand, capacitors typically have low energy density paired with a very high power density.  Supercapacitors are intermediate between these two extremes, combining increased energy density with relatively high power density.2   2   Figure 1.1.  Ragone plot of energy storage devices.3  1.2 Energy Storage Devices. The differences between how batteries, supercapacitors and capacitors store energy provides insight into understanding electrochemical performance and their relative positions on the Ragone plot.  Even within these three categories, there are further subdivisions of the energy storage system in order to differentiate between them (Scheme 1.1).   3  Scheme 1.1.  Hierarchy of energy storage systems.   The simplest case is that of a capacitor where charge is stored in the separation of two oppositely-charged plates by a dielectric material (Figure 1.2).  The Leyden jar, invented in 1745, is the earliest example of a capacitor.   Figure 1.2.  Charge storage in a capacitor.  Portable Energy Storage SystemsBatteryPrimary SecondaryCapacitor SupercapacitorPseudocapacitorConjugated PolymerMetal OxideDouble Layer CapacitorHigh Surface Area Carbon4  The amount of energy stored is governed by the equation:  Equation 1.1.  𝐸 =12𝐶𝑉2   Where E is the energy, C is the capacitance and V is the voltage of the device.  The total energy stored is thus a function of the capacitance of the material as well as its operating voltage.  The operating voltage is limited by the maximum potential the dielectric can experience before there is current leakage between the plates.  The capacitance is determined from the equation:  Equation 1.2.                                      𝐶 =𝜀0𝜀𝑟𝐴𝑑                                                                                                                                                          Where εr is the relative dielectric permittivity, ε0 is the the vacuum permittivity, A is the surface area of the plates, and d is the distance between the plates.  The capacitance is typically limited by the area of the parallel plates and the typical energy density of a capacitor is low.  Because the charging of the plates does not require Faradaic electron transfer, the rates of the charging and discharging can be very fast.  The time constant for the formation of the double layer is on the order of 10-8 s.2  This explains the position of capacitors in the high power density-low energy density section of the Ragone plot (Figure 1.1). Batteries are defined as devices that transforms chemical energy into electric energy via a redox reaction.4  They consist of three main components: the cathode, which accepts electrons and is reduced during the redox reaction; the anode, which donates electrons and is oxidized during the redox reaction; and the electrolyte, which balances charges on the 5  electrodes via transfer of ions.  Because the energy is stored chemically, the power density of the battery is largely influenced by the kinetics of the redox reactions at both electrodes.  The time constant for redox reactions at the battery electrode range from 10-2 to 10-4 s, 4-6 orders of magnitude slower than double layer formation.2 Batteries are subdivided into primary and secondary batteries.  Primary batteries are incapable of being recharged because the electrodes are irreversibly consumed during the discharge process.  In contrast, secondary batteries can be recharged by applying a current in the opposite direction to the discharge current, which regenerates the material at both electrodes.4  The most prevalent examples of secondary batteries are lithium ion batteries found in modern electronics.   For batteries, redox reactions at each electrode involve one or two electrons per atom of the redox active material.  In comparison, there are only ~ 0.2 electrons stored per atom in a planar capacitor electrode.5  The longer time constant of redox reactions relative to double layer formation and the greater number of electrons stored per atom explain why batteries occupy the high energy density-low power density portion of the Ragone plot (Figure 1.1).   Supercapacitors include devices of many different types and can be further subdivided based on the mechanism of charge storage.5  Double layer capacitors, as their name suggests, store energy in a similar fashion as a capacitor.  In this case, charge separation is between the charged electrode and the counterions that form the electrochemical double layer (Figure 1.3).  A full supercapacitor device would include two such electrodes, one charged positively and the other negatively.  Most commonly, the electrodes are composed of high surface area carbon (HSAC).  The high surface area of the supercapacitor material and the small separation between the electrode and the electrochemical double layer results in improved energy density 6  of the supercapacitor, as is clear from Equation 1.1 and Equation 1.2.  As with capacitors, no Faradaic reactions are involved during the charging process and thus they can have relatively high power densities.     Several different methods of creating HSAC have been explored, from using novel carbon allotropes such as graphene sheets6 and carbon nanotubes7 to the pyrolysis of crude natural sources such as seaweed,8 fungi,9 or banana fibers.10  Compared to other supercapacitor materials, HSAC supercapacitors are relatively cheap and have excellent cycling ability (>100 000 times) and power density.  Currently, they are the only type of commercially available supercapacitor.    Figure 1.3.  Double layer capacitance at high surface area carbon.  Metal oxides and conjugated polymers are often classified as pseudocapacitor materials, though up to 10% of their capacitance can be due to double layer capacitance11  They store energy via Faradaic electron transfer, which precludes them from being classified as true capacitor materials.  However, their charging and discharging profiles mimic what is observed for capacitors and thus they are coined pseudocapacitors.2  Metal oxides store energy via a 7  Faradaic reactions between metal ions and H ions in acidic medium and are widely studied mainly due to the very high capacitive values achieved; however the best performing materials also tend to be expensive, for example RuO2.12-14   Conjugated polymers, which are the focus of this thesis, store energy via Faradaic electron transfer process.  Unlike other supercapacitors, the charging of polymer-based supercapacitors is not limited to the surface but occurs throughout the entire volume of the material.  This leads to an enhanced energy density for these supercapacitors, however, it negatively affects the power density.  The decrease in power density is a result of the time required for migration of charge-balancing counterions into the polymer (Scheme 1.2).  For example, charging of a highly compact polymer will take longer than for a porous polymer because the counterions have more difficulty penetrating and migrating through the polymer.  Conjugated polymers also have the advantage that they can be used to form flexible devices by depositing the polymers onto a flexible substrate.15, 16  Scheme 1.2.  Ion migration during charging/discharging of conjugated polymer.   8  One issue with comparing supercapacitor performance within the reported literature is the lack of convention in how certain figures of merit are reported (gravimetric vs. volumetric densities or the exclusion of weight of the binding materials in the calculations for the weight of the device).17  Thus, a direct comparison between devices is difficult at best, impossible at worst.  Furthermore, the behaviour of the polymer-based supercapacitors is strongly dependent on how the polymers were synthesized and processed. In order to understand the limitations and advantages of polymer-based supercapacitors, an overview of the preparative methods as well as the electrochemistry of conjugated polymers is presented.       1.3 Conjugated Polymers. Conjugated polymers have been the focus of many diverse fields of research ever since the discovery of conductive properties of doped polyacetylene (PA) by Heeger, McDiarmid and Shirakawa and the initial studies that followed this discovery.18-20  The family of conjugated polymers has grown substantially since that time to include, among many others, polythiophene (PT), polypyrrole (PPy), poly(p-phenylene vinylene) (PPV), polycarbazole (PCz) and polyaniline (PAni) (Figure 1.4).  The defining characteristic for these polymers is a delocalized π-electron system consisting of alternating single and double bonds or linked aromatic rings.  9   Figure 1.4.  Molecular structure of some conjugated polymers.  PT is a conjugated polymer that has attracted much attention because of its synthetic versatility, stability and its ability to be both n- and p- doped.  It consists of thiophene monomers linked through the α- or β- position (Figure 1.5a).  The electronic properties of PT with α,α-linkages are superior to those with α,β- or β,β- linkages.21, 22  This is attributed to enhanced π-orbital overlap in this configuration.  Cross-linking through the β-position and other defects disrupts the conjugation pathway of the π-system and changes the physical and electronic properties of the polymer.23   10   Figure 1.5.  Thiophene monomers labeled with the a) α- and β- positions and b) numbering convention.   The origin of the conductivity of PT can be explained by an adaptation of bandgap theory.  When going from thiophene to bithiophene to longer oligothiophenes and ultimately PT, the conjugation length of the molecules increases.  As the length of conjugation increases, the molecular π-bonding (HOMO) and antibonding (LUMO) orbitals begin to overlap into valence and conduction bands, respectively (Figure 1.6).24  The valence and conduction bands are separated by an amount of energy known as the band gap.  The size of the band gap determines whether the material is a metal (no bandgap), semiconductor (small bandgap), or an insulator (large bandgap).   11   Figure 1.6.  Evolution of the energy band diagram as a function of chain length.  Pristine PT has a small bandgap and behaves like a semiconductor.24  As was observed for polyacetylene, the conductivity of PT increases when the polymer is doped, a result of an increase in the number of charge carriers.25  For the oxidation of PT, these charge carriers take the form of polarons (radical cations) and bipolarons (dications).26  Polarons are formed by oxidation of the polymer, where electrons are removed from the valence band.  This causes a rearrangement of the polymer from a benzenoid to a quinoid structure and results in the appearance of new energy levels within the bandgap (Figure 1.7).  Further oxidation removes electrons from the interband energy level and results in bipolaron charge carriers.27  The empty energy level near the valence band can be thermally populated, which creates vacancies in the 12  valence band and accounts for the metal-like conductivities of p-doped PT.  At high doping levels, bipolarons are believed to be the primary charge carriers in PT.         Figure 1.7.  Oxidation of PT to form polaron and bipolaron charge carriers.   The synthetic versatility of PT allows for tuning of its electronic and physical properties and allows for the introduction of new functional groups (Figure 1.8).  The addition of an alkyl chain substituent at the β-position, as in poly(3-hexylthiophene) (P3HT), allows for soluble processing of the polymer and can affect molecular packing of the polymer.28, 29  Poly(ethylenedioxy thiophene) (PEDOT) has an ethylenedioxy group bridging the 3- and 4- positions on thiophene that prevents cross-linking during polymerization and lowers the bandgap.1, 30, 31 Attaching a fluorophenyl group lowers the reduction potential of the polymer 13  and stabilizes the n-doping of the polymer, as in poly(3-(4-fluorophenyl)thiophene) (PFPT).32  Fusion of two thiophene rings forces the thiophene rings into a planar form and lowers the bandgap of the polymer, as in the case of poly(4H-cyclopentadithiophene) (PCPDT) or the dithienophospholes studied by the Baumgartner group.33       Figure 1.8.  Molecular structure of PT derivatives.   1.4 Synthesis of Polythiophene. PT can be prepared in many different ways and its properties are dependent on the conditions under which the synthesis is performed.  In 1980, the group of Yamamoto34 and the group of Lin and Dudek,35 working independently, established the first synthetic routes to PT (Scheme 1.3).  In both cases, the reactions were based on Kumada coupling of aryl halides.  2,5-dibromothiophene was treated with one equivalent of Mg in THF, forming the Grignard reagent.  In the presence of a metal catalyst, the Grignard reagent self-couples to form 2-bromo-5′-magnesiobromobithiophene, which can then re-enter the catalytic cycle and form 14  PT.  Unsubstituted PT is insoluble in THF and so the Yamamoto and Lin-Dudek processes yield only low molecular weight polymer containing Mg impurities. Wudl later adapted a similar approach using 2,5-diiodothiophene and isolated the Grignard reagent prior to coupling to yield a PT film of higher purity.36     Scheme 1.3.  Chemical Synthesis of PT.   PT is also commonly synthesized from unsubstituted thiophene via chemical or electrochemical polymerization. In both cases, the mechanism for polymerization is similar and is initiated by one electron oxidation of the monomer to form a radical cation (Scheme 1.4).  For chemical polymerization, the oxidation was achieved via the addition of a Lewis 15  acid, such as FeCl3 (Sugimoto and Yoshino route).  Because electropolymerization is of primary importance to this thesis, the mechanism of polymerization will be explored further in the next section.     Scheme 1.4.  Oxidative polymerization of thiophene.   1.4.1 Electropolymerization. During electropolymerization, oxidation of thiophene occurs at the working electrode when a sufficiently positive potential is applied.21, 37  The radical cation species can couple with another radical cation in solution to form the dication dimer.  Alternatively, the radical cation could couple with a thiophene monomer to form a dimer which can undergo subsequent oxidation to form the dication species.38  Elimination of two protons rearomaticizes the species to form bithiophene, which can then re-enter the oxidation process to yield larger oligomers.  This continues until the oligomer is no longer soluble in solution and deposits onto the working electrode.39  The oxidation potential of longer oligomers is typically lower than that of shorter 16  oligomers, thus bithiophene will be preferentially oxidized over thiophene.40  This can result in a situation where the potential at which the oxidation of the monomer occurs is higher than that at which the polymer itself is stable, which is known as the ‘polythiophene paradox’.41  The polymer that is formed under these conditions is degraded and usually has sub-optimal electrochemical properties, e.g., low conductivity.  Whenever possible, the minimum possible oxidation potential should be used for electropolymerization.  Using a monomer with a lower oxidation potential, such as 2,2:5′,2′′-terthiophene, can help alleviate the issue. However, oligomers can be trapped in the polymer matrix when PT is prepared from terthiophene versus thiophene, which results in broadening as well as an increase in the potential of the anodic peak during oxidation of the polymer.42    The morphology and conductivity of the film are greatly influenced by several factors, including the monomer and electrolyte concentrations,43, 44 solvent,45, 46 and applied potential.47  Poly(3-methylthiophene) during the initial stages of electropolymerization possesses a smooth and compact morphology which later transitions to a more disordered and porous film.37  Electrochemically-prepared PT typically has the highest conductivity values over materials made with other preparation methods.   Although electropolymerization is typically performed under anodic conditions there are a limited number of reports of the cathodic deposition of PT.48  This method involves the addition of a species in solution with the monomer which produces a strong oxidant under reductive potentials.  Similarly, PPy has been deposited under cathodic potentials by the formation of a nitrosyl ion (NO+) from nitrous acid (HNO2).49          17  1.4.2 Photopolymerization. Photochemical polymerization of oligothiophenes has also been demonstrated, although the films are typically of poor quality, and yields are low.  Similar to the strategy used for cathodic deposition of PT, the photolysis of onium salts creates an oxidant in situ that can polymerize large band gap monomers.50, 51  Excitation of low band gap oligothiophenes in the presence of an electron acceptor, such as carbon tetrachloride,52-56 potassium dichromate57 or iodine,58 creates a radical cation which can then undergo typical coupling reactions. The photoexcitation of a TiO2-modified substrate, in the presence of an electron acceptor59, 60 or by applying a slight bias potential,61 can also trigger the polymerization of thiophene based molecules.  UV irradiation in the absence of an electron acceptor has also successfully given polymerized oligothiophenes.62   Intense UV irradiation of thiophene or halogenated thiophene in the vapour63 or liquid64 phase has led to the formation of PT.  This can also be accomplished by bombardment of thiophene molecules on specific substrates with X-ray or electron beams.65-67  In these cases, the polymerization is initiated by cleavage of a C-H or carbon-halogen bond.    1.5  Electrochemistry of Polythiophene. As described above, p-doping of PT results in the formation of bipolaron charge carriers and causes structural changes along the polymer backbone.  The benzenoid structure can be recovered by reducing the polymer back to its pristine undoped state (Scheme 1.5).24  This reversible doping/dedoping of the polymer is the basis for charge storage in polymer-based supercapacitors.    18  Scheme 1.5.  Reversible p-doping of PT.   Doping of polymer can be achieved via electrochemical or chemical means.  The electrochemical method allows for more control over the doping level of the polymer, as the charge passed through the polymer-modified electrode is directly related to the doping level.  Repulsion between the positive charges limits the number of charge carriers along the polymer backbone and doping levels of 33% of the theoretical maximum are typically achieved,68-70  though a doping level of up to 50% with CF3SO3- has been reported.71 A typical cyclic voltammogram exhibiting the reversible p- and n-doping for PT is shown in Figure 1.9.72  The breadth of the oxidation peak at 0.3 V is a result of PT not being a material of homogenous length but instead composed of polymer and oligomers of different lengths, each with slightly different oxidation potentials which overlap.  The reverse scan features a reduction peak at 0.1 V corresponding to dedoping of the polymer.  At approximately – 2 V, a reduction peak is observed which corresponds to n-doping of the polymer, which is reversible upon switching of the scan direction.  The amount of charge that can be stored in the n-doped form is significantly less than in the p-doped form in this case.  The small feature at the onset of the p-doping at – 0.1 V is a charge-trapping peak from incomplete reoxidation after n-doping.73  Also, the fact that there is very little current passed in the potential region between the p-doping and n-doping events is evidence of PT transitioning to a semiconducting state when undoped. It is an oversimplification to suggest that the current measured in a typical voltammogram is either capacitive or Faradaic in origin.  As the polymer becomes conductive 19  upon doping, there is a double-layer capacitive component to the current and the contribution from capacitive and Faradaic currents can be difficult to distinguish.74, 75                             Figure 1.9.  Typical CV for PT in 0.1 M tetraethylammonium tetrafluoroborate / PC solution at 10 mV s-1.  Figure is from “Simultaneous Voltammetric and In Situ Conductivity Studies of n-Doping of Polythiophene Films with Tetraalkylammonium” by Levi et al.,76 reproduced by permission from ECS – The Electrochemical Society.   1.5.1 Ion and Solvent Intercalation during Doping. During the doping process, PT undergoes structural and morphological changes.  The presence of bipolarons along the polymer strands cause interstrand repulsion and segments of the polymer transition from a benzenoid to quinoid structure.70  The polymer swells in order to accommodate the counterions to balance the charge of the dicationic bipolarons.24  These changes can have a drastic effect on the observed electrochemical behaviour of the film.  The electrochemically stimulated conformational relaxation model developed by Otero helps to correlate the effect of the morphological changes to the polymer to its electrochemical response.77, 78 20  Quartz crystal microbalance studies have matched the observed electrochemical behaviour of PT with mass changes in the film from the intercalation of solvent and counter ions.79, 80  Contradictory results abound in the literature about the roles of solvent and the ions, however.  This is likely a result of the different polymers samples having different morphologies depending on the conditions under which they were grown.   The shape of the voltammogram can be affected by the conditioning of the polymer prior to measurement.  By increasing the time of dedoping prior to the start of a cyclic voltammetry experiment the oxidation of PT is shifted to higher potentials.  This was attributed to desolvation during the dedoping process and the polymer becoming more compact with longer dedoping times making it more difficult for the counterions to penetrate the polymer.81   Reports that some areas of the polymer interact with solvent, whereas other (more dense) regions do not seem to be able to explain the variety of results seen.82, 83 For PEDOT, it has been shown that the inclusion of solvent during the p-doping process does not occur monotonously.  The onset of oxidation is paired with an initial loss of solvent.  As oxidation proceeds, solvent re-enters the films.  