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Phosphaalkene monomers and their polymerization Chen, Leixing 2018

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 PHOSPHAALKENE MONOMERS AND THEIR POLYMERIZATION   by  Leixing Chen  B.Sc., St. Francis Xavier University & Changzhou University, 2014  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemistry)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)   April 2018  © Leixing Chen, 2018 ii  Abstract  Living polymerization is a useful technique that is used to synthesize macromolecules with controlled architectures and tailor-made properties. Although this technique is widely used for the polymerization of organic monomers, the living polymerization of inorganic monomers is exceedingly rare. The prospect of synthesizing new inorganic-organic hybrid macromolecules with tailor-made structures is quite attractive due to the chemical functionality imparted by the inorganic moiety. Our group has developed the living anionic polymerization of Mes-P=CPh2 to give chemically functional homo- and block-copolymers with phosphine moieties in the polymer backbone. Thus far, copolymers with styrene and isoprene have been prepared. In Chapter 2, the first poly(methylenephophine)-block-poly(methylmethacrylate) (PMP-b-PMMA) block copolymers will be reported. PMP-b-PMMA's with a variety of chain lengths have been synthesized and fully characterized by NMR spectroscopy, gel permeation chromatography (GPC) and matrix-assisted laser desorption-mass spectrometry (MALDI-MS). To fully understand the process of polymerization, the activation energy (Ea) was determined for the secBuLi-initiated polymerization of Mes-P=CPh2 in nonpolar solvent toluene with TMEDA coordinator (Ea = 16.7 ± 0.7 kcal·mol-1).  In Chapter 3, a simple route to “masked” phosphaalkenes bearing P-Ar (Ar = aryl) and C-H substituents will be explored. The design of monomers bearing substituents smaller than Mesityl at phosphorus and phenyl at carbon, e.g. Mes-P=CPh2, poses considerable synthetic challenge. The present results will provide evidence that a masked phosphaalkene compound has been prepared as a transient species using a masked approach.  iii  The research included in this thesis extends the variety of phosphaalkene-based block copolymers that can be prepared. It also offers new perspectives in synthesis masked phosphaalkene compounds. iv  Lay Summary  Acrylate glass has hundreds of different applications for commercial and home construction due to its competitive properties such as lightweight, durable and shatter resistant. The purpose of this thesis is to synthesize phosphorus-based acrylate glass. The method is by combining phosphorus containing macromolecules with polyacrylate materials, which brings with their new properties, such as potential flame retardant and fluorescent. The synthetic route and characterization of this material are discussed in detailed in this thesis.  v  Preface  This thesis is achieved with helps from others. In Chapter 2, the synthetic route of block copolymer PMP-b-PMMA is invented by sabbatical visitor, Prof. Dr. Kaoru Adachi, of Kyoto Institute of Technology. All the synthetic work was conducted by myself. All DSC measurements for these block copolymers were performed with Ben Herring of the UBC Chemistry Shared Instrument Facility. All GPC measurements were run by Dr. Benjamin W. Rawe. MALDI-MS measurements were done by Marshall Lapawa in the UBC Chemistry Mass Spectrometry Facility.  In Chapter 3, the synthetic route for Mes- P(Cl)-CH2(Cl/Br) (3.8a/b) was initiated by Patrick Werz exchange student, and Shuai Wang (former MSc student). All the synthetic work outlined in this thesis was done by myself. The crystallographic data of 3.13 was collected by Zeyu Han (PhD student).  Chapter 2 and Chapter 3 will be published shortly.   vi  Table of Contents  Abstract .......................................................................................................................................... ii Lay Summary ............................................................................................................................... iv Preface .............................................................................................................................................v Table of Contents ......................................................................................................................... vi List of Tables ................................................................................................................................ ix List of Figures .................................................................................................................................x List of Schemes ........................................................................................................................... xiii List of Abbreviations ...................................................................................................................xv Acknowledgements .................................................................................................................... xix Chapter 1: Introduction ................................................................................................................1 1.1 Polymers ......................................................................................................................... 1 1.2 Living polymerization ..................................................................................................... 5 1.3 Block copolymers ........................................................................................................... 