Desolvation of the polymer reoccurs at higher potentials.84      There have been some contradictory results about the role of ions during the intercalation process (Scheme 1.6), particularly that of the cation during p-doping.  Some results have concluded that cation intercalation does occur during oxidation, particularly at low potentials.42, 85  Other reports conclude that because the size of the cation does not influence the behaviour of the film, it is not involved in the process.79  Again, the differences between the two results seem to originate from the polymerization conditions, particularly the size of the electrolyte ions used during polymerization which can lead to trapped ions in the polymer.        21  Scheme 1.6.  Ion intercalation during oxidation and reduction.   The role of counterions and solvent must be carefully considered when examining the electrochemistry of PT.  It is also important that the preparative conditions of the polymer are considered when making comparisons as these can play a very large role in the behaviour of the film.  1.6 Polythiophene-based Supercapacitors. The reversible p- and n-doping of conjugated polymers is how polymer-based supercapacitors store charge.  Unlike their HSAC counterparts, charge is stored not just at the surface but throughout the polymer volume.  As mentioned previously, this has the advantage of improved energy density but results in diminished power density.  Also, the volume changes of the polymer during the doping process adversely affects cyclability, limiting it to 10 000 cycles86, 87 orders of magnitude less than for HSAC supercapacitors).88, 89 Rudge divided polymer-based supercapacitors into types based on the polymer at the anode and the cathode (Figure 1.10).90  Type I supercapacitors have the same p-dopeable polymer at both anode and cathode.  A typical maximum cell voltage of 1 V is achievable in this configuration.   22  Type II supercapacitors have two different polymers, both p-doped, at the anode and the cathode.  The maximum cell voltage can be increased to 1.5 V if polymers with sufficiently different oxidation potentials are selected.   Type III supercapacitors can attain a cell voltageof 3 V.  This is due to the pairing of an n-dopeable polymer at the anode with a p-dopeable polymer at the cathode.  The potential difference between the n-doping and the p-doping processes allows for a high cell potential.  Another advantage is that the polymers at both electrodes are initially in the fully doped conducting states, which allows for faster initial electron transfer and higher power densities.91-93  PT, unlike PPy or PAni, can be n-doped and this makes it attractive for all polymer supercapacitors.  The number of conjugated polymers that are stable in the n-doped form is still relatively small and the search for new low bandgap polymers is ongoing.  To avoid the need for an n-doped polymer, polymer hybrid supercapacitors can use HSAC as the anode polymer.86, 94, 95  Figure 1.10.  Types of polymer-based supercapacitors.  23  The preparative methods and performance of some representative PT-based supercapacitors are summarized in Table 1.1.  It has been sorted according to the polymer repeat unit, with the chemical structures shown in Figure 1.8 and Figure 1.11.  Some of the possible strategies to improve the n-doping ability of PT have been highlighted including: 1) increasing the conjugation length of the polymer by the addition of an aryl substituent in the β-position, 2) adding electron withdrawing groups to lower the reduction potential, and 3) fused ring systems, such as poly(dithieno[3,4-b:3′,4′-d]thiophene) (PDDT1), to lower the band gap energy.93  Combinations of these strategies may also be used such as with fluorinated phenyl substituents.94, 96  Table 1.1 includes the conditions for polymerization, whether chemical (denoted as CP) or electrochemical (denoted as EP) and the oxidant or electrolytic solution when appropriate.  Polymers which have been electrochemically synthesized can be used without any extra additives, provided they have been deposited onto an appropriate current collector. Tuning of the polymer’s properties can also be achieved by depositing the polymer onto different substrates.48, 60, 97  Deposition of the polymer directly onto carbon nanotubes has been done in order to improve the ionic conductivity of the polymer.98  For chemically polymerized polymers, typically a paste of the polymer with a binding agent and a conducting additive will be made and that paste coated onto a metallic current collector.   Details about the fabrication of the supercapacitor have been included to differentiate between wet two electrode systems where the electrodes are in solution, solid state devices formed with gel polymer electrolytes and devices where an electrolyte-infused separator has been used.   24  The performance of these supercapacitors will usually be reported according to the weight of the active material and not consider the extra weight of the additives.  The technique used to measure the performance (sometimes reported as the energy density or power density or capacitance) can differ as well.  A detailed examination of the different electrochemical techniques used for supercapacitor characterization is presented in the following section.  While the scope of this thesis does not include the use of PT in Li ion batteries, Haas et al. have written a comprehensive review on the subject.99     Figure 1.11.  PT derivatives studied for supercapacitor applications.   25  Table 1.1.  Compilation of PT-based supercapacitors. Polymer Polymer synthesis Supercapacitor Fabrication Electrolytic Solution Super-capacitor Type Performance Ref P(3,4,5)TFPT / P(3,5)DFPT Potentiostatic EP from 0.1 M monomer, 0.25 M Et4NBF4 in PC onto carbon current collector Polymer-modified carbon electrodes with gel polymer electrolyte. P(3,4,5)TFPT: anode P(3,5)DFPT: cathode Poly-acrylonitrile with 0.25 M Et4NBF4 in PC  Asymmetric Type III 27.6 Wh kg-1 100, 101 P(3,4)DFPT Galvanostatic EP from 0.1 M monomer and 0.2 M electrolyte in MeCN onto carbon paper  Polymer-modified carbon fibres with glass fibre paper separator  0.1 M Et4N imidazolium in MeCN III 25 Wh kg-1  (galvanostatic discharge at 5 mA cm-2) 102 PDBuProDOT Potentiodynamic EP from 0.1 M NaClO4, 0.01 M monomer in MeCN onto single carbon microfibres  0.1 M NaClO4 in MeCN Single electrode 62 mF cm-2   (EIS) 103 PDBuProDOT Potentiodynamic EP in 0.1 M Bu4NPF6, 10 mM monomer in MeCN onto bundled carbon microfibres  0.1 M Bu4NPF6 in MeCN Single electrode 12 mF cm-2 (EIS) 104 PEDOT CP by either FeCl3 or Fe(ClO4) in a MeCN solution containing multi-walled carbon nanotubes Pressed pellets of the hybrid material with glassy fibre separator 1 M Et4NBF4 in MeCN Type I (with hybrid PEDOT/CNT electrodes) 100 F g-1  (CV at 10 mV s-1) 95 PEDOT CP by Fe(III) p-toluenesulfonate in a n-butanol solution Wet 2-electrode supercapacitor with symmetrical PEDOT electrodes 0.1 M LiClO4 in MeCN I 4 Wh kg-1, 35 W kg-1  (galvanostatic discharge at 1 µA cm-2) 105 PEDOT CP by FeCl3 in CH3Cl Paste of polymer with acetylene black and PTFE coated onto Al grid, with Celgard separator 1 M Et4NBF4 in MeCN Hybrid with carbon anode 2 kW kg-1, 22.5 Wh kg-1  (galvanostatic discharge at 1 mA) 106 26  Table 1.1.  Compilation of PT-based supercapacitors. Polymer Polymer synthesis Supercapacitor Fabrication Electrolytic Solution Super-capacitor Type Performance Ref P(3,4)DFPT CP by FeCl3 in CH3Cl Paste of polymer with acetylene black and PTFE coated onto Al grid, with Celgard separator 1 M Et4NBF4 in MeCN Hybrid with carbon anode 1 kW kg-1, 28.5 Wh kg-1  (galvanostatic discharge at 1 mA) 106 P3MT Galvanostatic EP from 0.1 M monomer, 0.5 M Et4NBF4 in MeCN onto Pt disk electrode Paste of polymer with conducting additive and carboxy methyl cellulose, with PTFE separator 1 M Et4NBF4 in PC III 40 F g-1, 9 mAh g-1  (galvanostatic discharge at 5 mA cm-2) 94 P3MT CP by FeCl3 CHCl3 onto multiwalled carbon nanotubes Paste of polymer with with acetylene black and PTFE coated onto a Pt current collector 1 M KCl(aq) Single electrode 138 F g-1  (CV @ 20 mV s-1) 107 P3MT Galvanostatic EP from 0.1 M monomer and 0.01 M KBF4 in PC onto porous-PVDF-covered ITO Symmetrical device with PVDF separator 1.0 M LiClO4 in 1:1 PC-EC III 616 F g-1  (galvanostatic discharge at 10 µA cm-2) 108 P3MT Galvanostatic EP from 1 M monomer and 0.5 M Et4NBF4 in MeCN Paste of carboxy methyl cellulose and PTFE coated onto stainless steel, with PTFE separator 1 M Et4NBF4 in PC III 9 mAh g-1  (galvanostatic discharge at 5 mA cm-2) 86 P3MT CP by FeCl3 in CHCl3 solution onto mesoporous carbon Pellets of polymer with PTFE, and conducting additive pressed onto stainless steel, with glassy microfibre paper discs separator 2 M H2SO4 I 52 F g-1                            (for one electrode, by galvanostatic discharge at 2 mA cm-2) 109 P3MT Galvanostatic EP from 0.1 M monomer, 0.02 M Bu4NPF6 in nitrobenzene onto ITO Polymer-modified ITO electrodes separated by gel polymer electrolyte 40 % (w/w) PMMA in 1:1 (w/w) PC/EC mixture with NaClO4 I 10 mF cm-2 110 27  Table 1.1.  Compilation of PT-based supercapacitors. Polymer Polymer synthesis Supercapacitor Fabrication Electrolytic Solution Super-capacitor Type Performance Ref P3MT Galvanostatic EP from 0.1 M monomer, 0.02 M Bu4NPF6 in nitrobenzene onto ITO Polymer-modified ITO electrodes separated by gel polymer electrolyte 40 % (w/w) PMMA in 1:1 (w/w) PC/EC mixture with NaClO4 Type II (PPy anode) 12 mF cm-2 110 P3MT Galvanostatic EP from 0.1 M monomer, 0.02 M Bu4NPF6 in nitrobenzene onto ITO Polymer-modified ITO electrodes separated by gel polymer electrolyte 40 % (w/w) PMMA in 1:1 (w/w) PC/EC mixture with NaClO4 Type II (PPy cathode) 8 mF cm-2 110 P3MT CP by FeCl3 in MeCN-MeOH mixed solvent in the presence of multi-walled CNT. Paste of polymer-CNT hybrid material with activated carbon and PVDF and NMP onto Ni, with manila paper separator.  CNT is the anode 1 M LiClO4 in MeCN Hybrid with CNT anode 45 F g-1, 0.88 Wh kg-1  (galvanostatic discharge at 1 mA) 98 PDDT1 Galvanostatic EP from 0.1 M monomer, 0.02 M Et4NBF4 in MeCN onto carbon paper  1 M Et4NBF4 in PC Single electrode p-doping : 110 F g-1       n-doping: 75 F g-1                          (CV 20 mV s-1) 94 PDDT1 Galvanostatic EP from 0.015 M monomer and 1 M Et4NBF4 in MeCN onto carbon paper Polymer-modified carbon paper separated by gel polymer electrolyte 0.2 M Et4NBF4 in 6:1 PC/polyethylene oxide. III 7 Wh kg-1 and 65 W kg-1  (galvanostatic discharge at 0.25 mA cm-2) 93, 111 PFPT CP by FeCl3 in CHCl3 Paste of polymer with acetylene black and PTFE coated onto Al grid, with Celgard separator 1 M Et4NBF4 in MeCN Hybrid with carbon anode 0.8 kW kg-1, 32 Wh kg-1  (galvanostatic discharge at 1 mA) 106 PFPT CP by FeCl3 in MeCN Paste of polymer with carbon black and poly(vinylidene fluoride-co-hexafluoropropylene) onto Al foil separated by gel polymer electrolyte Poly(vinylidene fluoride-co-hexafluoropropylene)/PC/EC/Et4NBF4 (23:31:35:11 weight ratio) III 1.64 Wh kg-1, 268 W kg-1   (galvanostatic discharge at 250 µA cm-1) 32 28  Table 1.1.  Compilation of PT-based supercapacitors. Polymer Polymer synthesis Supercapacitor Fabrication Electrolytic Solution Super-capacitor Type Performance Ref PFPT Galvanostatic EP from 0.1 M monomer, 1 M Et4NBF4 in MeCN onto carbon paper  1 M Et4NBF4 in PC Single electrode p-doping: 95 F g-1     n-doping: 80  F g-1                       (CV 20 mV s-1) 94 PFPT / PT PFPT: CP by FeCl3 in CHCl3  PT: Polycondensation of 2,5-dibromothiophene in the presence of Mg and catalyzed by NiCl2 (diphenylphosphino ethane) Paste of polymer with graphite and carboxymethyl cellulose, with cellulosic separator.  PT is the cathode and PFT is the anode 1 M Et4NCF3SO3 Asymmetric Type III 110 F g-1 for PFPT anode  260 F g-1 for PT cathode  (galvanostatic discharge at 2.5 mA cm-2) 96 PT CP by FeCl3 in CHCl3 solution onto mesoporous carbon Pellets of polymer with PTFE and conducting additive pressed onto stainless steel with glassy microfibre paper discs separator 2 M H2SO4 I 66 F g-1  (for one electrode, by galvanostatic discharge at 2 mA cm-2) 109 P(Th-CNV-EDOT) CP by Cu(BF4)2 in benzonitrile Paste of  polymer with acetylene black and PTFE onto Al grid, with Celgard separator 1 M Et4NBF4 in MeCN Hybrid with carbon anode 1.2 kW kg-1, 35 Wh kg-1  (galvanostatic discharge at 1 mA) 106 29  1.7 Supercapacitor Characterization Techniques. The most common techniques used to investigate the electrochemical behaviour of supercapacitors or individual electrodes which compose a supercapacitor are cyclic voltammetry, galvanostatic charge/discharge experiments and electrochemical impedance spectroscopy.  Although similar data are generated from these three techniques, each technique has individual strengths and weaknesses and the values obtained can differ significantly.  The capacitance as measured with impedance spectroscopy is usually lower than that measured from cyclic voltammetry.112  A comprehensive understanding of how a supercapacitor material behaves requires the use of all three techniques.   Testing of an individual electrode is usually done in a three-electrode configuration, with a working, reference and counter electrodes.  In this case, the voltage is measured between the working electrode and the reference electrode. An important consideration when using the three electrode configuration is the size of the counter electrode.  A counter electrode should be several times larger than the working electrode to ensure that the measured capacitance is primarily from the working electrode.  As a simplification, the two electrodes can be thought of as two capacitors in series, with a resistor in between them due to solution resistance of the electrolyte.  The contribution of the capacitance of the working (CWE) and counter electrodes (CCE) to the total capacitance (Ctotal) can be calculated using the equation: Equation 1.3. 1𝐶𝑡𝑜𝑡𝑎𝑙=1𝐶𝑊𝐸+1𝐶𝐶𝐸 30  If CWE and CCE are of the same magnitude, then the measured capacitance will be half the value of the capacitance of the working electrode.  As CCE becomes very large its contribution decreases and the measured capacitance becomes closer to that of the working electrode.  In practice, a very large Pt mesh electrode is often used for this purpose.   Testing of the supercapacitor is done in a two electrode set-up with the anode and the cathode of the supercapacitor.  In this configuration, the cell voltage, which is the voltage difference between the anode and the cathode, is measured.  In this configuration, if the device is symmetrical, the electrodes will be of the same size.  1.7.1 Cyclic Voltammetry. In cyclic voltammetry, a triangular waveform potential is applied to the working electrode (Figure 1.12a) and the current at the working electrode is measured as a function of the applied potential (Figure 1.12b).113, 114  The potential scan rate, ν (V s-1), can be changed to examine the response of the electrode to fast or slow changes in the potential.  The faster potential scan mimics the use of a supercapacitor under high power load.  If the electrode behaves like an ideal capacitor, the current response to the potential sweep will have a square appearance with a positive current during the forward scan (increasing potential) and a negative current during the reverse scan (decreasing potential).  The ideal capacitor is composed of “ideally polarizable” metal interfaces.  The “ideally polarizable” interface is one where upon applied potential, charges flow solely to charge the interface and do not flow across the interface.83, 115  The maximum capacitance of the electrode or supercapacitor can be calculated from the maximum current during the forward scan using the equation:  31  Equation 1.4.                                      𝐶 (𝐹) =𝑖(𝐴)𝜈 (𝑉𝑠−1)   Where C is the capacitance, in Farads, i is the current in Amperes and ν is the scan rate in Vs-1.  The switching time, defined as the time to reach maximum current after the switch from forward to reverse scan, is 0 s for an ideal capacitor without resistance, as depicted as the blue trace in Figure 1.12b.  Otherwise, the switching time is determined by the RC time constant, where R is the resistance in ohms and C is the capacitance.  As the RC time constant increases, so do the deviations from the ideal rectangular shape and the time to reach the maximum current (Figure 1.12b black and red traces).  Repeated cycling of the potential can also be used to determine the lifetime of the supercapacitor and to measure how its performance degrades with use.     Figure 1.12.  a) Triangular potential waveform and b) the current response as a function of the potential for CV.  The blue arrows in b) indicate the direction of the potential scan.     32  1.7.2 Galvanostatic Charge/Discharge Experiments.   Galvanostatic charging/discharging experiments can also be performed in order to calculate capacitance, power and energy densities and the coulombic efficiency of electrodes.  A constant positive current is applied and as a result the electrode becomes charged and its potential increases.  Once a defined maximum potential has been reached, the direction of the current is reversed (Figure 1.13a).  The potential of the electrode decreases as it discharges until a set minimum limit has been reached.  At this point, the positive current is reapplied to restart the next charging cycle.  In the case of an ideal capacitor, the potential during one charge-discharge cycle takes a triangular shape (Figure 1.13b).  From the charge-discharge profile, the coulombic efficiency can be calculated from the ratio of the discharging to discharging times:  Equation 1.5.  𝐶𝐸 =𝑡𝑑𝑡𝑐× 100%   Where CE is the coulombic efficiency, td and tc are the discharging and charging times, respectively, in s.  The capacitance can also be calculated from the slope of the discharge profile using the equation:  Equation 1.6.                                      𝐶 = 𝑖∆𝑡𝑑∆𝑉   33  Where C is the capacitance in F, i is the applied current, and ΔV is the change in potential during the discharging process in V.  The energy density of the electrode is calculated from the area underneath the discharge profile:  Equation 1.7.                                       𝐸𝑑 =𝑖𝑚∫𝑉𝑑𝑡    Where Ed is the energy density (Whkg-1), m is the mass (kg), i is the current (A) and ʃ(Vdt) is the area underneath the discharge profile (Vh).  The power density can be calculated using the equation: Equation 1.8.                                      𝑃𝑑 =𝐸𝑑𝑡𝑑   Where Pd is the power density (Wkg-1)and td is the discharge time (h).  The energy density is often plotted against the power density in order to generate a Ragone plot.  By changing the applied current, the change in the energy density with the power density can be plotted.  In the ideal case, the electrode will be able to maintain the same energy density even under very high power demands (simulated by applying a large current).  Typically, the energy density will decrease with increasing power density.  This can be due to a variety of causes.  Polarization of the electrode occurs under high power demands and the ohmic IR resistance increases.  Both of which result in a drop in the voltage, which leads to a decrease in the energy density (Equation 1.7.).  For pseudocapacitor materials, depletion of the electrochemical species near 34  the electrode can occur, at which point the energy density is limited by diffusion of that species from the bulk to the electrode.5  As with the cyclic voltammetry, the charge/discharge sequence can be cycled repeatedly to test the long-term stability of the electrode.        Figure 1.13.  a) Current and b) potential profile during galvanostatic charge/discharge experiment.  1.7.3 Electrochemical Impedance Spectroscopy.   Electrochemical impedance spectroscopy is a powerful technique to probe the behaviour of electrodes under different power demands.  In this technique a small AC potential is superimposed over a DC potential (Figure 1.14) and the current response to the AC potential is measured.116  The applied potential becomes a function of time:    Equation 1.9.                                      𝑉(𝑡) = 𝑉𝐷𝐶 + 𝛥𝑉 cos(𝜔𝑡)   a) b) 35  Where VDC is the DC potential (V), ΔV is the magnitude of the AC potential (V), ω is the angular frequency of the AC potential (rads-1) and t is the time (s).      Figure 1.14.  Sinusoidal pertubation in electrochemical impedance spectroscopy showing a) the DC potential component, b) the AC potential component, c) the sum of the AC and DC potentials.  The current is governed by the equation:  Equation 1.10.                                      𝐼(𝑡) =  𝛥𝑉│𝑍│cos(𝜔𝑡 + 𝛷)   Where the I(t) is the current (A), │Z│ is the impedance (Ω) and Φ is the phase difference between the potential wave and the current sine wave.  If an electrode behaves purely resistively, Φ = 0o.  For purely capacitive processes, Φ = 90o.  The impedance, │Z│, has two components:  a) b) c) 36  Equation 1.11.                                      │𝑍│ = √(𝑍′)2 + (𝑗𝑍′′)2   Where Z is the impedance, Z′ and Z′′ are the real and imaginary impedances respectively, all in Ω.  The real impedance, Z′, corresponds to the in-phase current response.  The imaginary impedance, Z′′, corresponds to the out-of-phase current response.  The impedance response of a system is often modeled using electrical circuits, in the simplest cases with resistors, capacitors and inductors.  The impedance of a pure resistor is:  Equation 1.12. 𝑍𝑟𝑒𝑠𝑖𝑠𝑡𝑜𝑟 = 𝑅 The impedance of a capacitor is:  Equation 1.13. 𝑍𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑜𝑟 =1𝑗𝜔𝐶 The impedance of an inductor is:  Equation 1.14. 𝑍𝑖𝑛𝑑𝑢𝑐𝑡𝑜𝑟 = 𝑗𝜔𝐿   Combinations of these electrical components in series and/or in parallel are used to model the behaviour of the experimental system.  For two elements in series, Z1 and Z2, the total impedance is the sum of the impedance of the two components:  37  Equation 1.15. 𝑍 = 𝑍1 + 𝑍2 Whereas for two elements in parallel, the total impedance is:  Equation 1.16. 1𝑍=1𝑍1+1𝑍2   The impedance of a circuit that includes several elements in series and parallel can be derived from Equation 1.15 and Equation 1.16.    The frequency of the AC potential, ω, is often varied, and the impedance contribution of the different components will change based on Equation 1.12 - Equation 1.14.  For example, the impedance of the resistor is independent of frequency (Equation 1.12) whereas the impedance of a capacitor has an inverse frequency dependence (Equation 1.13).  The purpose of varying the frequency isto probe the current response of the system in different time domains.  In order to visualize impedance spectroscopy data, a Nyquist plot can be generated by plotting Z′′ against Z′ at all the measured frequencies.  The shape of the plot provides insight into the behaviour of the system in the different time regimes.  For a simple circuit with a resistor in series with a capacitor, the Nyquist plot resembles Figure 1.15a.  Each data point represents the impedance at a particular frequency.  The real impedance, Z', for this circuit is independent of frequency.  Where the plot intercepts the x-axis yields a true resistance value.  38  The Nyquist plot for a resistor in parallel with a capacitor is shown in Figure 1.15b.  In this case, both Z' and Z'' are frequency dependent.              Figure 1.15.  Nyquist plots for a model RC circuit in a) series and b) parallel (calculated using R = 10 Ω, C = 0.1 F, 1000 to 0.01 Hz).  1.8 Goals and Scope of Present Study. The overarching theme of this thesis is the improvement of particular electrochemical traits of PT with an eye towards their potential use in an electrochemical supercapacitor.  This was approached in different ways depending on the parameter that was being explored.  Oligothiophene-capped metal nanoparticles (Au and Cu) were electrodeposited to form metal NP-polymer hybrid films which exhibited reversible charging and discharging (chapters 2 and 4).  The Au nanoparticles were used as a sacrificial in a PEDOT to increase the porosity of the polymer and enhance ion diffusion (chapter 3).  PEDOT was co-electropolymerized with an a) b) ω  39  azide containing monomer in order to see if cross-linking of the polymer could improve the ionic conductivity of the polymer, particularly in the dense undoped state (chapter 5).     40  Chapter 2 Oligothiophene-Gold Nanoparticle Hybrid Materials 2.1 Introduction. A polymer-based supercapacitor stores energy by injecting charge from the current collector into the polymer strands.  During this process, counterions from the electrolyte must diffuse from the electrolytic solution into the polymer in order to balance the charge.  This becomes a significant issue during periods of high power demands when slow ion diffusion can limit the energy density of the material.  The ion diffusion problem has been addressed in the past by either depositing a very thin layer of the polymer onto a high surface area substrate, such as a carbon nanotube film97 or into a porous alumina template,117 or by enhancing the native porosity of the films.118  The latter solution typically has involved adding a porogen, such as an immiscible volatile solvent, during the polymerization process which creates micron-sized pores in the polymer.119   The approach described in this chapter is polymerization of the conducting polymer in the presence of a sacrificial template.  The template is a material that can be removed post-polymerization, creating template-sized pores in the conducting polymer.  A homogenous distribution of pores throughout the polymer is ideal and so control of the interaction between the polymer and the sacrificial template is important.  If, for example, there is a stronger interaction between the template groups than between template and polymer, this could lead to agglomeration of the template in the polymer.  After removal of the template, there would be areas of polymer of very high and very low porosities.  The areas of low porosity would exhibit minimal improvement in ion diffusion.  Gold nanoparticles (Au NPs) capped with electropolymerizable oligothiophene ligands are well-suited for the role as a sacrificial 41  template.  The Au NP core acts as the template and will be evenly distributed upon polymerization of the oligothiophene capping group.  This approach to forming Au NP-polymer hybrid materials has been used previously to study the synergy between the Au NP and the conducting polymers on a variety of electronic and photophysical properties.120, 121   The use of Au NPs as sacrificial templates has also been explored previously but only with non-conducting polymers.  In that case, selective etching of the nanoparticles resulted in nm-sized pores in the polymer, of approximately the same shape as the nanoparticles.122  In this chapter, this concept has been extended to conducting polymers where the Au NPs are electropolymerized leading to a nanoparticle-embedded polymer film.  Removal of the Au NPs from the PT-Au NP film should create pores in the polymer, through which ions can freely diffuse through the polymer (Scheme 2.1).     Scheme 2.1.  Polymerization of Au NPs and etching of the Au NPs from the PT-Au NP film.   In this chapter, the synthesis of a new thiol-oligothiophene capping ligand (1 in Figure 2.1).  Two batches of Au NPs were synthesized capped by either the thiol-oligothiophene or the phosphino-oligothiophene (2 in Figure 2.1) and the difference in properties between these 42  particles is elucidated.  The electrochemical behaviour of the Au NP-PT films before and after etching is explored, with respect to their potential application in polymer-based supercapacitors.  In order to highlight the importance of functionalizing the ligand in the 3'-position, the effect of etching on polymer films of Au NPs capped by an oligothiophene functionalized at the 2-position (3 in Figure 2.1) was also explored.    Figure 2.1.  Functionalized oligothiophenes.  2.2 Experimental. 2.2.1 General.  Chemicals were purchased from Aldrich, except for HAuCl4.3H2O which was purchased from Strem Chemicals.  All chemicals were used as received except chlorodiphenylphosphine which was distilled prior to use and [(n-Bu)4N]PF6, which was recrystallized three times from hot EtOH and dried in vacuo at 100 °C for 5 days.  Au NPs capped by 3 with an average molecular formula of Au146(3)56 were obtained from former Wolf group colleague Dr. B.C. Sih (6).  Indium-tin oxide (ITO) coated unpolished float glass (Rs = 4 – 8 Ω) was purchased from Delta Technologies.  Glassy carbon working electrodes (2 mm diameter) and Ag/Ag+ non-aqueous reference electrodes were purchased from BASi.  A 0.1 M [(n-Bu)4N]PF6, 0.01 M    1 2 3 43  AgNO3 MeCN solution was used in the non-aqueous reference electrode.  All reactions were performed in an inert N2 (99.0 %) atmosphere using standard Schlenk technique with dry solvents, unless otherwise stated.  3′-bromo-2,2′:5′,2′′-terthiophene was prepared following its literature synthetic procedure.123  3′-diphenylphosphino-2,2′:5′,2′′-terthiophene (2) was prepared following its literature synthetic procedure.124  1H NMR and 31P NMR were collected on either a Bruker AV-300 or AV-400 spectrometer.  1H NMR spectra were referenced to residual solvent and 31P NMR spectra referenced to external 85% H3PO4.   Electropolymerization and cyclic voltammetry were performed using a Brinkmann PGSTAT12 Autolab potentiostat.  TEM was performed using a Hitachi H7600 Electron Microscope operating at 100 kV.  Imaging of individual Au NPs was achieved by dropcasting from a CH2Cl2 solution onto 300-mesh carbon-coated copper grids.  The average diameter was calculated from a sample of 100 nanoparticles distributed over a minimum of 4 TEM micrographs and is reported with an error of one standard deviation. TEM imaging of polymer films was achieved by direct electropolymerization onto the 300-mesh carbon-coated copper grids.  SEM and EDX spectroscopy was performed using a Hitachi S-3000N electron microscope on polymer samples deposited on ITO. The polymer films were oxidized to 1V prior to acquiring their SEM images in order to increase the conductivity of the films.  Thermogravimetric analyses (TGA) were performed using a Perkin-Elmer Pyris 6 TGA on 5 mg (± 1mg) samples with a temperature ramp of at 10 °C/min from 30 °C to 900 °C.        44  2.2.2 Synthesis. 3′-Thio-2,2′:5′,2′′-terthiophene (1).  The synthesis of 3′-thio-2,2′:5′,2′′-terthiophene (1) was based on a previously reported synthesis of a related thiol-containing oligothiophene.125   A solution of 3′-bromo-2,2′:5′,2′′-terthiophene (4.05 g, 12.3 mmol) in dry ether (100 ml) was cooled to -78 °C and stirred under N2.  1.6 M n-butyllithium (10.0 ml, 16.0 mmol) was added dropwise and the solution was allowed to stir for one hour at –78 °C.  S8 (0.799 g, 3.11 mmol) was added at once and the solution was allowed to warm to room temperature and stirred for 16 hrs.  An aqueous 2 M NaOH solution (20 ml) was added to the reaction mixture and stirred for 2 hrs.  The reaction was then quenched by addition of 1 M HCl (50 ml) and the organic layer extracted with ether.  The organic layer was subsequently washed three times with 50 ml of deionized H2O and dried over anhydrous MgSO4.  The product was purified on a silica column using a 7/3 (v/v) hexanes : acetone solvent.  Sonication of the resulting brown-red oil in a minimal amount of acetone yielded a solid yellow precipitate, which was collected via vacuum filtration to yield 0.951 g (27.6 %).  1H NMR (300 MHz, CDCl3): δ, 7.03 (dd, J = 5.3, 3.9 Hz, 1H), 7.09 (dd, J = 5.0, 3.9 Hz, 1H), 7.21 (s, 1 H), 7.27 (dd, J = 3.9, 0.9 Hz, 1H), 7.33 (dd, J = 3.9, 1.4 Hz, 1H), 7.48 (ddd, J = 5.1, 2.9, 1.1, 2 H).  HRMS (EI) Calcd for C12H8S4 (m/z): 279.9509; Found: 280.0110. Anal. C12H8S4 requires C, 51.39; H, 2.88; N, 0 %. Found C, 51.68; H, 2.94; N, 0.10 %.         3′-Thio-2,2′:5′,2′′-terthiophene capped Au NPs (4).  The gold nanoparticles were prepared according to a modified Brust-Schiffrin synthesis.126  To a N2-sparged solution of 1/1 (v/v) toluene : water (60 ml), HAuCl4.3H2O 45  (0.4109 g, 1.022 mmol) was added.  Tetraoctylammonium bromide (0.6023 g, 1.102 mmol was added to the mixture.  Once the gold salt was transferred to the organic phase, as determined by the colour change in the toluene layer from clear to red, 1 (0.621 g, 2.22 mmol) was added.  The solution was stirred for 1 hour at which point 10 ml of a freshly-prepared 1M aqueous solution of sodium borohydride was added at once. A gas immediately evolved along with a colour change from yellow to brown followed by a change to black.  The solution was allowed to stir for 4 hrs at room temperature and the organic layer was then extracted and washed repeatedly with deionized water to remove any excess tetraoctylammonium bromide.  The solvent volume was decreased by heating under reduced pressure and the nanoparticles were precipitated from solution by addition of hexanes.  The nanoparticles were filtered, redissolved in a minimum amount of DCM, and subsequently precipitated out in hexanes and refiltered.  This process was repeated until the filtrate was clear, indicating the complete removal of any unbound oligothiophene.  The black solid (123 mg) was removed from the filter.  The lack of unbound oligothiophene was further confirmed via 1H NMR spectroscopy of the gold nanoparticles which showed only broad peaks in the aromatic region corresponding to bound oligothiophene.    3′-Phosphino-2,2′:5′,2′′-terthiophene capped Au NPs (5) The material was synthesized according to the same procedure used for 4 except that 2 was used instead of 1.  A yield of 98 mg was obtained.  The lack of unbound oligothiophene was confirmed via 1H NMR spectroscopy of the Au NP which showed only broad peaks in the aromatic region corresponding to bound oligothiophene.  No peaks were observed in the 31P NMR spectrum of 5. 46   2.2.3 Self-Assembled Monolayers.  Self-assembled monolayers (SAMs) were prepared by immersing a 1 mm diameter gold button electrode in a 10 mM 1/1 (v/v) EtOH : DCM solution of either 1, 2, or dodecanethiol for 12 hours.  Prior to use, the gold button electrodes had been polished using fine alumina paste, rinsed in sequentially in deionized water and acetone, and dried at 80 °C.  The SAMs were rinsed in DCM three times.  Testing of the packing density of the SAMs was done in a three electrode electrochemical set-up.  The SAM-modified gold electrode functioned as the working electrode, with a platinum mesh counter electrode and a Ag wire reference electrode.  All three electrodes were tested in a 2 mM K4Fe(CN)6 / 0.1 M KCl aqueous solution.         2.2.4 Cyclic Voltammetry of 4 and 5. The cyclic voltammograms of 4 and 5 were collected from 10 ml of a 0.1 M [(n-Bu)4N](PF6) DCM solution to which 10 mg of the Au NPs had been added using either a 1 mm diameter Pt button, 3 mm diameter glassy carbon, or an ITO slide as the working electrode.  Ag wire and Pt mesh were used as the pseudoreference and counter electrodes, respectively.  If material deposited, the working electrode was rinsed three times with DCM and left to dry in a laboratory atmosphere.    47  2.2.5 Testing of the Polymer-modified Electrodes. Electrochemical testing of the polymer-modified samples was performed in a MeCN solution containing 0.1 M [(n-Bu)4N](PF6) with a platinum mesh counter electrode and a Ag/Ag+ (0.01 M) reference electrode, unless otherwise stated.     2.2.6 Etching of the Au NPs. Etching was performed by immersing the polymer-modified electrode in a DCM solution containing 0.05 M [(n-Bu)4N]I and 5mM I2.  Unless otherwise stated, the samples were exposed to the etchant for three minutes.  The polymer sample was then dedoped electrochemically by applying a -1 V potential for five minutes in a MeCN solution containing 0.1 M [(n-Bu)4N](PF6).  After dedoping, the sample was rinsed with DCM three times.  The samples were left to dry in a laboratory atmosphere.  2.3 Results and Discussion. 2.3.1 Synthesis. In previous work on oligothiophene-capped Au NPs, the oligothiophene was bound to the Au NP surface via functionalization at the α- position of a terminal thiophene group.120  In the case of 3, the oligothiophene is functionalized by a diphenylphosphino group at one α- position (Figure 2.1).  Because of the location of the functionalization, only one α- position on 3 remains available for polymerization.  This limits the extent of polymerization to dimers of 48  3.  When 3-functionalized Au NPs (6) are electropolymerized, the resulting polymer film is composed of dimers of 3 linked by Au NPs.  However, if the Au NPs are removed via etching, the remaining dimers of 3 do not form a stable film.  Because of the need for the polymer film to remain intact post-etching, terthiophenes derivatized at the 3'- position with either a thiol (1) or phosphine (2) functionality were used to cap the Au NPs.  Both terminal α- positions are available for polymerization in 1 and 2, which allows for the formation of much longer oligomer chains. The syntheses of 1 and 2 were accomplished via a lithium halogen exchange reaction followed by quenching with either elemental sulfur or chlorodiphenylphosphine, respectively (Scheme 2.2).  The reaction is performed in dry ether and at low temperatures in order to avoid the halogen dance reaction which can occur in THF, as this can lead to rearrangement of the substituted species.127    Scheme 2.2.  Syntheses of 1 and 2.  The syntheses of 4 and 5 followed a modified Brust-Schiffrin synthesis.  Both thiols and phosphines are well known to form strong interactions with Au atoms and are common functional groups used to cap Au NPs. Thiols generally form more robust monolayers on Au surfaces than phosphines.128, 129 49  Scheme 2.3.  Synthesis of 4 and 5.    Both thiol- and phosphine-capped Au NPs were isolated after purification as black powders.  The nanoparticles were soluble in DCM, toluene and CHCl3 and insoluble in PC, MeCN and hexanes.     2.3.2 Characterization of Au NPs 4 and 5. Transmission electron micrographs confirm the formation of both types of Au NPs (Figure 2.2).  Sizing of the particles using ImageJ software determined that they are of similar diameters, 1.8 ± 0.6 nm and 2.1 ± 0.8 nm for 4 and 5, respectively.   50   Figure 2.2.  Transmission electron micrographs of a) 5 and b) 4.   TGA of the Au NPs shows that 4 and 5 consist of 35% and 30% organic material by weight, respectively (Figure 2.3).  The desorption process for nanoparticles capped with either ligand occurred in at least three distinct steps: at approximately 220, 250 and 500 °C.  Attempts at identifying the species that desorbed at each step using TGA-MS were unsuccessful.  A two-step desorption process has been observed in nanoparticles capped by 3-(10-mercaptodecyl)thiophene, though the authors did not offer a possible explanation for this observation.130  One possibility is that ligands bound to different sites on the gold nanoparticles (vertices, edges, or terraces) have different desorption temperatures because of their different strengths of absorption.  a) 20 nm b) 51   Figure 2.3.  TGA thermal profiles of a) 4 and b) 5.  Though Au NPs do not have the well-defined atomic structure of a small molecule, their average molecular formulae can be calculated from a combination of TEM and TGA results.  The average number of Au atoms, NAu, per Au NP can be calculated from the core diameter, DMS, as measured from the TEM micrographs using Equation 2.1.131 Equation 2.1.                                         33 6/59 MSAu DnmN     Equation 2.1 is derived by multiplying the density of gold atoms in a bulk fcc structure (59 atoms nm-3) by the volume of the Au NP, under the assumption that the NP is a perfect sphere,  Using Equation 2.1, and the weight percent of organic material of the Au NPs as measured using TGA (Figure 2.3), the average molecular formulae are calculated to be Au101(2)20 and Au101(1)36.  This is a fairly significant difference in the number of capping ligands surrounding the Au core.  In a previous example with 3-capped Au NPs,120 where the terthiophene was a) b) 52  substituted at the 2- instead of the 3′-position, the Au NPs had an average molecular formula of Au146(3)56.120  In order to compare the packing densities, the number of ligands per surface area unit as calculated using Equation 2.2 and the assumption that the nanoparticles are perfect spheres:  Equation 2.2.                                      𝑃𝑎𝑐𝑘𝑖𝑛𝑔 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 (𝑛𝑚−2) =𝑁𝑙𝑖𝑔𝑎𝑛𝑑𝑠4𝜋𝑟2    The calculated ligand packing densities were 3.7 and 1.6 ligands/nm2 for the nanoparticles capped by 3 and 2, respectively.  The calculated packing density for 4 was 2.9 ligands/nm2.  The difference in capping density suggests that the terthiophenes substituted at the 3′ position are more sterically hindered around the Au NPs than those substituted at the 2-position, and cannot pack efficiently around the Au NP.  2.3.3 Self-assembled Monolayers of 1 and 2 on Gold.   In order to further understand the observed difference in the packing densities of the Au NPs, SAMs of 1 and 2 were formed on the surface of a gold dot electrode.  This approach involves measurement of the packing efficiency on a 2-dimensional surface rather than on a 3-dimensional Au NP, allowing differences between the packing densities of the two capping ligands to be studied more readily.  The 2-dimensional surface is not a perfect model for the 3-dimensional Au NPs as it does not take into consideration the different surface sites on the Au NPs (edges, vertices, and terraces) as well as the curvature of the Au NP (Figure 2.4).  53  These factors should allow for more ligands to be absorbed onto the Au NP than a flat surface.  However, the 2-D SAM model allows for a relative packing density comparison between the two ligands and eliminates the variables from the Au NP synthesis (NP diameter and dispersity) that can convolute the results.   Figure 2.4. The effect of surface curvature on ligand packing on the Au NP surface and the SAM model.  The surface packing densities of the SAMs were probed electrochemically in an aqueous solution of K4Fe(CN)6.132   If a dense monolayer of the capping ligand is formed on the electrode, the K4Fe(CN)6 will be blocked from approaching the electrode and very little current will be observed from the Fe(II)/Fe(III) redox couple.  Conversely, should the terthiophene molecules not pack efficiently as a monolayer, then K4Fe(CN)6 will be able to approach the electrode and a strong redox current will be observed.  A dodecanethiol SAM was also formed under identical conditions for comparison purposes.  Dodecanethiol is known to form dense monolayers on gold and acts as an insulating barrier to electron transfer.133     The results from the ferricyanide blocking test are shown in Figure 2.5.  The dodecanethiol SAM (Figure 2.5a) shows the expected behaviour, with very little current 3-D Au NP surface 2-D Au SAM model 54  observed from the ferricyanide redox couple when the SAM is formed (red trace) as compared to the same gold electrode without a SAM present (black trace).  This is consistent with the formation of a dense monolayer which prevents the ferricyanide from approaching the electrode.  Similar behaviour is observed for the gold electrode modified with the SAM of 1 (Figure 2.5b), with very little current from the ferricyanide redox couple.  These results contrast with the 2-modified gold electrode (Figure 2.5c), where only a slight reduction in the ferricyanide redox current is observed relative to a bare gold surface.   These results are consistent with 1 being able to pack more efficiently than 2 on Au surfaces, both as a SAM on a flat gold surface or on the Au NPs.  The extra steric hindrance from the phenyl groups on the phosphine as well as the relatively weaker Au-P bond could be the cause for the diminished packing density of 2 versus 1 on the flat gold surface.  This is consistent with previous work where it was found that fewer capping ligands were required to cap Au NPs when the ligand contained a phosphine group than with the corresponding thiolate.134 55   Figure 2.5.  CVs of K4Fe(CN)6 at a) dodecanethiol, b) 1- and c) 2- modified gold electrodes (red traces).  The black trace corresponds to the cyclic voltammogram of K4Fe(CN)6 at a bare (unmodified) gold electrode of the same area.  2.3.4 Electropolymerization of 4 and 5.     The electropolymerization of the Au NPs to make a Au NP-polymer hybrid material is the first step towards the desired porous PT.  Cyclic voltammograms of both Au NPs are presented in Figure 2.6.  