8 1.3.1 Acrylate-based block copolymers ............................................................................... 9 1.3.2 Compounds containing inorganic multiple bonds .................................................... 13 1.3.3 Block copolymers with functional inorganic blocks ................................................ 17 1.4 Outline of thesis ............................................................................................................ 19 1.5 Contributions by other researchers to this work ........................................................... 21 Chapter 2: Synthesis of block copolymer PMP-b-PMMA by anionic polymerization ..........22 2.1 Introduction ................................................................................................................... 22 2.2 Results and Discussion ................................................................................................. 23 vii  2.2.1 Homopolymerization of the monomer (1.1a) to poly(methylenephosphaalkenes) (PMPs) (2.1a-2.7a) in nonpolar solvent in the presence of a chelating ligand (TMEDA). .. 23 2.2.2 Kinetic study of the living nature of phosphaalkene polymerization in toluene/TMEDA system ....................................................................................................... 27 2.2.3 Block copolymerization of the PMPn (2.1a-2.7a) with MMA to poly(methylenephosphine)-block-poly(methyl methacrylate)s (PMPn-b-PMMAm) (2.1b-2.7b) in THF/toluene mixture. .............................................................................................. 31 2.2.4 Other type of poly(methylenephosphine)-block-polyacrylate type polymers .......... 41 2.3 Summary ....................................................................................................................... 44 2.4 Experimental section ..................................................................................................... 44 2.4.1 Materials and general procedures for kinetic study. ................................................. 44 2.4.2 Materials and general procedures for synthesis and characterization of homo PMP and block copolymer PMPn-b-PMMAm. ............................................................................... 46 Chapter 3: Attempt to synthesize “masked” phosphaalkenes .................................................55 3.1 Introduction ................................................................................................................... 55 3.2 Results and discussion .................................................................................................. 59 3.2.1 Synthesis of dichloro(chloromethyl)phosphine (3.7) ............................................... 59 3.2.2 Synthesis of (chloromethyl)mesitylphosphinyl chloride (3.8a) ................................ 60 3.2.3 Synthesis of benzyl(mesityl)(phenyl)phosphane (3.10) ........................................... 63 3.2.4 Preliminary results in the synthesis of “masked” phosphaalkenes ........................... 65 3.3 Summary ....................................................................................................................... 71 3.4 Experimental section ..................................................................................................... 71 Chapter 4: Overall Conclusions and Future Work ..................................................................76 viii  4.1 Summary of thesis work ............................................................................................... 76 4.2 Future work ................................................................................................................... 78 4.3 Closing remarks ............................................................................................................ 80 References .....................................................................................................................................82 Appendices ..................................................................................................................................101 Appendix A The determination of the dn/dc of PMP20-b-PMMA20 (2.4a) ............................ 101 Appendix B Monomer conversion data collected for the polymerization of 1.1a in Toluene/TMEDA system ........................................................................................................ 102  ix  List of Tables  Table 1.1 π Bond energy associated with double bond including the multiple bond of heavier main group elements ..................................................................................................................... 14 Table 2.1 Anionic polymerization of PMP using BnLi in Toluene/TMEDA............................... 26 Table 2.2 Selected data for BnLi-initiated polymerizations of 1.1a conducted in toluene solution in the presence of TMEDA (TMEDA:BnLi = 1:1). ..................................................................... 30 Table 2.3 Anionic block copolymerization of PMP with PMMA using BnLi in toluene/THF solution with LiCl. ........................................................................................................................ 33 Table 2.4 Tacticity of block copolymer 2.1b-2.7b from Figure 2.8. ............................................ 38  x  List of Figures  Figure 1.1 Chemical structure of natural rubber, cellulose nitrate and synthetic polymer bakelite.......................................................................................................................................................... 