For 4, as the potential is swept anodically, an increase in current is observed around 1.6 V indicative of oxidation of the monomeric terthiophene groups a) b) c) 56  surrounding the gold nanoparticles (Figure 2.6a).  Upon successive scans, a redox wave forms at 1.3 V attributed to the reversible oxidation and reduction of longer oligomers formed during polymerization.  The current also increases with subsequent scans, again indicative of the formation of an electroactive polymer film.135  The formation of a polymer film is further confirmed by visually inspecting the electrode at the end of the experiment, which revealed the presence of a black insoluble material on the electrode surface.  The high oxidation potential of the monomer 4 is problematic because the PT as it is being formed is prone to oxidative degradation at these potentials.  This phenomenon, often referred to as the ‘polythiophene paradox’ is well known for monomers with high oxidation potentials.41    Unlike 4, 5 did not electropolymerize (Figure 2.6b).  Successive scans do not result in an increase in current expected for electropolymerization and no polymer film is visually observed on the electrodes.  The Au NPs’ lower surface coverage may be the cause of the inability of the material to electropolymerize.  It is well established that monomer concentration in solution is an important factor for the electrochemical formation of PTs as well as the quality of the subsequent film.39, 43, 136  The inability of the phosphine-capped Au NPs to electropolymerize could be analogous to this effect, where the effective concentration of the oligomer is too low for polymerization to occur.  Another possibility is that the phosphine ligand could be more prone to ligand exchange by the tetrabutylammonium cation from the electrolyte.  According to hard-soft acid-base (HSAB) theory, the Au-S bond is stronger than the Au-P bond.  Though the Au-N bond is still weaker than the Au-P bond, desorption of phosphine ligands from the gold surface is likely to result in exchange due to the relatively high concentration of the tetrabutylammonium cation.137Further work with the phosphine-capped Au NPs was abandoned because of its inability to electropolymerize.       57   Figure 2.6.  CVs for a) 4 and b) 5 in a DCM solution containing 0.1 M [(n-Bu)4N](PF6).  2.3.5 Characterization of Poly(4). UV-vis spectroscopy was used to compare poly(4) to its monomer (Figure 2.7).  The spectrum of 4 (Figure 2.7 red trace) has a strong absorbance at 360 nm from the π*←π transition of the oligothiophene 1 which caps the Au NPs.23, 120  The relative breadth of this peak arises from variations in molecular orientation and packing on the Au NP surface.  It should also be noted that only a small plasmon absorption band is visible in the unpolymerized sample around 520 nm.  This is expected from nanoparticles with an average size of 2.1 nm, as surface plasmon bands are absent in nanoparticles smaller than 2 nm.138  The π*←π transition is shifted in the case of poly(4) (Figure 2.7 black trace) to 440 nm.  This shift reflects the decreased HOMO-LUMO gap in the thiophene chain, consistent with the increase in conjugation length from oligothiophene to PT.24   a) b) 58   Figure 2.7.  UV-vis spectra for 4 (red trace) and poly(4) (black trace).  TEM images of thin poly(4) films grown directly onto copper TEM grids reveal an inhomogeneous film of varying thickness (Figure 2.8a).  The large particles observed are likely clusters of Au NPs and areas where the film happens to thicker.  The Au NPs are distributed throughout the polymer film, as evident in simultaneous TEM-EDX spectroscopy on poly(4) (Figure 2.8c).  The TEM image used for the EDX analysis is shown in Figure 2.8b.  The EDX was performed on the area enclosed by the large red square labeled 2.  The smaller red square labelled 1 was used to reference the image back after each raster scan during the EDX acquisition.  The pixels in Figure 2.8c are 10 nm wide, and the intensity of the yellow colour is an indication of the concentration of Au atoms in the area of the pixel.  The area covered by the yellow pixels in Figure 2.8c match well with the region covered by the polymer in Figure Poly(4) 4 59  2.8b.   This data provide confidence that the observed film is indeed composed of polymerized Au NPs.     Figure 2.8.  a) HR-TEM image of poly(4), b) and c) TEM-EDX of poly(4).  The image in c) corresponds to the large red square numbered 2 in b).  The yellow colour indicates the location of Au atoms.  SEM images of films of poly(4) grown on ITO substrates reveal that the films are composed of two regions of differing morphologies: small nodules which are interspersed a) b) c) 25 nm 60  among areas of densely packed polymer (Figure 2.9a).  Higher magnification images of the nodules region reveal a porous cauliflower-like morphology (Figure 2.9 c, d), whereas the densely packed region shows the initial formation of tiny nodules (Figure 2.9b).  This suggests that the polymer film does not grow homogenously across the entire substrate but rather at specific nucleation sites from which growth occurs at different rates.  Images obtained by Kankare and coworkers from scanning tunneling microscopy of the initial stages of electropolymerization of 3-hexylthiophene onto ITO reveal that nucleation occurs primarily in the vicinity of ITO grain boundaries.18  61   Figure 2.9.  Scanning electron micrographs of poly(4) a) showing the general morphology of the film with magnified images of b) the ‘flat’ region of the film and c,d) of the cauliflower portions.  To quantify the amount of Au in the polymer film, EDX spectra of the films were obtained (Figure A.1a).  The large peaks in the EDX spectra corresponding to Sn, In and Si all originate from the ITO-covered glass substrate due to the analysis depth for EDX (up to 10 µm).  In addition to the peaks originating from the substrate, peaks from S and Au are also observed.  An atomic ratio of Au : S is 0.55 ± 0.05 was calculated, within one standard deviation (Table 2.1).     a) b) c) d) 5 μm 500 μm 10 μm 2 μm 62  The XPS spectrum of poly(4) was also acquired (Figure A.2a).  XPS is a surface-sensitive technique that probes only the outermost 10 nm of a surface and, unlike EDX, interference from the substrate is minimal with this technique.  From the spectrum, the Au : S atomic ratio was calculated, within one standard deviation, to be 0.8 ± 0.2.  The similar Au : S value returned by both techniques suggests that the films are mostly homogenous in Au composition throughout the full thickness of the samples.  The slightly higher Au content measured by XPS might be due to its smaller penetration depth, which could over account for Au NPs at the surface.  Both Au : S ratios calculated for the polymer film calculated from the XPS (0.8 ± 0.2) and EDX (0.55 ± 0.05)  results are consistent with the ratio of monomer 4 (0.7 ± 0.2 by XPS, 0.7 ± 0.1 by TGA), indicating that minimal or no loss of ligand occurs during the polymerization process (Table 2.1).  In particular, the results measured by XPS are self-consistent.  2.3.6 Etching of Poly(4). Removing the Au NPs post-polymerization was accomplished by exposing the poly(4) films to a DCM  solution containing 0.05 M [(n-Bu)4N]I and 0.05 M I2 .  This mixture is based on a common Au etchant used in microfabrication processes, an aqueous potassium iodide and iodine solution,139 in which the iodine species exist in equilibrium between molecular iodine and the triiodide anion:140 Equation 2.3.                                         63                                                                                                                                                                                                                       The etching process proceeds by oxidizing the gold to a gold iodide complex according to the following half-reaction: Equation 2.4.                                          The oxidation is balanced by reduction of triiodide to iodide: Equation 2.5.                                         Giving the net reaction:  Equation 2.6.                                          The gold iodide salt is removed by rinsing the electrode.  During the etching process, the polymer is also doped by the triiodide species.  The doping is reversible and does not have an appreciable effect on the electrochemical behavior of the polymer.  Reversible doping of conducting polymers with halogens, and iodine in particular, has been known since the seminal work of Heeger, Shirakawa, and McDiarmid on polyacetylene.20,19      Figure 2.10 shows the effect of etching on Au NP-PT hybrid films.  The images were taken after 10 minutes of exposure to the etching solution.    Poly(4) films remain intact on the ITO electrode after the etching process (Figure 2.10b).  The poly(4) film persists even up to 1 hour in the etching solution.  Cracks are present in the poly(4) films before etching which 64  appear to be caused by the thin films drying very quickly after removal from the DCM rinsing solution.  The cracks are much worse after the etching process.  The films are thin and are prone to delamination from the ITO surface.  The films change in colour from the brown seen in undoped poly(4) films to a red colour reminiscent of undoped PT.  Films of poly(6), deposited from 6 donated by former Wolf group colleague Dr. Sih,120 were also exposed to identical etching conditions.  The surface of 6 is passivated by 3, a terthiophene functionalized at the 2- position by a phosphino group (Figure 2.1).  During electropolymerization of 6, the capping groups are limited to forming sexithiophene oligomers (dimers of 3) because only one α- position of the monomeric terthiophene is unfunctionalized.  The poly(6) film can be thought of as individual sexithiophene groups connected through Au NPs.  Because of this, the bulk of poly(6) films (Figure 2.10a) do not survive the etching process.  Some trace amounts of polymer, stained by the etching solution, appear to remain attached to the ITO, though the vast majority of the film has been removed.  Once the Au NPs are etched, the individual sexithiophene groups can be dissolved into the DCM solution.  This demonstrates the need for the oligothiophene capping group to be substituted at the 3' position, which allows for polymerization through both α- positions of the terminal thiophenes.    65   Figure 2.10.  Films of a) Poly(6) and b) Poly(4)  before and after etching for 10 minutes.  In order to monitor the degree of Au removal from exposing poly(4) to the etching solution, the EDX (Figure A.1b) and XPS (Figure A.2b) spectra for the films were collected after etching.  In the EDX spectrum after etching the peaks corresponding to gold are drastically reduced in intensity.  The degree of etching was inconsistent from film to film but in the least etched film, the Au content dropped by a factor of 5.  Similarly in the XPS spectrum, there is a decrease in the amount of Au in the films.  Again, there was a varying degree of etching between films but in the minimum case, the Au content decreased by a factor of 15.  Considering that XPS preferentially probes the surface of the film, the lower Au:S ratio measured using this technique suggests that etching occurs more readily at the surface of the film.   a) BEFORE b) AFTER AFTER BEFORE Poly(6) Poly(4) 66  Table 2.1.  EDX and XPS results for the gold content of poly(4) before and after etching. Sample   Au : S ratio EDX                           XPS                          TGA 4 - 0.7 ± 0.2      0.7 ± 0.1 Poly(4) 0.55 ± 0.05 0.8 ± 0.2 - Poly(4) etched 0.07 ± 0.05 0.03  ± 0.02 -  2.3.7 Electrochemistry of Poly(4) Before and After Etching. The electrochemical behavior of the poly(4) films were investigated by cyclic voltammetry.  In the forward scan of the voltammogram of the unetched polymer film (Figure 2.11 blue scan), the onset of the current increase is at 0.5 V, with a peak at 0.65 V.  Upon reversal of the scan, the corresponding reduction peak is at 0.65 V.  The general shape of the voltammogram is characteristic of reversible p-doping and dedoping of PT.    The high oxidation potential of the monomer could also lead to degradation of the polymer during the polymerization process, the ‘polythiophene paradox’,41 and could contribute to the higher oxidation potential of the resulting polymer film.   a) 67   Figure 2.11.  CV of poly(4) before etching (blue trace) and after etching (red trace) at 25  mV s-1.  Etching of poly(4) results in diminished electroactivity of the polymer films (Figure 2.11 red trace).  The onset potential for oxidation of the polymer occurs at 0.6 V and no oxidation peak is observed.  In the reverse scan, the reduction peak occurs at 0.7 V.  There is a decrease in the charge stored in the film after etching as well.  In an unetched film, electron transport can occur through the Au NPs and the PT chains concurrently.120  Removal of the Au NPs leads to lower rate of electron transport and can also lower the effective conjugation length of polymers that are connected through the Au NPs.   Because the loss of electroactivity of the films is expected to overwhelm any improvements in ion diffusion, poly(4) was not further pursued for use in supercapacitors.  Rather, a blend of the Au NPs with another conducting polymer, EDOT, was explored Poly(4)  Poly(4) etched 68  (discussed in Chapter 3), wherein most of the capacitance of the films was expected to be from conducting polymer which should not be affected by the etching process.    2.4 Conclusions. In this chapter, the preparation and characterization of two oligothiophene-capped Au NPs, 4 and 5, were described.  It was found that fewer capping ligands were required to passivate the Au NP surface with the phosphino-capped oligothiophene 2 relative to the thiol-capped oligothiophene 1.  This was further examined by forming 2D SAMs of the capping oligothiophenes on flat gold electrodes and it was discovered that unlike the thiol oligothiophenes, the phosphino-oligothiophenes did not pack efficiently into a dense monolayer.  The thiol-capped Au NPs were electropolymerized and the Au NPs-oligothiophene hybrid films were characterized using imaging and elemental analysis techniques, the results from which suggest that the polymer film maintain the same composition as that of the Au NP monomers.  The Au NPs were selectively removed from the films with exposure of the films to an iodide/triiodide etching solution.  In order to validate the hypothesis that the capping ligands needed to be functionalized at the 3'- position, films of poly(6), where the capping ligand is functionalized at the 2- position were deposited and exposed to the etching solution.  Unlike the poly(4) films, the poly(6) disintegrated after etching,  This is because the terthiophene group capping 6 is functionalized at the 2- position and is thus only capable of dimerization.  Removal of the Au NPs leave behind short oligomers which are dissolved off of the electrode.  The degree of etching was monitored using elemental analysis and though there was limited control on the rate of etching, the Au content decreased 69  by a factor of 8 and 26, as measured by EDX and XPS, respectively.  The difference in these values measured by the two techniques suggest that etching of the Au NPs is occurring more rapidly at the polymer surface.  The electrochemical behaviour of the polymer films was explored before and after etching.  Prior to etching, the voltammogram of the polymer showed the typical redox behaviour of a PT.  After etching, there was a decrease in the redox current and an anodic shift in the onset potential of oxidation.  Because the Au NPs occupy much of the polymer volume, their removal from the film likely disrupts conjugation pathways between polymer chains.       70  Chapter 3 PEDOT-4 Copolymers   3.1 Introduction. In the work described in Chapter 2, a significant decrease in the redox current of poly(4) was observed after etching of the Au NPs.  In poly(4), the Au NP core constitutes a significant volume of the polymeric film; dissolution of the Au NPs likely results in disruption of the conjugation of the polythiophene, resulting in shorter oligomeric chains.  In this Chapter, the co-polymerization of 4 with EDOT is described, with the intent of creating hybrid PEDOT-4 films.  During electropolymerization, an EDOT molecule can undergo polymerization with either another EDOT molecule or couple to one of the oligothiophenes on the surface of 4.  The copolymerization should allow for a distribution of the Au NPs throughout the polymer volume.  Some control over the composition of the PEDOT-4 hybrid film should be possible as well by varying the relative ratios of EDOT and 4 in the monomer solution. It was expected that by lowering the content of the Au NP sacrificial template, the negative impact on the capacity of the film would be minimized, while still allowing for improvements in ionic conductivity.  PEDOT was chosen as the conducting polymer component because it may be both p- and n-doped due to its low bandgap141, 142 and is highly conductive, up to 500 S cm-1.143  In the co-polymer, the majority of the capacity would originate from the PEDOT, with the Au NPs serving as a sacrificial template.   PEDOT-Au NP hybrid materials have previously been prepared by using PEDOT or EDOT to reduce Au salts in situ,144, 145 by spin coating Au NPs onto PEDOT,146 using Au NPs capped with EDOT oligomers,120 or by dipping the polymer in a colloidal solution of NPs.147  In this Chapter, a method similar to the one used by Mathiyarasu148 was selected, wherein 71  EDOT is polymerized in the presence of preformed Au NPs.  This provides control of Au NP size, allows the Au NPs to be embedded throughout the volume of the polymer and offers the potential to alter the polymer-Au NP ratio by varying their ratio in the monomer solution.  Because the Au NPs used here are capped with oligothiophenes, and thus can be electropolymerized,120 the Au NPs should become uniformly embedded throughout the entire polymer volume.     3.2 Experimental. 3.2.1 General.  Chemicals were purchased from Aldrich, except for HAuCl4.3H2O which was purchased from Strem Chemicals and EDOT which was a gift from Bayer.  All chemicals were used as received except EDOT which was distilled prior to use and [(n-Bu)4N]PF6, which was recrystallized three times from hot EtOH and dried in vacuo at 100 °C for 5 days.  Celgard 2500 separator was a gift from Celgard LLC.  Indium-tin oxide (ITO) coated unpolished float glass (Rs = 4 – 8 Ω) was purchased from Delta Technologies.  Glassy carbon working electrodes (2 mm diameter) and Ag/Ag+ non-aqueous reference electrodes were purchased from BASi.  A 0.1 M [(n-Bu)4N]PF6, 0.01 M AgNO3 MeCN solution was used in the non-aqueous reference electrode.  All reactions were performed in an inert N2 (99.0 %) atmosphere using standard Schlenk technique with dry solvents, unless otherwise stated.  Electropolymerization, cyclic voltammetry and galvanostatic charging experiments were performed using a Brinkmann PGSTAT12 Autolab potentiostat.  Electrochemical impedance Spectroscopy (EIS) was performed using a Solartron 1260 Impedance/Gain Phase Analyzer in 72  conjunction with a Solartron 1287 Electrochemical Interface.  Data were collected using 10 mV AC amplitude within the frequency range from 0.1 Hz to 1 MHz, taking 10 points per decade.  Before each measurement, the electrode was held at the experimental DC potential for a minimum of five minutes.  Fitting of the EIS data was attempted using EIS Spectrum Analyzer software.  TEM was performed using a Hitachi H7600 Electron Microscope operating at 100 kV.  A solution or suspension of Au NPs was dropcast onto 300-mesh carbon-coated copper grids.  In order to obtain micrographs of PEDOT and PEDOT-4 films, the polymer was carefully removed from the ITO substrate using a razor blade, sonicated in acetone for 5 minutes and the suspension was dropcast onto the carbon-coated copper grid.  SEM and EDX spectroscopy was performed using a Hitachi S-3000N electron microscope on polymer samples deposited on ITO. The polymer films were oxidized to 1V prior to acquiring their SEM images in order to increase the conductivity of the films.  Sizing of the particles was done using ImageJ software from 100 particles from at least three different TEM images.    3.2.2 Electropolymerization of PEDOT and PEDOT-4 films.  The PEDOT and PEDOT-4 samples were prepared by electropolymerization via cyclic voltammetry.  A 0.05 M EDOT, 0.1 M [(n-Bu)4N](PF6) DCM solution was degassed via three freeze-pump-thaw cycles.  Glassy carbon or an ITO-coated float glass slide was used for the working electrode. Ag/Ag+ (0.01 M) and a platinum mesh were used as the reference and counter electrodes, respectively.  PEDOT samples were prepared by cycling the potential of the working electrode from 0 to 1.8 V twenty times.  PEDOT-4 samples were prepared from the identical EDOT monomer solution but with 4 added.  Depending on the desired amount of Au NPs in the PEDOT-4 film, the concentration of 4 in the monomer solution varied from 0.1-73  2 mg/ml while the EDOT concentration was maintained at 71 mg/ml.  Glassware was cleaned primarily using a basic bath of 2 M KOH in 3:1 (v/v) isopropanol:water, followed by rinsing with concentrated HCl.  If after this step, the glassware still appeared to be dirty (due to Au NPs or other impurities), the glassware would be cleaned by soaking in aqua regia overnight.   The PEDOT and PEDOT-4 modified electrodes were tested in monomer-free solution of 0.1 M [(n-Bu)4N]PF6 or [(n-Bu)4N]BPh4 in PC using a Ag/AgNO3 (0.01 M) and a platinum mesh were used as the reference and working electrodes, respectively.    3.2.3 Construction of Supercapacitor.   Supercapacitors were constructed in a symmetrical Type I configuration (Figure 3.1) using PEDOT-4 films deposited onto a substrate of ITO-covered float glass.  Prior to assembly, the cathode was doped at 0.75 V for 10 minutes in a 0.1 M [(n-Bu)4N]PF6 MeCN solution in a three electrode set-up.  Similarly, the anode was dedoped at -1 V for 10 minutes.  The two polymer films were pressed together, separated by a Celgard 2500 membrane.  Prior to construction, the separator membrane had been soaked for 24 hrs in a gel-polymer electrolyte solution composed of, by weight, 70% MeCN, 20% PC, 5% PMMA, and 5% [(n-Bu)4N]PF6.  Conducting tape was added to the end of the device to improve contact between the ITO and the alligator clamps on the leads.  