3 Figure 1.2 General scheme of chain-growth polymerization. ......................................................... 6 Figure 1.3 Different shape of polymers that are synthesized by living polymerization. ................ 7 Figure 1.4 The structures of MMA monomer and PMMA polymer. ........................................... 11 Figure 1.5 Different tacticity of PMMA polymer. ........................................................................ 12 Figure 1.6 Chemical structure of poly(ferrocenylsilane-block-methyl methacrylate) PFS-b-PMMA. ......................................................................................................................................... 13 Figure 1.7 Achievements in the chemistry of multiply-bonded compounds of heavier main group elements. ....................................................................................................................................... 14 Figure 1.8 Stable compounds with heavier main group element containing multiple bonds. ...... 15 Figure 1.9 Examples of isolable compounds featuring phosphorus and carbon multiple bonds. . 15 Figure 1.10 Dimers are isolated for synthesizing Ph-P=CPh2 and o-Tol-P=CPh2. ...................... 16 Figure 1.11 Transition-metal stabilized phosphaalkene compounds. ........................................... 17 Figure 2.1 1H- 13C HSQC spectrum (400 MHz for 1H, CDCl3, 298K) of PMP25 (2.5a).. ............ 26 Figure 2.2 Selected 31P NMR spectra (toluene with TMEDA presence,296.3K) of the benzyl lithium initiated polymerization showing the conversion of 1.1a to PMP over time ([monomer]:[initiator] = 25:1). ..................................................................................................... 27 Figure 2.3 Plot of In[M]0/[M] vs time (h) up to ~97% conversion for the polymerization of 1.1a with 4% BnLi at ca. 5 K temperature intervals between 325 K and 348 K. ................................. 29 xi  Figure 2.4 Graph showing ln[M]0/[M] vs time (h) up to ~50% conversion for the polymerization of 1.1a with 4% BnLi at ~ 5 K temperature intervals between 323 K and 348 K. ....................... 29 Figure 2.5 Arrhenius plot for the BnLi-initiated polymerization of 1.1a. .................................... 31 Figure 2.6 GPC chromatograms (refractive index traces) collected for homopolymer PMPn (2.1a-2.7a) (dotted trace) and block copolymer PMPn-b-PMMAm (2.1b-2.7b) (solid trace). ............... 35 Figure 2.7 MALDI-MS plot of PMP15-b-PMMA50 (2.2b) (n = repeating unit for PMP block, m = repeating unit for PMMA block). ................................................................................................. 36 Figure 2.8: 1H NMR of monomer PA, homopolymer PMP and block copolymers PMPn-b-PMMAm (structure shown in Scheme 2.3). ................................................................................... 38 Figure 2.9 1H-13C HSQC, 1H-13C HMBC, 1H-31P HMBC NMR spectrum (400 MHz for 1H, CDCl3, 298 K) of PMP10-b-PMMA10 (2.1b). ............................................................................... 39 Figure 2.10 The crystallinity plot of homo PMMA and PMP polymer and block copolymers PMPn-b-PMMAm measured by Bruker D8-advance X-ray diffractometer. ................................. 41 Figure 2.11 GPC chromatograms (refractive index traces) collected for homopolymer PMPn (2.8a) (dotted line) and block copolymer PMPn-b-PMMAm (2.8b) (solid line). .......................... 42 Figure 2.12 GPC chromatograms (refractive index traces) collected for homopolymer PMP (2.9a) (dotted line) and block copolymer PMP-b-PtBA (2.9b) (solid line).................................. 44 Figure 3.1 Stabilized 7λ3-phosphanorbornadiene species. ........................................................... 56 Figure 3.2 31P NMR spectrum (CDCl3, 161.9 MHz, 298 K) a) of product mixture 3.8a/b when 3.7 reacts with MesMgBr; b) after treating 3.8a/b with TBACl. .................................................. 61 Figure 3.3  1H NMR spectrum (400 MHz for 1H, CDCl3, 298K) of 3.8a. .................................... 62 Figure 3.4 1H-13C HSQC spectrum (400 MHz for 1H, CDCl3, 298K) of 3.8a. The ordinate shows the 13C{1H} NMR spectrum and the abscissa shows the 1H NMR spectrum. .............................. 63 xii  Figure 3.5 31P NMR spectrum (161.9 MHz, CDCl3, 298 K) of an aliquot removed from the reaction mixture after PhMgBr (2 equiv) was added into 3.8a and stirred for a) 30 mins, b) 15 hours. ............................................................................................................................................. 65 Figure 3.6 31P NMR spectrum (161.9 MHz, CDCl3, 298 K) of a) crude reaction mixture of products of MgA۰3THF with 3.8a/b, b) fraction 2 after purification by column chromatography, c) fraction 3 after purification by column chromatography. ......................................................... 67 Figure 3.7 Molecular structure of 3.13 by ORTEP 3. ................................................................... 68 Figure 3.8 GPC chromatogram (refractive index traces) collected for third fraction. .................. 69 Figure 3.9 31P NMR spectrum (CDCl3, 161.9 MHz, 298 K) from an aliquot of the reaction mixture of a) MgA۰3THF with 3.8a, b) MgA۰3THF with 3.8a and 1,3-cyclohexadiene after 9 h........................................................................................................................................................ 70 Figure 3.10 Structures of 2-methyl-2-phosphabicyclo[2.2.2]oct-5-ene (3.15)  and 2-phenyl-2-phosphabicyclo[2.2.2]oct-5-ene (3.16).111 .................................................................................... 