The ITO was weighed pre- and post-polymerization on a microbalance to get an estimate on the polymer weight.      74   Figure 3.1.  Architecture of test polymer-based supercapacitors, composed of ITO-covered float glass (grey), polymer at both the anode and the cathode (red) and the PMMA membrane separator (blue).  3.2.4 Digestive Ripening of Au NPs. In order to try to increase the diameter of the Au NPs, two different methods were used to digestively ripen the oligothiophene-capped Au NPs according to a modified procedure.128   In the first method, 4, [(n-Bu)4N]Br and 1 were heated to 160 °C in a N2 atmosphere for 6 hours.  Over the course of the ripening, the molten solution turned from black to a dark red in colour.  In the second method, 4 and 1 were dissolved in o-dichlorobenzene (2 ml) and heated to 160 °C in a N2 atmosphere for 6 hours.  The solution turned from black to a deep purple in colour.  For both methods, the particles were purified by rinsing with a 1/10 (v/v) DCM : hexanes solution and filtering.  This was repeated until the filtrate was clear.    3.2.5 Synthesis of hexanethiol-capped Au NPs. 120 nm hexanethiol-capped Au NP   The hexanethiol-capped Au NPs were synthesized according to a modified procedure of Osterloh and co-workers.149  To 500 mL of a boiling 120 mM octylamine toluene solution at 90 ºC, 5 mL of a 1.2 M HAuCl4 toluene solution were added.  Upon addition of HAuCl4, the 75  solution changed color, first from clear to red, then to yellow and finally back to clear.   The solution was heated to the boiling point for 2 hours and then quenched by addition of methanol.  The methanol was removed in vacuo, and the toluene solution was heated to boiling after the addition of excess hexanethiol (6 mL) for 2 hours.  The thiol-capped Au NP precipitated out of solution as a black solid, which was subsequently isolated by filtration and washed with ethanol.  The 1H NMR of the product showed no evidence of any residual unbound hexanethiol or octylamine.  3.2.6 Electrodeposition of PEDOT-Au NP films with hexanethiol-capped Au NPs.  The deposition of the PEDOT/Au NP blends was performed using a DCM (10 ml) solution containing 1 M EDOT, 10 mg of Au NPs, and 0.1 M [(n-Bu)4N]PF6.  A Pt disk working electrode (1 mm diameter), Ag wire pseudoreference electrode and Pt mesh counter electrode were used.  The deposition was performed potentiostatically at 1.2 V until 2 mC of charge had passed.  The polymer deposited onto the Pt disk electrode was then rinsed carefully three times with DCM and left to dry in the ambient laboratory environment before use.   In order to analyze the films for TEM analysis, the PEDOT-Au NP films were prepared by depositing the PEDOT directly onto a Cu TEM grid immersed in the electrolytic solution.     76  3.3 Results and Discussion. 3.3.1 Electropolymerization of PEDOT and PEDOT-4 films. The PEDOT-4 and PEDOT films were electrochemically deposited under potentiodynamic conditions.   When deposited under identical conditions, PEDOT-4 films were optically thicker and less prone to delamination than the poly(4) films of Chapter 2.  The PEDOT-4 films weighed on average 0.8 ± 0.2 mg over a 2 cm2 device.  Using the assumption that PEDOT-4 films have a similar density as PEDOT, 1.34 g cm-3, the deposited films are 0.30 ± 0.07 µm thick.  Both, the PEDOT and PEDOT-4 films were blue in colour in the dedoped state.   TEM micrographs of the PEDOT-4 films show flakes of polymer with embedded Au NPs (Figure 3.2a,b,c).  The Au NPs appear to be distributed randomly throughout the polymer, though they are most clearly visible at the edges where the polymer is thinnest (Figure 3.2d).  The diameter of the features in the TEM corresponding to the Au NPs is larger than those of 4, suggesting that agglomeration of the Au NPs occurs during the course of the electropolymerization.    77   Figure 3.2. TEM images of PEDOT-4 films.  The Au NP content of the PEDOT-4 film was determined using EDX and XPS (Table 3.1).  The ratio of 4 to EDOT in the monomer solution before electropolymerization was varied incrementally to see if the Au NP content of PEDOT-4 could be adjusted.  Table 3.1 shows that there is a background signal for Au in the EDX even in films that were grown as pure PEDOT.  This is likely contamination from the washing step of the films, where the solution a) b) 100 nm 100 nm 100 nm c) d) 20 nm 78  might contain AuI2- from previous samples.  Contamination from Au NPs on the glass ware is another possibility for the presence of Au in the pure PEDOT samples.  At the lowest Au NP loading in the feedstock, the amount of Au NPs incorporated into the polymer is insignificant.  As expected, the amount of embedded Au NPs increases with the addition of Au NPs.  The volume ratio of Au NP to PEDOT can be calculated based on the diameter and assuming a density of 1.34 g cm-3 for PEDOT,150 a spherical shape for the Au NPs and that there are no Au NPs present in the pure PEDOT sample.  An example calculation is presented in the appendix (Equation A.1-Equation A.4) for the sample with the highest Au NP loading.  The EDX values were used for the calculation as the ratios are representative of the entire polymer film, whereas XPS is a surface-sensitive technique.  The higher Au / S values from the XPS results suggest that the Au NPs are not distributed continuously throughout the polymer but are concentrated at the surface.  This could be due to EDOT depositing first and forming the initial polymer layers on the electrode due to its lower oxidation potential.       Table 3.1.  EDX and XPS results for the gold content of polymer films with addition of 4 in the monomer solution. Monomer     Au : S  Percent Volume of Au NPs EDX XPS 71 mg/ml EDOT 0.028 ± 0.009 0.033 ± 0.006 0 71 mg/ml EDOT + 2 mg 4 0.02.9 ± 0.002 0.047 ± 0.009 0.019  71 mg/ml EDOT + 5 mg 4 0.052 ± 0.005 0.153 ± 0.007 0.66 71 mg/ml EDOT + 10 mg 4 0.076 ± 0.002 0.309 ± 0.004 1.4  Attempts to load the polymer with more Au NP were unsuccessful as 4 was not soluble in DCM beyond the highest concentration shown.  In all further examples, PEDOT-4 films were prepared with the addition of 10 mg of 4. 79  3.3.2 Effect of etching on PEDOT-4 films. In order to optimize the time that the PEDOT-4 is etched, the Au : S ratio of the PEDOT-4 blend was analyzed as a function of time based on the atomic ratio calculated from the XPS spectra.  The %Au content of each etched films were normalized to the initial Au content of the as-prepared films (no etching).  Initially, the Au content decreased very rapidly upon etching but then leveled out after 2 minutes (Figure 3.3).  From this data, it was determined that the etching time for the PEDOT-4 would be kept at 3 minutes in order to maximize the removal of the Au and to minimize the exposure time of the films.        Figure 3.3.  Effect of etching time on the Au : S ratio of PEDOT-4.  The initial Au content was set at 100%, and all other values are relative to this.   80  The effect of etching on the PEDOT-4 film is evident from the TEM images after etching.    After 3 minutes, the dissolution of the Au NPs results in the formation of nm-sized pores (Figure 3.4 a,b).  From the images, it is clear that etching is incomplete as some Au NPs are still visible in the micrographs.  Samples that were etched for 20 minutes showed a more complete etching (Figure 3.4 c,d).  However, when the PEDOT-4 modified electrodes were etched for 20 minutes there was a noticeable loss in electroactivity in the film.  Visually, the polymer film remains intact which suggests that the etching solution either has some detrimental effect on the polymer connectivity or is degrading the polymer.  Section 3.3.4 addresses the issue of the effect of the etching solution on the polymer in greater detail.     81   Figure 3.4.  TEM images of PEDOT-4 films after etching for a), b) 3 minutes and c, d) 20 minutes.  The UV-vis spectra of thin films of PEDOT and PEDOT-4 are presented in Figure 3.5.  The λmax for PEDOT is significantly red-shifted relative to the PEDOT-4 film (606 and 550 nm, respectively).  This suggests that the effective conjugation length of the polymer in the PEDOT-4 films is shorter than in PEDOT.   After etching λmax of PEDOT-4 is red-shifted to a) 100 nm b) 100 nm 100 nm c) d)  m 100 nm 82  574 nm.  This is consistent with the effective conjugation length of the polymer being disrupted by the Au NPs in the film.  The Au NPs can act as an electron reservoir, removing electrons from the polymer film, doping the polymer resulting in a shift from a benzenoid to a quinoid structure.  The absorbance of the PEDOT-4 films at higher wavelengths (> 750 nm) shows evidence of doping of the PEDOT from the Au NPs even after dedoping at -1 V.  The large background absorbance for the PEDOT-4 films before and after etching is likely from light scattering, suggesting that the PEDOT film has higher surface roughness when electropolymerized in the presence of 4.      Figure 3.5. UV-vis absorption spectra for thin films of polymer deposited onto ITO.  0.250.30.350.40.450.50.550.60.65350 450 550 650 750AbsorbanceWavelength / nmPEDOTPEDOT-4PEDOT-4 etched83  The voltammograms of the pure PEDOT films that were grown as a control under identical conditions to the PEDOT-4 films are presented in Figure 3.6. At a scan rate of 10 mV s-1, the major anodic peak of the PEDOT film occurs at -0.4 V (Figure 3.6a).  At higher potentials, the current plateaus and is characteristic of capacitive behaviour.  The p-doping of the polymer initially involves a flux of solvent from the polymer followed by the incorporation of the charge-balancing anions.79  The cations do not appear to be involved in the charge balancing process, although there is some evidence for cations being involved in the p-doping process for other conducting polymers such as polypyrrole.151, 152  Upon reversal of the scan, dedoping of the PEDOT occurs at -0.8 V.  The current decreases sharply at this point, indicative of the end of the capacitive regime for PEDOT.   84   Figure 3.6.  CVs of PEDOT-modified glassy carbon electrodes at a) 10 mV s-1, b) 100 mV s-1, c) 500 mV s-1 for the wide potential regime and at d) 10 mV s-1, e) 100 mV s-1 and f) 500 mV s-1.  The blue scan and red scans represent the sample before and after etching.  When the polymer is cycled in a narrower potential window, the voltammogram for PEDOT shows an almost ideal rectangular double layer capacitive shape (Figure 3.6d).  At a) d) b) e) c) f) 85  higher scan rates (Figure 3.6c,f), a delay in the current switching time is observed because the charging kinetics are slower than the scan rate.  This most clearly seen at the switch from the forward to reverse scan where there is a delay for the material to reach the maximum current at the higher scan rates.  This is attributed to the relatively slow diffusion of counterions into the polymer volume, limiting the charging rate.  This issue manifests itself as a decrease in the total energy stored at high power demands.   Exposing the PEDOT film to the [(n-Bu)4N]I/I2 etching solution results in only small changes in the voltammograms.  It is believed that these changes can be ascribed to the normal loss of capacitance evidenced in most polymer films upon repeated scans and not as a result of etching of the film.89, 153   The PEDOT-4 film shows electroactivity very similar to the pure PEDOT films, with doping and dedoping occurring at the same potentials (Figure 3.7).  This suggests that at low Au NP loadings, the Au NP has very little effect on the electrochemical behaviour of the overall polymer film.  At the highest scan rate (Figure 3.7c, f), the etching appears to very slightly enhance the switching speed of the films, which would indicate a small improvement in the ionic mobility of the counterion, though the effects were minimal. 86    Figure 3.7.  CVs of PEDOT-4-modified glassy carbon electrodes at a) 10 mV s-1, b) 100 mV s-1, c) 500 mV s-1 for the wide potential regime and at d) 10 mV s-1, e) 100 mV s-1 and f) 500 mV s-1.  The blue scan and red scans represent the sample before and after etching.  a) d) b) e) c) f) 87  3.3.3 Effect of Electrolyte Size.   The match between pore size and anion size can have a very large effect on the apparent electrochemical behaviour of supercapacitors.154, 155  Large pores combined with small anions should allow for faster charging and discharging rate of the supercapacitor.  As the cation is not involved in the intercalation process, its size effect is minimal.  Table 3.2 summarizes the partial molar volumes for some important anions in both MeCN and PC.  The largest anion, BPh4-, will be more difficult to intercalate into the PEDOT during doping than the chloride anion.    Table 3.2.  Partial molar volume of anions at 25 °C.156 [(n-Bu)4N]+ anion Partial Molar Volume (cm3 mol-1) MeCN PC Cl- 3 16 BF4- 31 43157 ClO4- 34 44 PF6- 56158 72 BPh4- 273 284   In order to enhance the effect on ion mobility via etching of PEDOT-4, the polymer-modified GCE electrodes were tested in PC using the [(n-Bu)4N]BPh4 electrolyte (Figure 3.8).  These results can be compared with the identical electrodes tested with [(n-Bu)4N] PF6 (Figure 3.7).  Firstly, the current of PEDOT-4 electrodes is an order of magnitude lower in the [(n-Bu)4N]BPh4 solution of the solution.  Presumably this is due to the lower ionic mobility of the tetraphenylborate anion, which cannot intercalate into the polymer as easily as the smaller hexafluorophosphate anion.  In Figure 3.8a, a large oxidation wave is observed with its onset at 0.2 V.  Presumably this is the anodic edge of the solution potential window.  The effect of 88  etching is also more pronounced in these films, even at slow sweep rates (Figure 3.8a).  This is consistent with the large BPh4 being more difficult to intercalate into the PEDOT-4 film, and an increase in porosity of the polymer can enhance the ionic mobility.  At fast scan rates (Figure 3.8c), the effect of etching is minimized which is the opposite of what was observed with the PF6- anion.  The lower ionic mobility of the tetraphenylborate anion relative to the hexafluorophosphate anion can help explain this observation.  As the scan rate is increased, eventually a scan rate will be reached where the improvements in the ionic mobility will be overwhelmed by the rate of charging / discharging.  This threshold scan rate will be lower for ions with lower ionic mobility.  The scan rate of 500 mV s-1 might be faster than the threshold scan rate for the tetraphenylborate but not the hexafluorophosphate anion.  The diminished capacitance for the film after etching at the faster scan rate could be the result of the etching leading to a less conductive film with only marginal improvements in the ionic mobility.    89   Figure 3.8.  CVs of PEDOT-4-modified glassy carbon electrodes at a) 10 mV s-1, b) 100 mV s-1, c) 500 mV s-1 for the wide potential regime and at d) 10 mV s-1, e) 100 mV s-1 and f) 500 mV s-1.  The blue scan and red scans represent the sample before and etching, respectively.  3.3.4 Electrochemical impedance Spectroscopy on PEDOT and PEDOT-4 Films. Electrochemical impedance spectroscopy was used in order to further analyze the PEDOT and PEDOT-4 films before and after etching.  The films were analyzed at different potentials, which allowed for analysis of the polymers in their doped and undoped states.   The Nyquist plots for PEDOT films at -1 V (undoped) and 0.5 V (doped) are shown in Figure 3.9.   c) b) a) 90   Figure 3.9. Nyquist plots of EIS results for PEDOT at a,b) -1 V and at c,d) 0.5 V.  Plots b) and d) are magnified versions of a) and c), respectively, highlighting the high frequency regime.  Fits of the data to the conventional circuit models (Randles or transmission line) were not successful.  The high-frequency semi-circle is slightly raised above the x-axis, which is unusual and a good model could not be found to account for this.  A depressed semi-circle is often attributed to non-ideal behaviour of the capacitor and is typically modelled using a constant phase element.  The near vertical line of the Nyquist plot for PEDOT at 0.5 V (Figure a) b) c) d) 91  3.9c) at low frequencies is indicative of capacitive processes.  This is not observed in Figure 3.9a, when the PEDOT has been dedoped at -1 V, confirming that the PEDOT undergoes a transition from insulating to conducting states.  In Figure 3.9c and Figure 3.9d, the high frequency regime has been highlighted.  In both the doped and undoped states, a pseudo-semi-circle is observed at high frequencies.  The presence of the semi-circle is often modeled by a resistor in parallel with a capacitor (or constant phase element).  The radius of the semi-circle corresponds to the charge transfer resistance, RCT.  In both the doped and undoped state, this resistance increased upon etching (Table 3.3).  This suggests that the iodide/triiodide solution does have a negative effect on the polymer, which was not observed from the CV results shown in Figure 3.6.  The iodide/triiodide redox couple is often used in dye-sensitized solar cells in conjunction with a PEDOT electrode with no mention of degradation of PEDOT by iodide/triiodide.159-163  Girtu and co-workers did observe that iodine species can become trapped in the PEDOT film, with blocking of the electrode surface.164  This could potentially explain the effect on the RCT of the PEDOT film by the etching solution.  The additional washing and drying of the electrode could cause a physical degradation of the polymer film as well, resulting in increased RCT.  The high frequency x-intercept is the solution resistance, Rs.   The Nyquist plots for PEDOT-4 films at -1 V (undoped) and 0.5 V (doped) are shown in Figure 3.10.  The PEDOT-4 films also transition from an insulating to a conducting state from -1 V to 0.5 V, as evidenced by the presence of the near vertical line at low frequencies in Figure 3.10c.  In the undoped state, etching of the film causes an increase in the radius of the high-frequency semi-circle (Figure 3.10b).  However, in the doped state, the etching actually decreases the radius of this semi-circle (Figure 3.10d).  The resistance to charge transfer has both an ionic and electronic component, which could account for the different effect of etching 92  at the different doping levels of the polymer.  At low doping levels, the ionic contribution to the charge transfer resistance is low compared to the electronic contribution.  Any negative effect on the electronic resistance would result in an increase in the RCT.  However, in the doped state, the improvement in ionic conductivity of the polymer can overcome the negative effect on the electronic conductivity.  Notably, the PEDOT films exhibit an increase in RCT in both the doped and undoped state as the exposure to the etching solution would not result in any improvement in ionic mobility.   93   Figure 3.10. Nyquist plots of EIS results for PEDOT-4 at a,b) -1 V and at c,d) 0.5 V.  Plots b) and d) are magnified versions of a) and c), respectively, highlighting the high frequency regime.  Table 3.3 is a compilation of the results based on the Nyquist plots of PEDOT and PEDOT-4 films.  These values are not derived from circuit models fitted to the data but from points where the plot intercepts the x-axis or from the radius of the semi-circle.   a) b) c) d) 94  Table 3.3. Parameters derived from EIS results of PEDOT and PEDOT-4 films.  Rs (Ω)  at -1 V Rs (Ω)  at 0.5 V RCT (Ω)  at -1 V RCT(Ω)  at 0.5 V PEDOT 12 ± 5 4 ± 3  284 ± 5 211 ± 6 PEDOT etched 18 ± 4 9 ± 5 307 ± 9 230 ± 10 PEDOT-4 7 ± 4 3 ± 2 314 ± 6 226 ± 8 PEDOT-4 etched 9 ± 2 2 ± 1 353 ± 4  196 ± 9  3.3.5 Supercapacitor-based on PEDOT-4 Films.   Supercapacitors based on the PEDOT-4 films were constructed based on the Type I configuration as described by Rudge (Figure 3.11).90  This is a symmetric configuration with the same active material at both electrodes.  In the fully charged state of the supercapacitor, the polymer at the cathode is in the fully doped state whereas the polymer at the anode is in the fully dedoped state.  As the supercapacitor discharges and the potential difference between the electrodes decreases, the polymer at the cathode is dedoped and the polymer at the anode is doped.  The electrode fabrication was similar to the one described by Wudl with a gel-polymer electrolyte-infused separator between two polymer electrodes.165  Because the device was not sealed, a viscous gel allowed for minimal evaporation of the solvent over the course of the experiment.  However, long term cycling was not possible because of loss of solvent.  The higher viscosity of the gel relative to a solution without PMMA leads to a decrease in the ionic mobility of the electrolyte.  This in turn should lead to more pronounced improvements in charging / discharging kinetics after etching as the mobility of the ions will be even more limiting.     95   Figure 3.11. Pictures of a PEDOT-4 device a) top-down and b) side-view.  The supercapacitor was cycled from a cell potential of -0.5 V to 0.5 V (Figure 3.12).  At slow scan rates the supercapacitor shows the near-ideal capacitive behaviour (Figure 3.12a).  These shape of the voltammograms become skewed at the higher scan rates, symptomatic of the ion-diffusion limited kinetics.  This is improved in the etched samples where the increase in current upon switching from the forward to the reverse scan occurs much more quickly than in the non-etched samples (Figure 3.12b, c).  A redox peak from the remnant iodide/triiodide couple is evident in the etched samples at -0.15 V.  The current profile during the discharging of a capacitor is governed by Equation 3.1:5  Equation 3.1. 𝑖(𝑡) = 𝐼0𝑒(−𝑡𝑅𝐶)  Where t is time in s, i(t) is the current at time t, I0 is the initial current, R is the resistance in Ω and C is the capacitance in Farads.  Over a small potential range in the CV, a plot of the natural a) b) 96  logarithm of current against time can be generated, with the slope equal to (-1/RC).  The RC time constant is a figure of merit for the charging and discharging rates of a capacitor, with a smaller time constant equalling a faster rate.  Linear traces are obtained for both the etched and unetched devices when discharging at 10 mV s-1 from 0.5 V (Figure 3.12d).  RC time constants of 0.93 s and 0.59 s were calculated for the unetched and etched PEDOT-4 devices, respectively.  