70 Figure 4.1 Proposed structures of poly(methylenephosphines)-block-poly(dimethylsiloxane) PMP-b-PDMS and poly(methylenephosphines)-block-poly(dimethylsilene) PMP-b-PSi. .......... 79 Figure 4.2 2-Phenyl-2-phosphabicyclo[2.2.2]octa-5,7-diene (3.4) and 2-methyl-2-phosphabicyclo[2.2.2]octa-5,7-diene-5,6-dicarboxylic acid (4.1) are reported by Quin’s group. 80  xiii  List of Schemes Scheme 1.1 Reaction scheme of living polymerization of diblock copolymer using living polymerization by sequential addition of monomers. ..................................................................... 8 Scheme 1.2 Possible side reactions during polymerization: (a) Initiator eliminates an alkoxy group from MMA; and (b) backbiting reaction of propagating enolate anion. (Mt=Metal) ........ 10 Scheme 1.3 Bulky diphenylmethyllithium initiators for the living anionic polymerization in the synthesis of polyacrylates. [P = Polymer or other functionality (e.g. nBu)]. ............................... 10 Scheme 1.4 Anionic polymerization of RP=CR’Ph. .................................................................... 18 Scheme 1.5 Synthesis of block copolymers a) PS-b-PMP and b) PI-b-PMP by living anionic polymerization. ............................................................................................................................. 19 Scheme 2.1 Fuoss-Winstein spectrum of anion pairs. .................................................................. 24 Scheme 2.2 Anionic polymerization of 1.1a in toluene with TMEDA presence. ........................ 25 Scheme 2.3 Synthetic route to block copolymerization via a living anionic polymerization to PMP-b-PMMA (2.1b-2.7b). ......................................................................................................... 33 Scheme 2.4 Synthetic route to PMPn homopolymers (2.8a) and their subsequent block copolymerization via a living anionic polymerization to PMPn-b-PMMAm (2.8b). ..................... 42 Scheme 2.5 Synthetic route in block copolymerization of PMP-b-PtBuA (2.9b) by anionic polymerization. ............................................................................................................................. 43 Scheme 3.1 Thermal decomposition of 7λ3-phosphanorbornadiene. ........................................... 55 Scheme 3.2 General procedure to synthesize unprotected 7λ3‑phosphanorbornadiene derivatives (R = tBu, dbabh, HMDS, iPr2N). .................................................................................................. 57 Scheme 3.3 Synthesis of a) dibenzo-7,8-tetramethyldisilabicyclo[2.2.2]octadiene (3.2) and b) dibenzo-7,8-tetramethyldigermabicyclo[2.2.2]octadiene (3.3).97-98 ............................................. 57 xiv  Scheme 3.4 Anionic polymerization of 3.2. ................................................................................. 58 Scheme 3.5 Synthesis of 2-phenyl-2-phosphabicyclo[2,2,2]octa-5,7-diene developed by Quin’s group. ............................................................................................................................................ 58 Scheme 3.6 Postulated synthetic route to “masked” phosphaalkene and its potential application in anionic polymerization. ............................................................................................................ 59 Scheme 3.7 Synthetic route to 3.7. ............................................................................................... 60 Scheme 3.8 Synthetic route to 3.8a. ............................................................................................. 61 Scheme 3.9 Synthesis of benzyl(mesityl)(phenyl)phosphane 3.10. ............................................. 64 Scheme 3.10 a) Proposed reaction of synthesis compound 3.11, b) rationalization of the reaction process leading to the formation of 3.13. ...................................................................................... 66 Scheme 3.11 Reaction of MgA۰3THF and 3.8a with 1,3-cyclohexadiene as trapping agent added after 9 hours. ................................................................................................................................. 70  xv  List of Abbreviations  A                                                                       Anthracene Å                                                                       Angstrom (1×10-10 meters) APT                                                                  Attached Proton Test Bn                                                                     Benzyl br                                                                      Broad Bu                                                                     Butyl c                                                                        Concentration Cis                                                                    Stereochemical descriptor °C                                                                     Degree Celsius ca                                                                             Approximately cal                                                                    Calorie                                                                          Calculated d                                                                       Doublet (NMR spectroscopy)                                                                          Day(s) D                                                                      Deuterium dbabh                                                               2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene dn/dc                                                                Refractive index increment EA                                                                    Elemental analysis                                                                          Ethyl acetate EI                                                                     Electron ionization e.g.                                                                   