A 35% decrease in the RC time constant is observed for the device after etching, consistent an improvement in the ionic mobility of the film.      97   Figure 3.12.  CVs of PEDOT-4 supercapacitors (black trace) and etched PEDOT-4 supercapacitors (red trace) at a) 1 mV s-1 b) 5 mV s-1 c) 10 mV s-1.  The plot of the current response as a function of time for the 10 mV s-1 scan rate is shown in d)..    The Ragone plot graphically shows the effect on the energy density of the material as the power demands are increased.  For the etched samples, the drop-off in the energy density is less than in the non-etched sample at the higher power demands (Figure 3.13).    a) b) c) d) 98   Figure 3.13.  Ragone plot of supercapacitors from PEDOT-4 (blue trace) and etched PEDOT-4 (red trace).  3.3.6 Attempts at Larger Nanoparticle Size. In an attempt to create larger pores and enhance the improvements in ion diffusion, the synthesis of larger 4 was targeted.  Attempts at tuning the nanoparticle diameter by adjusting the ratio during the Brust synthesis were unsuccessful as particles only up to 2.5 nm were achieved.  The Turkevich method166 of Au NP synthesis using an amine capping ligand, which typically forms nanoparticles in the 20-200 nm range, followed by ligand exchange by 1137 was explored but resulted in insoluble nanoparticles.   The other approach used was digestive ripening of the as-formed 4.  Small Au NPs are heated to 160 °C, and the small particles agglomerate to form larger nanoparticles.  The first attempt involved heating the particles in a melt of excess [n-(Bu)4N]Br in the presence of 1.  The resulting material proved to be insoluble in DCM.  TEM images from a suspension of the resulting particles showed not only growth of the particles (Figure 3.14a) but a majority of 99  large irregular agglomerates (Figure 3.14b).  Along with the gold metal core, there appears to be a coating around the nanoparticles which is not apparent in the smaller particles.  It is speculated that this could be a result of thermal polymerization of the capping ligand.  This could explain the lack of solubility of the ripened nanoparticles.           Figure 3.14.  TEM images of ripened 4 in the presence of excess 1 and [(n-Bu)4N]Br.  Adjusting the ripening conditions, the particles were heated without [n-(Bu)4N]Br and using minimal o-dichlorobenzene as solvent.  The solution changed from black to a dark purple in colour during the course of the ripening, suggesting an increase in nanoparticle diameter.  The UV-vis spectrum of the solution (including the excess free 1) shows not only a π*←π absorption from the ligand but also a plasmon absorbance band at 732 nm, consistent with a growth in NP size (Figure 3.15).  This was further confirmed from the TEM images (Figure 20 nm 20 nm a) b) 100  3.16) which show much larger inhomogeneous nanoparticles.  Unfortunately, upon purification these particles were minimally soluble in DCM.    Figure 3.15.  UV-vis absorption of ripened 4.   Figure 3.16.  TEM images of ripened 4 in the presence of excess 1.  a) b) 2 µm 500 nm 101  Further attempts at larger nanoparticles were abandoned as it was decided that the low capping efficiency of the 1 precludes its ability to solubilize the larger nanoparticles.  A ligand with a long tether between the oligothiophene end and the capping end might pack more efficiently on the nanoparticle surface and improve the solubility to the point where larger Au NPs could be soluble.    3.3.7 PEDOT-Au NP films with alkylthiol-capped Au NPs. In order to enhance the effect of etching the sacrificial template, very large Au NPs were targeted.  While the Brust synthesis of Au NPs does allow for some control over the Au NPs size, it typically yields particles of diameter less than 5 nm.  The Turkevich method of Au NP166 synthesis yields water soluble colloidal Au in the 10 – 20 nm range.  Exchanging the citrate capping group with hexanethiol should afford some solubility in DCM to the Au NPs.  Repeated attempts at the ligand exchange were unsuccessful as the Au NPs undergo aggregation upon attempted exchange and result in deposition of a thin coating of Au on the glassware.   Ultimately, the method described by Osterloh149 proved successful in yielding large  Au NPs (120 ± 3 nm) soluble in DCM (Figure 3.17a).  In this method, gold salt is reduced in situ by oleylamine, which also serves as a weakly adsorbed capping group.  Oleylamine is then exchanged with the more strongly-coordinating thiol by heating a toluene solution of the Au NPs to reflux in the presence of an excess of hexanethiol.    Once the oleylamine is exchanged, the hexanethiol-capped Au NPs precipitate out of solution as a black powder. 102  PEDOT-Au NP hybrid films were prepared by electrodepositing PEDOT from a monomer solution containing the large Au NPs.  Without an electropolymerizeable group on the Au NPs, the synthesis of the hybrid films is dependent on the Au NPs becoming trapped in the growing PEDOT.  The micrographs of polymer deposited onto a Cu TEM grid show areas of significant Au NP aggregation (Figure 3.17c) as well as μm-sized Au wires (Figure 3.17b).  In addition to the tendency of the Au NPs to form clusters by themselves, EDOT is also known to cause the aggregation of Au NPs.167   Figure 3.17. TEM images of a) large hexanethiol-capped Au NPs and b,c) PEDOT-Au NPs hybrid films showing Au NP aggregation.  3.4 Conclusions.  PEDOT-Au NP films were generated by potentiodynamic deposition from a monomer solution containing both EDOT and 4.  The relative amount Au NPs in the hybrid film can be tuned by altering the relative ratio of the monomers in solution.  Exposing the film to an iodide/triiodide solution lowers the Au content of the film, and TEM images reveal that the Au 103  NPs are etched leaving nm-sized pores in the films.  Type I supercapacitors with the PEDOT-4 films were built and the performance of etched and unetched films were compared.  RC time constants of 0.93 and 0.59 s were measured for the supercapacitor device before and after etching, an improvement of 35%.  The decrease in the RC time constant is attributed to improved ionic conductivity of the films. Attempts to enhance this effect with larger Au NPs were unsuccessful as ripening of the Au NP lowered their solubility.  Large soluble Au NPs capped with hexanethiol aggregate under the conditions required for deposition of PEDOT.   104  Chapter 4   Oligothiophene-capped Copper Nanoparticles 4.1 Introduction. Research into copper nanoparticles (Cu NPs) has been growing steadily over the past 10 years however Cu NPs remain relatively unexplored when compared to other, more-established metal nanoparticles, such as Au NPs.  Interest in these nanoparticles is driven primarily by the high electrical conductivity of bulk copper (60 MS cm-1) 168 and relatively low cost of the metal salt starting materials ($1/g vs. $131/g for CuCl2 and HAuCl4, respectively, from Sigma Aldrich).169  Aside from these considerations, Cu NPs are also attractive as antifungal/antibacterial agents170-176 and as catalysts for a variety of organic synthetic reactions.177-181  However, copper is susceptible to oxidation which can result in the formation of copper oxide NPs during attempted syntheses of Cu(0) NPs. As with Au NPs, in order to minimize their oxidation and aggregation, Cu NPs have been prepared with a variety of capping groups including phosphines,182 alkylthiols,183, 184 tetraalkyl ammonium complexes,185 amines182, 186 and mercaptoalkylthiophene compounds.187         Capping Cu NPs with a polymerizable group is the first step towards polymer-Cu NPs hybrid materials with enhanced properties.  Acrylate monomers have been used to create a Cu NP-embedded polymer for antifouling,173 and photopolymerization of bithiophene-capped Cu NPs has led to a PT-based material with enhanced conductivity.188 The mechanism of photopolymerization involves an electron transfer from the excited bithiophene ligand to the metal core, analogous to what was observed previously for bithiophene-capped Au NPs.189, 190 105   The enhanced conductivity as well as the potential to use the Cu metal core as an electron reservoir makes the integration of Cu NPs in a polymer-based supercapacitor an attractive prospect.  This chapter describes the synthesis and characterization of 1-capped Cu NPs and poly(1-Cu NPs), and the electrochemistry of the polymerized Cu NPs.  4.2 Experimental. 4.2.1 General. Chemicals were purchased from Aldrich, except for EDOT which was a gift from Bayer.  All chemicals were used as received except EDOT, which was distilled prior to use, and [(n-Bu)4N]PF6, which was recrystallized three times from hot EtOH and dried in vacuo at 100 oC for 5 days.  All reactions were performed under an inert N2 atmosphere using standard Schlenk techniques with dry solvents, unless otherwise stated.  Electropolymerization, cyclic voltammetry and galvanostatic charging experiments were performed using a Brinkmann PGSTAT12 Autolab potentiostat.  TEM was performed using a Hitachi H7600 Electron Microscope operating at 100 kV.  Cu NPs were dropcast onto 300-mesh carbon-coated copper grids.  SEM and EDX spectroscopy was performed using a Hitachi S-3000N electron microscope on polymer samples deposited on ITO.  Powder X-ray diffraction (PXRD) was performed using Bruker D8 Advance with a Cu radiation source.  The Cu NP powder was adhered to a glass slide using Comet Vaseline grease.  Polymer samples were first removed from the ITO substrate using a razor blade and then carefully adhered to a glass slide.  TGA was performed using a Perkin-Elmer Pyris 6 TGA.  The temperature was ramped from 30 °C to 900 °C at 10 °C/minute using 4-6 mg of sample.  Emission and excitation spectra were 106  acquired using a PTI Quantamaster spectrometer.  UV-vis absorption spectra were acquired using a Cary-5000 UV-vis-NIR spectrophotometer. XPSPeak software  was used to fit the XPS data.      4.2.2 Synthesis. 3′-thio-2,2′:5′,2′′-terthiophene capped Cu NPs (7). The Cu NPs passivated with 1 were prepared according to a modified single-phase Brust-Schiffrin synthesis (Scheme 4.1).126  To a 0.1 M CuCl2·2H2O aqueous solution (100 ml), a 0.01 M solution of 1 in EtOH (100 ml) was added.  The resulting blue-green solution was sparged with N2 for 8 hours.  To the deaerated solution, 10 ml of a freshly-prepared 1M aqueous solution of sodium borohydride was added at once. A gas immediately evolved along with a colour change from blue-green to brown.  The solution was allowed to stir for 4 hrs at room temperature, and the DCM was removed in vacuo and toluene was added to the remaining EtOH fraction in order to create separate organic and aqueous phases.  The organic layer was extracted and washed repeatedly with deionized water to remove any excess sodium borohydride.  The solvent volume was decreased under reduced pressure and the nanoparticles precipitated out of solution by addition of hexanes.  The nanoparticles were filtered, redissolved in a minimum quantity of DCM, and subsequently precipitated out in hexanes and refiltered.  This process was repeated until the filtrate was clear, indicating the complete removal of any unbound oligothiophene.  At this point, not all the material was soluble in DCM, and the insoluble fraction was separated via filtration using a glass-fritted Buchner funnel.     107  The absence of unbound oligothiophene was further confirmed via 1H NMR spectroscopy of the Cu NPs which showed only broad peaks in the aromatic region corresponding to bound oligothiophene.    4.2.3 Electropolymerization of soluble 7. To a 0.1 M [(n-Bu)4N]ClO4 DCM solution (10 ml), 7 (10 mg) was added to prepare the electrolytic solution.   Polymer samples were prepared from this solution via cyclic voltammetry or potentiostatic deposition.  Glassy carbon electrodes, Ag/AgNO3 (0.01 M) and a platinum mesh were used as the working, reference and counter electrodes, respectively.  Polymer samples were also deposited onto ITO on glass slides for electron microscopic imaging and XPS analysis.  Cyclic voltammetry of the samples was performed in a monomer-free 0.1 M [(n-Bu)4N](PF6) MeCN solution with a platinum mesh counter electrode and a 0.01 M AgNO3 reference electrode, unless otherwise stated.    4.2.4 Co-electropolymerization of EDOT with 7 (PEDOT-7). To a 0.1 M [(n-Bu)4N]PF6 DCM solution (10 ml), 7 (10 mg) and EDOT (0.1 ml) were added to prepare the electrolytic solution.   The copolymers (PEDOT-7) were deposited from this solution potentiostatically at 1 V until 0.25 C of charge had been consumed.  Glassy carbon electrodes, Ag/AgNO3 (0.01 M) and a platinum mesh were used as the working, reference and 108  counter electrodes, respectively.  Pure PEDOT samples were prepared under identical conditions but without added 7.     Cyclic voltammetry of both PEDOT-7 and PEDOT was performed in a monomer-free 0.1 M [(n-Bu)4N](PF6) MeCN solution with a platinum mesh counter electrode and a 0.01 M AgNO3 reference electrode, unless otherwise stated.    4.3 Results and Discussion. 4.3.1 Synthesis of 7.   7 was synthesized according to a modified Brust-Schiffrin synthesis.126  Because DCM and EtOH are miscible, there was no need for addition of a phase transfer agent such as tetraoctylammonium bromide (TOAB).  This simplified the purification steps as this salt is a common contaminant in Brust-Schiffrin syntheses.  The N2 sparging step prior to the NaBH4 reduction is critical to ensure that the copper does not oxidize prior to capping by 1.  After purification, it was found that there were two forms of Cu NPs: 1) a green particle insoluble in DCM and 2) a DCM soluble brown particle.  The two forms of particles were separated and characterized separately.     109  Scheme 4.1.  Synthesis of 7.  4.3.2 Characterization of 7. Average dimensions of the two forms of the Cu NPs were determined using TEM (Figure 4.1).  It was initially postulated that one possible origin of the insoluble fraction could be incomplete capping of the Cu NPs leading to the formation of large, less-soluble agglomerates.  This is clearly not the case as both the images from the insoluble (Figure 4.1a) and soluble (Figure 4.1b) fractions reveal discrete, spherical particles.  The sizes of the particles were calculated using ImageJ.191  The average diameter was calculated from a sample of 85 nanoparticles and is reported with an error of one standard deviation.  The insoluble particles are 10 ± 1 nm in diameter while the soluble particles are 11 ± 2 nm in diameter.   7 110                                                                                                                                                          Figure 4.1.  HR-TEM images of a) the insoluble and b) the soluble fractions separated during synthesis of 7.  The size distribution histograms for the c) insoluble and d) soluble fractions.  The TGA thermal profiles reveal a difference between the two particles which helps explain the difference in their solubilities (Figure 4.2).  Weight loss for the soluble fraction starts at 280 °C and the particles are 23% organic material by weight.  The average number of copper atoms per nanoparticle was calculated using the equation:  20 nm a) 20 nm b) c) d) 111  Equation 4.1.                                        𝐶𝑢 𝑎𝑡𝑜𝑚𝑠 𝑝𝑒𝑟 𝐶𝑢𝑁𝑃 =(1 − 𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑤𝑡%)(𝑀𝑊 𝟏)(𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑤𝑡%)(𝐴𝑤 𝐶𝑢)     Assuming the copper is not oxidized, this amounts to an average of 14 Cu atoms per ligand.  Weight loss for the insoluble fraction starts at 350 °C and the particles are 43% organic material by weight, corresponding to ~6 Cu atoms per ligand.  Since the TEM images indicate the particles are similar in size, and thus should have the same average number of Cu atoms per nanoparticle, the difference in the organic weight percentage means that the NPs in the insoluble fraction have more capping ligands than the NPs in the soluble fraction.  This is counterintuitive as the solubility of nanoparticles is typically controlled by the capping ligands, and the presence of more capping ligands would be expected to impart a higher degree of solubility.   The higher temperature at which weight loss occurs for the insoluble particles, however, suggests that the capping ligands are not the same in both types of particles.  During typical two-phase Brust-Schiffrin synthesis, the phase transfer catalyst TOAB is a common impurity in the resulting nanoparticles as it can act as a capping ligand.  However, TOAB was not used in the synthetic procedure used here and sodium borohydride, used as the reducing agent, is not known to cap nanoparticles.  This leaves only the capping ligand 1 to explain the difference in the weight loss and suggests that 1 may be undergoing a reaction in situ at some point prior to its TGA measurement.  Photoinduced polymerization of bithiophene-capped Cu NPs has been reported previously where polymerization occurs between ligands on adjacent Cu NPs.192   If the solution of Cu NPs is sufficiently dilute, polymerization could occur between adjacent 112  ligands surrounding a single particle (intraparticle) and not between ligands on separate particles (interparticle).  Intraparticle polymerization has been used to prepare PT-capped Au NPs.130  Photoinduced intraparticle polymerization of 1 would result in particles of lower solubility and with increased thermal stability.  This would explain the distinct particles observed in the TEM images, as opposed to aggregations of particles, and the higher thermal stability for the particles in the insoluble fraction.  The greater number of capping ligands on the insoluble fraction would lead to a decreased distance between each ligand and facilitate intraparticle polymerization.   Figure 4.2.  TGA thermal profiles of soluble (blue trace) and insoluble (red trace) fractions of 7.          To test the possibility that photopolymerization is leading to the differences between the two fractions, a solution of the soluble Cu NPs was prepared in DCM and the UV-vis spectrum 113  was acquired before and after irradiation at 365 nm using a hand-held UV lamp (Figure 4.1).  A redshift of 15 nm is observed in the π*←π absorption band after 90 minutes of irradiation, consistent with an increase in conjugation from polymerization of the capping ligand.     Figure 4.3.  UV-vis spectra of 7 before and after irradiation at 365 nm.   To further verify the photopolymerizability of 7, the fluorescence emission and excitation spectra of the Cu NPs were recorded (Figure 4.4).  An Ar-sparged solution of the soluble Cu NPs was prepared in MeCN to an optical density of 0.1.  The emission spectrum when excited at 340 nm (directly into the π⃰←π absorption band) was recorded showing an intense violet emission at 435 nm.  The excitation spectrum at 440 nm was recorded, which matches the absorbance spectrum of 7 in Figure 4.3, verifying that the emission observed at 435 nm is not an impurity present in low quantity.   114  To initiate photopolymerization, the solution was irradiated in the fluorimeter at 340 nm for 15 minutes.  The emission and excitation spectra were then re-recorded after irradiation.  When excited at 340 nm, the irradiated sample has diminished emission intensity at 435 nm and a new emission peak appears at 610 nm.  A new emission peak at lower energy is consistent with an increase in conjugation length of the emitting species.  The shape of the excitation spectrum at 440 nm is similar before and after irradiation but lower in intensity.     Figure 4.4.  Fluorescence emission (λex = 340 nm) and excitation (λem = 440 nm) spectra for soluble 7 before and after irradiation at 340 nm for 15 mins.  The emission at 610 nm was then probed to see if it originates from the same species in solution.  The excitation spectrum collected at 610 nm shows a peak at 440 nm (Figure 4.5), with little contribution from the absorbance at 340 nm.  This suggests that the species 115  responsible for the emission band at 435 nm, Cu-bound 1, is not responsible for the emission at 610 nm.  The emission at 610 nm must originate from longer oligomers of 1.  This is consistent with photopolymerization of the Cu-bound 1 and may explain the formation of the insoluble Cu NPs.  For this reason, care should be taken to avoid exposing the Cu NPs to light during their synthesis.                 Figure 4.5.  Excitation spectra of 7 post irradiation monitored at 440 nm and 610 nm.  At this point, work with the insoluble fraction from 7 ceased.  All further mentions of 7 refer to the soluble fraction unless otherwise stated.   116  4.3.3 Electropolymerization of 7. The electrochemistry of 7 was explored using cyclic voltammetry.  It was hoped that the particles could be electropolymerized in a similar fashion as the Au NPs.  Also the enhanced conductivity of Cu vs. Au (60 and 43 MS cm-1, respectively)168 might lead to improved properties of the film, such as a cathodic shift of the oxidation potential of 7 from that of 4.  DCM was chosen as the solvent based on its ability to dissolve the Cu NPs.  The initial scan from 0 V to 1 V showed a first oxidation peak around 0.9 V, assigned to oxidation of the capping terthiophene ligand (Figure 4.6 red line).  The reverse scan from 1 V to -1 V showed two reduction features, one at 0.5 V and the second at -0.2 V.  Cycling repeatedly between -1 V and 1 V showed the characteristic increase in current expected for electropolymerization as well as three new oxidation peaks at 0.25 V, 0.5 V and 0.8 V (Figure 4.6).  The peak at 0.8 V is assigned to the oxidation of the polymer.  The two other oxidation peaks at the lower potentials are possibly from copper oxidation processes occurring during the electropolymerization.  When an ITO substrate was used, the poly(7) film had a very thin, dark-red/brown colour.  Thicker films are achievable by cycling up to 1.5 V but the voltammograms show evidence of film degradation.  Films grown at the higher potential are more brown in appearance than those grown by cycling to 1 V.  117   Figure 4.6.  Electropolymerization of 7 by CV onto a glassy carbon electrode.  Red line designates the initial scan and blue lines are the subsequent scans.    In order to enhance the quality of the films, polymer samples were prepared by potentiostatic deposition of 7 at 0.8 V for 1 hour.  The poly(7) films prepared by this method had a more reddish hue than those prepared by cyclic voltammetry and were of suitable thickness for further characterization.  4.3.4 Characterization of Poly(7). Poly(7) was characterized by PXRD by removing the polymer from the substrate using a razor blade and mounting onto a glass slide with Comet 117  grease as an adhesive.  Removing the films from the ITO was done in order to eliminate diffraction from the ITO 118  surface which might complicate the observed diffraction pattern.  Poly(7) films grown at 0.8 V had a powder XRD pattern matching face-centred cubic copper (0) lines (Figure 4.7a).  The peaks at 43.2°, 50.3°, and 73.9° correspond to the (111), (200), and (220) crystal planes.  This was somewhat surprising as a film of unpolymerized 7 did not show diffraction patterns (Figure A.3).  The poly(7) films grown at 1.2 V did not display any peaks matching those for Cu(0) or any other copper species nor those for crystalline polythiophene (Figure 4.7b).  The peaks that are observed are thus assigned to crystallites of the electrolyte, [(n-Bu)4N]ClO4.    The origin of Cu peaks in the polymer sample that are not observed in the unpolymerized Cu nanoparticles has to do with crystalline size.  The size of the crystals is inversely proportional to the width of the diffraction peak according to the Debye-Scherrer equation:  Equation 4.2.                                        𝐷 =0.9𝜆𝛽𝑐𝑜𝑠𝜃     where D is the crystallite size, λ is the wavelength of the X-ray source (0.154 nm for Cu), β is the FWHM for the diffraction peak and θ is the diffraction angle.  Using the (111) diffraction peak at 2θ = 43o, the calculated crystallite size from the polymer sample is 44 nm.  This is much larger than the individual nanoparticles, which are 11 nm in diameter.  This suggests that the particles in the polymer sample are ordered in a crystalline regime.  The Debye-Scherrer equation also explains why the XRD from the dropcast nanoparticle sample is not observed.  The nanoparticle diameter is 11 nm, which corresponds to a FWHM of 2θ = 0.01o, too broad a signal to be observed above the baseline.    119   Figure 4.7.  PXRD for poly(7) grown at a) 0.8 V and b) 1.2 V.  a) b) (111) (200) (220) 120  The poly(7) films were analyzed using SEM-EDX to examine the differences between films grown under two different conditions (0.8 V and 1.2 V).  Poly(7) grown at 0.8 V (Figure 4.8) shows areas of microcrystallinity consistent with what is observed using PXRD.  In contrast, poly(7) films grown at 1.2 V (Figure 4.9) are amorphous and have a porous, fibrillar morphology.  A similar change in the morphology based on the deposition potential has been observed for PEDOT.47  The lower potential leads to a slower rate of electropolymerization and deposition of polymer and allows for structural reordering of the film into crystalline regions.  At higher anodic potentials, the deposition rate is high and does not result in the formation of crystalline regions.  Overpotential oxidation and degradation of the polymer film also occurs at higher potentials.  Because of this, all further poly(7) films were deposited at 0.8 V unless stated otherwise.   121   Figure 4.8.  SEM images of poly(7) grown at 0.8 V.  Lines were added to highlight areas of microcrystallinity.  Part b) is a higher magnification image of the area enclosed in the box in part a).  a) b) 122   Figure 4.9.  SEM images of poly(7) grown at 1.2 V.   The image in b) is a magnified version of the area enclosed in the box in a).  a)  b) 123  The EDX spectra of a poly(7) film deposited at 0.8 V is presented in Figure 4.10.  Again, peaks from the ITO substrate dominate the spectrum.   The remaining peaks are assigned to Cu and S atoms originating from 7.  The S : Cu atomic ratio calculated from fitting the peaks in the spectrum is 3 : 1 (Table 4.1).        Figure 4.10.  EDX spectra for poly(7).  The XPS spectrum of poly(7) also confirmed the presence of the Cu atoms in the polymer film (Figure 4.11a).  The S : Cu ratio calculated from the XPS spectrum is 9 : 1, inconsistent with the results obtained by EDX.  XPS is highly surface sensitive and atomic ratios derived from these results may not be representative of the bulk composition.  The summary of the elemental analyses for both 7 and poly(7) is shown in Table 4.1. Si In Sn Sn In S Cu 124  The Cu : 1 ratio is representative of the number of capping ligands around the Cu NP core.  The TGA and XPS analysis of the unpolymerized 7 are consistent with each other, with 14 Cu atoms per capping ligand.  The number of Cu atoms per ligand decreases significantly upon polymerization, to 1.3 or 0.4 Cu atoms per ligand when measured by XPS or EDX, respectively.  This constitutes a stark decrease in the relative number of Cu atoms upon polymerization.  One possible explanation is the presence of unbound 1 in the electrolytic solution, which polymerizes preferentially over 7.  The 1H NMR spectrum of 7 did not show any evidence of free 1, but it is possible that the ligand can become labile under the electropolymerization conditions.  Ligand substitution with the tetrabutyl ammonium cation could lead to free 1.  Table 4.1.  Comparison of the atomic composition of 7 and poly(7) . Sample Method S : Cu 1 : Cu 7 XPS 1 : 3.65 1 : 15 7 TGA 1 : 3.5 1 : 14 Poly(7) XPS 1 : 0.1 1 : 0.4 Poly(7) EDX 1 : 0.33 1 : 1.3  Along with elemental analysis, the Cu 2p XPS spectra provide further information about the oxidation state of the Cu atoms in the particles (Figure 4.11b).  Peaks in the spectra originate from both Cu(0) 2p1/2 and 2p3/2 states (at 953 eV and 933 eV, respectively) and Cu(II) 2p1/2 and 2p3/2 states (at 955 eV and 935 eV, respectively).  The two remaining peaks at 963 eV and 944 eV are shake-up satellites, characteristic of Cu(II).  CuS species from the surface Cu atoms as well as CuO from oxidation of surface atoms could account for the presence of 125  Cu(II).  However, satellite peaks are not observed for CuS species because of electron-orbital interactions,193  which suggests that oxidation of the surface of the Cu is occuring.  Because XPS analysis is limited to probing the surface of the species, it is unclear if the Cu NPs in the bulk of the polymer are as oxidized as those exposed at the surface.     Fitting and integration of the peaks indicates the the surface of the polymer consists of 85% CuO and 15% Cu(0).   126   Figure 4.11.  a) Full scan and b) Cu 2p XPS spectra of poly(7).    Cu 2p Cu 2p O 1s Cu LMM C 1s S 2s S 2p Cu 3p 127  4.3.5 Electrochemistry of Poly(7). The electrochemistry of the poly(7)-modified GCE electrodes was studied in a three-electrode set-up in a 0.l M [(n-Bu)4N]PF6 MeCN solution.  Initially, the scan rate was set at 100 mV s-1 (Figure 4.12a).  During the first scan (red trace), an increase in current consistent with p-doping of the polymer is observed starting at 0.4 V.  In the reverse direction, a reduction wave is observed at 0.7 V from dedoping of the polymer.  No n-doping is observed for this polymer even when the potential is scanned as far negative as -2 V.  Subsequent scans (blue traces) have a similar shape to the first scan but with slight differences.  Scanning in the positive direction, an anodic peak is observed at 0.75 V and the current reaches a lower maximum than in the initial scan.  Scanning in the reverse direction, the current changes faster than in the initial scan.  The appearance of the anodic peak and the faster current change upon reversal of scanning direction suggest improved charging/discharging kinetics of the polymer. This is not an uncommon observation and is usually ascribed to the first scan being used to “condition” the polymer, involving the flow of ions and solvent into and out of the polymer.42, 194, 195  The anodic peak at 0.75 V can be more clearly seen at slower scan rates, i.e. 5 mV s-1 (Figure 4.12b).   After the initial scan, the polymer showed little change in its voltammogram over repeated scans, provided the potential does not exceed 1 V.  The sharp rise in the current at around 1 V is possibly a parasitic reaction involving the solvent or electrolyte or irreversible oxidation of the polymer film.  The film as observed when deposited onto ITO is electrochromic going from a red colour in the undoped state to a black colour upon doping.  When the scanning potential exceeds 1 V, the polymer becomes a brown colour and is no longer electrochromic.              128  A plot of the current normalized by the scan rate is shown in Figure 4.12d.  For surface-bound species, such as the PEDOT-7 modified electrodes, a linear relationship between current and sweep rate is expected.  Normalizing the current from the CV by the sweep rate, the normalized CV plots at the different scan rates should overlap.  At scan rates greater than 100 mV s-1, there is a sharp drop in the normalized current, and the charging of the polymer becomes non-ideal.  This can be seen clearly in a plot of the cathodic peak current against the sweep rate.  Deviations from linearity start at sweep rates of 100 mVs-1 and greater.  The deviation from linearity is often attributed to the doping/dedoping of the polymer becoming limited by ion diffusion.  At scan rates slower than 100 mV s-1, the Faradaic electron transfer from the electrode to the polymer limits the doping rate. 129    Figure 4.12.  CVs of poly(7) in 0.1 M [(n-Bu)4N]PF6 in MeCN at a) 100 mV s-1 , b) 5 mV s-1 and c) 1 V s-1.  Plot d) is the current for each scan normalized by the sweep rate and e) is the plot of peak current against sweep rate.   a) b) c) e) d) 130  4.3.6 PEDOT-7 Copolymers. To further examine the effects of the presence of Cu NPs on the electrochemistry of PT, a Cu NP-embedded PEDOT film (PEDOT-7) was deposited.  It has been shown previously that a blend of PEDOT/polystyrene sulfonate mixed with Cu NPs exhibits enhanced conductivity relative to the native polymer mixture (no Cu NPs).196  PEDOT-7 films were deposited by coelectropolymerizing EDOT in the presence of a relatively small amount of Cu NPs (Figure 4.13).     Figure 4.13.  TEM image of PEDOT-7 film.  By keeping the relative amount of 7 low, the majority of the electroactivity should still originate from the PEDOT. In order to compare to PEDOT-7, pure PEDOT was deposited 20 nm 131  under identical conditions as PEDOT-7.  This comparison helps elucidate any effect the Cu NPs would have on the PEDOT films.  The resulting polymers were analyzed using cyclic voltammetry in a 0.1 M n-[(C4H9)4N]PF6  MeCN solution (Figure 4.14).    Figure 4.14.  CVs of PEDOT (blue trace) and PEDOT-7 (red trace) at a,b) 2 mV s-1, c,d) 10 mV s-1 and e,f) 50 mV s-1.  a) c) e) f) b) d) 132  The general shape of the voltammograms are typical of those for PEDOT, however, there are some clear differences with the addition of just a small amount of 7.  The capacitance of the PEDOT-7 films is higher than for PEDOT.  This is most obvious at slower scan rates, as seen in Figure 4.14b.  In Figure 4.14a, a wider potential window is scanned and the PEDOT p-doping peak can be observed and compared.  There is a 30 mV cathodic shift in the p-doping peak in the PEDOT-7 films (from -0.16 V to -0.19 V).  The dedoping peak in the reverse scan at -0.7 V is also sharper.  The capacitance for the PEDOT-7 films were calculated from the average current during the forward scan from -0.5 to 0.5 V using Equation 1.4.  For both the PEDOT and PEDOT-7 films, the capacitance of the polymer decreases significantly at scan rates of 25 mV s-1 and higher (Figure 4.15).  The cause of this decrease is typically assigned to diffusion-limited charging.197, 198  That both the PEDOT and PEDOT-7 decrease at the same scan rate suggests that the ionic conductivity of PEDOT is unchanged by the presence of Cu NPs, and the differences observed in the voltammograms are primarily electronic in nature.  This appears to also be the case here, as the improved conductivity from the Cu NPs accounting primarily for the changes observed in the voltammograms.  133   Figure 4.15.  Effect of scan rate on capacitance of PEDOT (red data points) and PEDOT-7 (blue data points).  4.4 Conclusions. Cu NPs bound with the electropolymerizeable oligothiophene group 1 were synthesized.  It was observed that two different types of Cu NPs were produced during the synthesis, a soluble and insoluble fraction.  It was speculated that the insoluble fraction was a result of photopolymerization of 1 during the synthesis, and this hypothesis was reinforced with both TGA data and photolysis experiments.  The soluble Cu NP fraction was successfully electropolymerized at a lower oxidative potential than the Au NP analogues, which allowed for the formation of crystalline regions in the polymer.  The poly(7) film was electrochromic and exhibited good charging and discharging kinetics up to 100 mV s-1.  PEDOT co-polymerized with the Cu NPs showed improved capacitance over native PEDOT films, owing 134  to the improved conductivity afforded by the Cu NPs.  These results suggest that Cu NPs can be a cheap and attractive additive to conducting polymers to improve their conductivity.     135  Chapter 5 Azidothiophene Compounds for  Polymer Crosslinking  5.1 Introduction. During the course of doping of PT, the polymer’s free volume can increase by 25%199 due to the incorporation of counterions and solvent molecules200 as well as structural rearrangement of the polymer.201  While this can be used advantageously to create actuators,202-204 the mechanical stress of repetitive volume changes are a detriment to the cycling ability of polymer supercapacitors (10 000 cycles)87, 205 compared to HSAC supercapacitors (500 000 - 1 000 000 cycles).88, 89  One approach to addressing this issue described in this chapter is to crosslink the polymer in its doped, porous state (Scheme 5.1).  This is anticipated to both minimize the volume changes and improve the ion mobility in the polymer during doping.  It has been shown that porous polymer has a higher ion mobility and hence conductivity than dense polymer.119  Though changes in volume are not addressed in this chapter, the effect of crosslinking on the ionic mobility and the discharging kinetics of the polymer is explored.  136  Scheme 5.1.  Effect of doping/dedoping on volume of a polymer film before and after cross-linking.  Azido functional groups are commonly used as a cross-linking agent in polymer chemistry, particularly as a resist in photolithography.206  Much of their rich chemistry owes to the highly reactive nitrene group formed upon either thermo- or photolysis of the azide moiety (Scheme 5.2).207    Scheme 5.2.  Thermolysis or Photolysis of an Azide.   The nitrene can undergo many reactions to crosslink the polymer, including inserting itself into C-H single and double bonds or combining with another nitrene group on an opposing polymer strand.  Post-polymerization thermal cross-linking of PMMA with sulfonyl azide side groups208 and benzylazide groups209 has previously been carried out in order to enhance the robustness of the polymer.  This crosslinking strategy has also been applied to PT.  137  Thermolysis of an alkyl azide substituted PT was used to crosslink the polymer, which led to a shorter average conjugation length but improved mechanical strength of the polymer.210, 211   While thermolysis of alkyl azides is common, photolysis of alkyl azides is inefficient because of their low molar absorptivity (ɛ ~25 M-1 cm-1) at short wavelengths (286 - 288 nm).212  To circumvent this issue, aryl azides may be used allowing for irradiation into the absorbance band of the aryl unit which then undergoes energy transfer to the azide.213  The photochemistry of aryl azides was first explored by Wolff in 1912.214  In this chemistry, the product of irradiation is often intractable tar due to the myriad of reactions that the nitrene can undergo.215-218  More recently, irradiation of phenyl azides has been used as a strategy to form conducting polymers.219  Aside from azides, bromo groups have been added to the side chain of thiophene in order to photocrosslink after polymerization.  This was done with an eye towards the application in photovoltaics.220 In most cases, only a low degree of crosslinking of the polymer is required for optimal properties.  For example, enhanced conductivity of PEDOT was observed when copolymerized with 0.5 - 2 mole % of a conjugated crosslinking agent.211      This chapter describes the synthesis of an azidostyrylthiophene compound.  Its thermo- and photochemical reactions are probed and compared to a styrylthiophene control compound.  The electrochemical behaviour of the azidostyrylthiophene on its own and its use as a cross-linking agent when copolymerized in PEDOT is explored.                                   138  5.2 Experimental. 5.2.1 General. Chemicals were purchased from Aldrich, except for EDOT which was a gift from Bayer.  All chemicals were used as received except EDOT, which was distilled prior to use, and [(n-Bu)4N]PF6 and [(n-Bu)4N]BF4, which were recrystallized three times from hot EtOH and dried in vacuo at 100 oC for 5 days.  All reactions were performed under an inert N2 atmosphere using standard Schlenk techniques with dry solvents, unless otherwise stated.  Electropolymerization, cyclic voltammetry and galvanostatic charging experiments were performed using a Brinkmann PGSTAT12 Autolab potentiostat.  TGA was performed using a Perkin-Elmer Pyris 6 TGA.  The temperature was ramped from 30 °C to 900 °C at 10 °C/minute using 4-6 mg of sample.  UV-vis absorption spectra were acquired using a Cary-5000 UV-vis-NIR spectrophotometer.  FTIR spectra were acquired using a Nicolet 6700 FTIR spectrometer fitted with a Thermo Scientific Smart Orbit ATR (attenuated total reflectance) accessory.  Synthesis of 4-azidobenzaldehyde followed the procedure of Schuster et al.221  The synthesis of 3-methylphosphonatethiophene and (E)-3-styrylthiophene (8) followed the procedures of Officer et al.222-225     139  5.2.2 Synthesis. (E)-3-4-azidostyrylthiophene (9). A 250 ml round bottom flask was charged with 3-methylphosphonatethiophene (1.13 g, 4.82 mmol) and 4-azidobenzaldehyde (0.79 g, 5.36 mmol) and placed under a N2 atmosphere.  Dry THF (50 ml) was added to the flask and the yellow solution was stirred at room temperature.  The flask was covered in aluminum foil to prevent photodegradation of the reactants and products.  Potassium tert-butoxide (1.11 g, 9.90 mmol) was added to the flask, which caused an instantaneous colour change to dark brown.  After 4 hours, the reaction was quenched first with H2O (25 ml), which resulted in the solution turning red in colour, and then with 1 M HCl (25 ml).  Diethyl ether (50 ml) was added to the solution and the organic layer was separated.  The organic layer was washed three times with deionized H2O (50 ml), dried over MgSO4, and then filtered.  The solvent was removed under reduced pressure to yield a dark red solid.  The product was purified on a silica column using a 9/1 (v/v) hexanes : acetone solvent to yield an 1.05 g (78.6 %) of off-white solid.  Rf = 0.44. 1H NMR (300 MHz, CDCl3): δ, 6.916 (d, J = 16.2, 1 H), 7.016 (d, J = 8.4, 2 H), 7.088 (d, J = 16.2, 1 H), 7.280 (s, 1 H), 7.31-7.37 (m, 2 H), 7.469 (d, J = 8.4). LRMS (EI) Calcd for C12H9N3S (m/z): 227.05; Found: 199 (100%, M-N2), 227 (40%). Anal. C12H9N3S requires C, 63.48; H, 4.00; N, 18.50. Found C, 63.62; H, 3.88; N, 18.67%.         5.2.3 Solution Photolysis of 9. A solution of 9 in HPLC-grade MeCN was prepared in a UV-vis cuvette to a concentration where the optical density of the compound is approximately equal to 1.  The 140  solution was sparged with N2 for 20 minutes, after which time the cuvette was sealed using a rubber stopper and a generous amount of Parafilm laboratory film.  A UV-vis spectrum was acquired before irradiation.  A handhelp UV lamp with a 365 nm bulb was used to irradiate the sample at a distance of 5 cm.  Its irradiance was measured using a Thorlab handheld digital power meter at a distance of 5 cm to be 3 mW cm-2.   In order to characterize the major product of photolysis, 9 (4 mg) was dissolved in MeCN (400 ml) in a 500 ml quartz flat-bottom flask, which resulted in an optical density of 9 of ~1.  The solution was sparged with N2 for 30 mins and subsequently stirred and irradiated in a UV reaction chamber at 365 nm.  Its irradiance was measured using a Thorlab handheld digital power meter in the center of the chamber to be 10 mW cm-2.The photolysis was followed by periodically acquiring the UV-vis spectra of aliquots drawn from solution.  The reaction was complete in 1 hr.  The solvent was then removed under reduced pressure using a rotary evaporator to yield a red solid.       5.2.4 Solid-state Photolysis of 9. A thin film of 9 was deposited onto a float glass substrate by dropcasting from a concentrated solution of the compound in DCM.  The sample was irradiated in a UV reaction chamber using 365 nm bulbs.  The UV-vis spectrum of the thin film of 9 was acquired before and after specific time intervals of irradiation.  After irradiation, 9 was redissolved by rinsing the float glass with HPLC-grade CH3CN.  The solution was then diluted until it reached an approximate optical density of ~1 and a UV-vis spectrum was acquired.   141  In order to acquire a satisfactory IR spectrum, 9 was dropcast directly onto the FT-IR diamond crystal from a concentrated solution in DCM.  The entire ATR accessory was then removed from the FT-IR spectrometer and placed in a UV reaction chamber fitted with 365 nm bulbs.  After irradiation, the ATR accessory was reattached to the spectrometer and the FT-IR spectrum of 9 post-irradiation was acquired.  5.2.5 Electrochemistry of 9. The initial electrochemical characterization of 9 was performed in a 10 mM 9 DCM solution containing 0.1 M [(n-Bu)4N]PF6 (10 ml).  A platinum button electrode, Ag wire and a platinum mesh were used as the working, pseudoreference and counter electrodes, respectively.   Subsequent cyclic voltammograms of 9 were performed in a 10 mM 9 CH3CN solution containing 0.1 M [(n-Bu)4N]PF6  (10 ml). A 1mm diameter platinum button electrode, Ag/AgNO3 (0.01 M) and a platinum mesh were used as the working, reference and counter electrodes, respectively.  BF3-OEt2  (0.05 ml) was added to the solution and the working electrode was removed from solution, wiped with a Kimtech precision wipe, returned to the electrolyte and the CV was then rerun under identical conditions.  This procedure was repeated again with additional BF3-OEt2  (0.05 ml) added .       142  5.2.6 Co-polymerization of 9 and EDOT. A solution of 0.1 M [(n-Bu)4N]PF6, 0.02 M EDOT in DCM (200 ml) was prepared and stored in a Schlenk flask.  The solution was degassed via three freeze-pump-thaw cycles.  A 10 ml aliquot of the solution was transferred to the electrochemical cell to be used as the electrolytic solution.  Either a glassy carbon electrode or indium tin oxide on float glass was used as the working electrode.    Ag/AgNO3 (0.01 M) and a platinum mesh were used as the reference and working electrodes, respectively.  PEDOT was deposited potentiostatically at 1.7 V until a charge of 0.25 C had passed.  To the electrolytic solution, 9 (10 mg) was added and the PEDOT-9 co-polymer was deposited at 1.7 V until a charge of 0.25 C has passed.    5.2.7 Electrochemical Testing of PEDOT-9 Copolymer. The PEDOT and PEDOT-9 polymers were tested in monomer-free solution of 0.1 M [(n-Bu)4N]PF6 in CH3CN using a Ag/AgNO3 (0.01 M) and a platinum mesh were used as the reference and counter electrodes, respectively.   Type I supercapacitors were built with the polymer-modified ITO electrodes.  Before assembly, the electrodes used as the cathode and anode were held potentiostatically at 1 V and -1 V, respectively.  Conductive tape was added to the end of each electrode to improve contact between the potentiostat leads and the electrode.  The Celgard separator was soaked in the electrolytic solution and the device was held together with conventional binder clips. Irradiation of the electrodes was performed through the back-side of the device using the UV reaction chamber fitted with 365 nm lamps (Figure 5.1).  143                           Figure 5.1. Irradiation of an assembled device.  5.3 Results. 5.3.1 Synthesis of 8 and 9. The arylazide group was selected as the functional group for photo-induced crosslinking.  The styryl bridge unit connecting the thiophene and the azide extends the crosslinking group further away from the main chain of the polymer and provides greater rigidity than an alkyl group.   Despite the low purity reported in the literature method,221 4-azidobenzaldehyde was synthesized as 99% pure by the 1H NMR spectrum after column chromatography and recrystallization (Scheme 5.3).  The FT-IR spectrum of 4-azidobenzaldehyde showed the characteristically strong azide stretching peak at 2120 cm-1.         Electrode Electrode Polymer Polymer Separator hν 144  Scheme 5.3. Synthesis of 4-azidobenzaldehyde.   The synthetic route to both 9 and its hydrocarbon parent compound 8 are identical until the final step (Scheme 5.4).  In the first step, 3-methoxythiophene is converted to 3-methylbromothiophene.  A Michaelis-Arbuzov reaction was then performed to yield the 3-methylphosphonate-thiophene.  The phosphonate was used as a platform to yield both 8 and 9 via a Horner-Wadsworth-Emmons reaction with either benzaldehyde or 4-azidobenzaldehyde, respectively.  The Horner-Wadsworth-Emmons reaction is selective for the trans product.  The trans product is also what was obtained from the literature synthesis of styrylthiophene.225  The J coupling of the vinyl protons of 9 was 16.2 Hz, which is consistent with trans product.  All reactions had moderate yields, and were not optimized. The FT-IR spectrum of 9 showed the characteristic azide stretch at 2130 cm-1.  Because of thermal and photo-degradation, 9 was stored in an vial wrapped in aluminum foil in the refrigerator.      145  Scheme 5.4.  Synthetic Pathway to 8 and 9.   5.3.2 Thermogravimetric Analysis of 8 and 9. The thermal profile of 8 and 9 were investigated using TGA (Figure 5.2).  A single major weight loss step at 198 °C was observed for 8.  Weight loss for 9 begins at 157 °C, a typical temperature for the thermolysis of aromatic azides.  There is a 15 % weight loss during the first step, consistent with the theoretical 12 % weight loss calculated for the thermolysis and release of N2 from 9 (Equation 5.1). Equation 5.1 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 𝑙𝑜𝑠𝑠 =𝑀𝑊 𝑜𝑓 𝑁2𝑀𝑊 𝑜𝑓 𝟗=28.01𝑔𝑚𝑜𝑙−1227.29 𝑔𝑚𝑜𝑙−1= 12.32% 146  Beyond the initial step, there are weight loss steps at 245°C and 550 °C.  The greater thermal stability of 9 versus 8 is consistent with cross-linking of 9 after the thermolysis during the initial weight loss.   Figure 5.2.  TGA thermal profile of 8 (blue trace) and 9 (red trace).  When 9 was heated and held at 160 °C for 30 minutes, a hardened black insoluble solid remains.  This solid was ground up in a mortar and pestle and analyzed using IR spectroscopy, showing the complete loss of the azide stretch at 2120 cm-1.  This suggests that thermolysis of 9 at 160 °C results in complete conversion of the azide to the nitrene, which subsequently leads to a highly-crosslinked solid.     8 9 147  5.3.3 Solution Photolysis of 8 and 9. With strong evidence for thermal cross-linking in hand, the effect of photolysis on 9 was investigated.  The UV-vis spectra for 8 and 9 in MeCN are shown in Figure 5.3a.  A bathochromic shift is observed in the absorption spectrum of 9 relative to 8.  This is typical for aromatic azides relative to their parent hydrocarbons.226     Figure 5.3.  a) UV-vis spectra of 8 and 9 in MeCN and b) UV-vis spectra of 9 with increasing photolysis time.  Irradiating the solution of 9 with 365 nm light using a handheld lamp caused dramatic changes in the UV-vis spectra (Figure 5.3b). After just 1 minute of irradiation, the two absorbance bands at 320 nm decrease dramatically in intensity.  A new, lower-energy absorbance band at 405 nm emerges.  This change in the UV-vis spectrum is reflected in a yellowing of the initially clear solution.  The isosbestic point at 350 nm (denoted by the red circle in Figure 5.3b) suggests a clean conversion from 9 to another species.  It is important to a) b)    8    9 148  note that very little change in the UV-vis spectrum was noted for similar irradiation experiments with 8.  Styrylthiophenes can undergo cis-trans rearrangements and photocyclization upon irradiation in certain solvents225, 227, 228 but this was not observed under the conditions used in this experiment.  Initial attempts to characterize the photolysis product of 9 were performed in a quartz NMR tube in MeCN.  The 1H NMR spectrum showed very little change with irradiation despite the solution changing colour and an orange insoluble material depositing on the inside of the NMR tube.  It was speculated that the typical concentration of 9 needed to acquire a 1H NMR spectrum was too high for the irradiation experiment because of the inner filter effect.  In order to alleviate self-filtering, a dilute sample of 9 in MeCN was prepared to the same optical density as that used in the initial irradiation experiment.  During the course of the irradiation, the solution changed from colourless to yellow.  Aliquots were drawn and the initial and final UV-vis spectrum of the solution matched that of the initial irradiation experiments.  When dried, the product of the irradiation was red in colour.  Column chromatography showed, however, that the new absorbance band at 405 nm is due to a minor product (<1 mg) that was not further characterized.  The major product was a brown solid that has a single broad peak in the aromatic region of the 1H NMR spectrum.  Mass spectrometry shows several higher molecular weight peaks suggesting the photoproduct consists of various dimers and oligomers     5.3.4 Solid State Photolysis of 9. Solid state photolysis of 9 was investigated by depositing a thin layer of 9 from solution onto float glass and irradiating the sample at 365 nm using a handheld UV lamp.  UV-vis 149  spectra of the film were acquired at various time intervals (Figure 5.4a).  An increase in the absorption at 440 nm is observed even after 1 minute of irradiation and the emergence of an absorbance band at 330 nm.  After an hour of irradiation, the film was redissolved in MeCN and a solution UV-vis spectrum was acquired (red trace in Figure 5.4b).  The redissolved sample (red trace) has an absorbance band at 420 nm, which matches with the absorbance band that is observed during the solution state irradiation (Figure 5.4b blue trace).  The original absorbance bands at 330 nm are also still present as in the solution before irradiation (Figure 5.4b black trace).  This suggests that the reactions in the solid state are the same as those in solution.  In the solid state, however, there remains a significant degree of unreacted material as the light cannot penetrate through the full depth of the film.    Figure 5.4.  a) Solid-state UV-vis spectra of irradiated 9 and b) UV-vis solution of dissolved irradiated 9.  The photolysis of the azide group was further confirmed by monitoring the FT-IR spectra of a sample of the solid during irradiation (Figure 5.5).  A thin film of 9 was deposited from a 150  DCM solution directly onto the quartz crystal and was irradiated in a UV chamber.  A difference spectrum is presented in the Appendix (Figure A.4).  The intensity of the azide stretch at 2130 cm-1 was significantly diminished after irradiation, which is a clear indication that the azide has undergone photolysis, most likely to the reactive nitrene group.  The IR peaks due to alkene =C-H out-of-plane deformation vibrations at 960 cm-1 and 970 cm-1 are also weaker after irradiaton.  The peaks originating from the benzene ring at 1295 cm-1 and 1315 cm-1 (benzene ring system in-plane vibrations), at 815 cm-1 (benzene C-H stretch), at 770 cm-1 (benzene C-H bending), and the peaks centered around 670 cm-1 (C-H out-of-plane bending) are all weaker after irradiation.  The peak at 1500 cm-1 can be assigned to thiophene in-plane ring stretches and is also diminished after irradiation.  Decrease in intensity after irradiation for suggests that nitrene reacts at these positions during crosslinking.  Interestingly, the peak at 1600 cm-1, which originates from the asymmetric stretch of the alkene linker,229 exhibits very little change in its intensity after irradiation.  The lack of emergence of new peaks is most likely due to the small penetration depth of the irradiation.  Also, ATR FT-IR has a penetration depth of 0.5-2 µm into the material.  The thickness of the dropcast film is not known, however, it is possible that the top surface of the film is not probed by ATR FT-IR.  This top surface would also be exposed to the highest irradiance of light and so the results in Figure 5.5 represent the minimum change in the IR absorbance of the whole film. 151   Figure 5.5.  FT-IR spectra of 9 before (black trace) and after (red trace) irradiation.  5.3.5 Electrochemistry of 8 and 9. The CV of 9 in a 0.1 M [n-(Bu)4N]PF6 DCM solution is presented in Figure 5.6.  In the initial scan (blue trace), an irreversible oxidation peak at 1.2 V and a broad oxidation peak at 1.7 V are observed.  There is a decrease in current upon subsequent scans, suggesting that an insulating film forms on the electrode.  This is consistent with previous work with styrylthiophenes, where electrochemical oxidation resulted in polymer films of low conductivity (10-6 S cm-1).230, 231  The low conductivity of the films was attributed to the oxidation of the alkene linker at a potential lower than that of oxidation of the thiophene ring, which results in a highly crosslinked and non-conjugated polymer.  This was further supported by DFT calculations that showed significant spin density at both the para position of the phenyl ring and at both carbons of the alkene bridge.232   νN3 152    Figure 5.6.  CV of 9 in 0.1 M [(n-Bu)4N]PF6 DCM.  Thiophene that is electropolymerized in the solvated Lewis acid BF3-OEt2 has been shown to form PT of high conductivity (1300 S cm-1) and tensile strength.233, 234  This was attributed to the lowering of the oxidation potential of thiophene by dearomatization of the thiophene ring by coordination of BF3, which favours coupling through the α- positions over cross-linking through the β- positions.  The effect of addition of BF3-OEt2 into the electrolytic solution on the electrochemistry of 9 was explored to see if a conductive polymer could be formed in this way (Figure 5.7).   153   Figure 5.7.  CV of 9 with increasing amounts of BF3-OEt2 in 0.1 M [(n-Bu)4N]PF6 in MeCN.  In Figure 5.7, the initial scan without any BF3-OEt2 present shows a large oxidation peak at 1.35 V, which has been assigned to the oxidation at the alkene bridge of 9.230  With the addition of 0.05 ml of BF3-OEt2 to the 10 ml electrolytic solution, the oxidation of the alkene bridge is shifted cathodically by 0.25 V and a decrease in current is observed.  Further addition of BF3-OEt2 results in a further cathodic shift of the peak.  A second oxidation peak also emerges at 1.85 V, which is assigned to the oxidation of the thiophene ring.  Despite diminishing the oxidation at the alkene bridge and lowering the oxidation potential of the thiophene ring, the polymer formed on the electrode was still of low conductivity.   154  5.3.6 Electrochemistry of PEDOT-9 Co-polymer. EDOT was co-polymerized with 9 in order to create a conducting polymer film incorporating the azidostyryl crosslinking functionality.  A similar strategy was employed by Officer et al. when copolymerizing functionalized styrylthiophene groups with bithiophene.235, 236  It was found that with too high of a feed ratio of 9:EDOT, the conductivity of the film degraded.  Thin films were deposited in order to allow for maximum penetration of light through the polymer.  After irradiation, the onset of current increase from polymer oxidation is shifted to a lower potential, suggesting improved ionic conductivity in the undoped state (Figure 5.8).    At the slow scan rate (Figure 5.8 a, b), the maximum current is lower after irradiation than before.  This result suggests that the crosslinking disrupts conjugation across the PEDOT backbone and affects the overall capacity of the film.  However, at the faster scan rates (Figure 5.8 c,d ), the lowered capacity is offset by the improved ionic conductivity of the polymer.  155   Figure 5.8. CV of PEDOT-9 copolymer at a), b) 25 mV s-1 and c,d) 100 mV s-1.  5.3.7 Supercapacitor Devices of PEDOT-9. Type I supercapacitors assembled using the PEDOT-9 films deposited onto ITO were built and tested for their charge storage properties (Figure 5.9).  At 5 mVs-1 (Figure 5.9a), a decrease in capacitance is observed in the device after crosslinking.  This was hypothesized to be an expected consequence of crosslinking as the conjugation of the polymer can be disrupted by a reactive nitrene moiety reacting with the polymer backbone.  A similar decrease in a) b) c) d) 156  capacitance is observed in the irradiated PEDOT-9 electrodes at the potentials more anodic than 0 V.  At higher scan rates (Figure 5.9 b,c), irradiation of the films leads to an improvement in the switching speed of the device.    As in Section 3.3.5, the slope of the plot of the natural logarithm of the discharge current (from 1.0 V to 0.95 V) against the discharge time can be used in conjunction with Equation 3.1 to calculate the RC time constant (Figure 5.9d).  RC time constants of 0.77 and 0.61 s were calculated for the device before and after irradiation, an improvement of 21%.   157   Figure 5.9.  CVs of Type I supercapacitor devices built with PEDOT-9 devices at a) 5       mV s-1, b) 50 mV s-1, c) 100 mV s-1.  The plot of current response as a function of time for the 100 mV s-1 sweep rate is shown in d).  5.4 Conclusion. The (E)-3-4-azidostyrylthiophene compound, 9, with the reactive azido group, and model compound (E)-3-styrylthiophene, 8, were synthesized.  9 was shown to undergo thermolysis which results in a crosslinked polymeric material with improved thermal stability compared to 8.  Similarly, photoexcitation of 9 leads to the conversion of the azido group to a) b) c) d) 158  the nitrene and further reaction.  Unsuccessful attempts at forming conducting polymers of 9 resulted in the deposition of an insulating material on the electrode, due to the oxidation of the alkene bridge and crosslinking of the polymer.  It was found that by adding a Lewis acid, boron trifluoride diethyl etherate, to the monomer solution, the oxidation of the thiophene could be made competitive with oxidation of the alkene.  PEDOT-9 copolymers were electrochemically deposited to investigate if photolysis of 9 could be used to crosslink the polymer.  The PEDOT-9 electrodes exhibited improved ionic diffusion, particularly upon transitioning from the undoped to the doped film.  Type I supercapacitor devices were fabricated from these electrodes and a 21% improvement in the RC time constant after irradiation was calculated based on the discharge kinetics.    159  Chapter 6 General Conclusions and Outlook. 6.1 General Conclusions. Terthiophene-capped Cu and Au NPs were synthesized and their electrochemical properties were studied.  Electrochemical oxidation of Au NPs capped by a thiol-functionalized terthiophene results in a conductive polymer film.  If the thiol functional group of the capping ligand is replaced with a phosphine, the analogous NPs do not undergo electropolymerization.  The difference in their electropolymerizability was attributed to a lower number of phosphine capping ligands on the Au NPs relative to the thiol-capped Au NPs.   The Au NPs were subsequently co-polymerized with EDOT to form Au NP-PEDOT hybrid films.  Selective etching of the Au NPs resulted in a porous polymer film.  The effect of etching on the electrochemical behaviour of the polymer film was probed using cyclic voltammetry and electrochemical impedance spectroscopy.  The size of the electrolyte anion had an effect on the observed electroactivity of the polymer, as etching appeared to have a larger impact on films immersed in an electrolyte containing tetraphenylborate anions than those containing hexafluorophosphare.  The RC time constant of Type I supercapacitors build from the Au NP-PEDOT films were decreased by 35% after etching, a sign of improved discharge kinetics presumably due to improved ionic diffusion.   Attempts to enhance this effect by embedding larger Au NPs into the PEDOT film were unsuccessful.   The Cu NPs, capped with the same thiol-terthiophene group, were also prepared.  The capping ligands on the Cu NPs were prone to photoinduced polymerizations which decreases the solubility of the Cu NP in organic solvents.  The relatively low oxidation potential of the 160  Cu NPs allows for the formation of polymer films with microcrystalline regimes.  X-ray diffraction of the films showed that the crystalline regions were composed of Cu (0) atoms.  However, XPS results show CuO formation at the polymer surface.  PEDOT-Cu NP films had enhanced electroactivity relative to the pure PEDOT films, suggesting that doping the polymer with a highly conductive metal NP could have further positive results. A novel thiophene monomer with an azide functional group was synthesized, which  underwent thermo- and photo- lysis to form both oligomers and polymers.  While electropolymerization of the monomer did not yield a conductive polymer, it can be introduced into PEDOT films by copolymerization in the presence of EDOT.  After exposure to light when doped, the PEDOT-azidothiophene copolymers displayed enhanced electrochemical properties, including faster switching speeds, as evidenced by a 21% decrease in the RC time constant.  This is consistent with increased electrochemical porosity from crosslinking the PEDOT in its doped state due to the the photolysis of the azide.  6.2 Suggestions for future work. Discovering new n-dopeable polymers is critical to the success of polymer supercapacitors as it allows for new high performance Type III supercapacitors to be explored.  The addition of aryl- and fluoro groups to thiophene backbone has been explored and shown promising results.100, 101, 237, 238  Another approach is to create low-bandgap polymers by planarization of the aromatic rings.93, 94, 111   Biaryl azides that undergo photolysis or thermolysis to the singlet nitrene will cyclize to form the fused ring aromatic species.  The first 161  reported example of this was the formation of carbazole via the thermolysis of o-azidobiphenyl (Scheme 6.1).239   Scheme 6.1.  Formation of carbazole via thermolysis or photolysis o-azidobiphenyl.   A synthetic route to azidothiophenes has been established, which involves the lithiation of the bromo-precursor followed by addition of tosylazide to yield the triazene salt.  Fragmentation upon the addition of sodium pyrophosphate yields the azide (Scheme 6.2).240, 241   Scheme 6.2.  Synthesis of 3-azidothiophene.   The photolysis of the azide has been used previously to yield a host of fused ring systems from azido-bithienyl and azidophenylthiophene precursors.242-244  Electropolymerization of these compounds resulted in films which exhibit a high degree of electroactivity.245  Extending 162  this concept from the biaryl to triaryl opens up the possibility to a host of symmetrical and asymetrical oligomers (Figure 6.1) and the fused ring products.       Figure 6.1.  Potential new azidooligomers with phenyl and thienyl groups.  The pyrrole moiety that is formed after ring fusion provides an additional handle to tune the properties of the oligomer.  Replacing N-H bond with N-Me or N-alkyl group will affect the crystal structure packing and the electronics of the oligomer.  Further tuning of the properties can also be achieved by the titration of a Lewis acid which forms a complex with the oligomer and again affect its electronics1, 31, 246.  The principles behind modulating these properties should also carry forward to the polymer.   The PT-Cu NP hybrid system is interesting for its potential to be used as a heterogeneous catalyst system.  Copper has been used as a catalyst for a variety of applications, from CO2 electroreduction247-249 to organic synthesis23, 76, 250.  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PXRD for 7.  180   Figure A.4. Difference FT-IR spectrum for the irradiation of 9.  The spectrum before irradiation was subtracted from the spectrum after irradiation.  A negative ΔT indicates a loss in intensity for a particular IR stretch after irradiation.       

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