For example xvi  g                                                                     Gram GPC                                                               Gel permeation chromatography HMDS                                                           Hexamethyldisilazane H3PO4                                                            Phosphoric acid HSQC                                                            Heteronuclear single quantum coherence iPr                                                                  Isopropyl I                                                                     Initiator In                                                                   Integral J                                                                     Coupling constant (NMR spectroscopy) K                                                                    Kelvin KOH                                                              Potassium hydroxide kp                                                                   Propagation rate constant L                                                                    Litre LiCl                                                               Lithium chloride M                                                                   Monomer                                                                       Moles Mn                                                                 Number-average molecular weight Mw                                                                Weight-average molecular weight Me                                                                Methyl Mes                                                               Mesityl MHz                                                             Mega Hertz m                                                                  Meter (unit)                                                                      Multiplet (NMR) xvii  min                                                              Minutes m/z                                                              Mass to charge ratio mol                                                              Mole(s) n                                                                  Amount of substance o                                                                  Ortho ORTEP                                                       Oakridge thermal ellipsoid plot p                                                                  Para P=C                                                             Phosphorus carbon double bond Đ                                                                 Polydispersity index (Mw/Mn) Ph                                                                Phenyl PMP                                                            Poly(methylenephosphine) ppm                                                             Parts per million Rf                                                                 Retention factor s                                                                   Second(s)                                                                      Singlet Sec                                                               Secondary SEC                                                              Size Exclusion Chromatography tBu                                                               tert-Butyl T                                                                  Temperature Tert                                                              Tertiary THF                                                             Tetrahydrofuran Tbt                                                               2,4,6-tris[bis(trimethylsilyl)methyl]phenyl UV                                                               Ultraviolet xviii  vol                                                                Volume δ                                                                   Chemical shift   λ                                                                   Wavelength %                                                                  Percentage °                                                                    Degree xix  Acknowledgements  I offer my enduring gratitude to the faculty, staff and fellow students at UBC Chemistry department, who have inspired me to move ahead in this field. Particular appreciation for my supervisor Prof. Derek P. Gates to bring me into this interesting research area and for his kindness in offering me all the guidance and helps during my years of graduate study.  Working in the Gates’ group is quite pleasant. Thanks all the former and current group members, Dr. Kaoru Adachi, Dr. Kerim Samedov, Dr. Saeid Sadeh, Dr Spencer Serin, Dr Andrew Priegert, Dr Benjamin Rawe, Khatera Hazin, Shuai Wang, Zeyu Han, Chuantian Zhan, Michael Scott, Jeffery Suen, Harvey MacKenzie, Anna Bennett, Henry Walsgrove with their company and their support in this journey. Special thanks to Dr. Kaoru Adachi for providing me with lots of suggestions to these projects. Thanks to Dr Spencer Serin for being my mentor in the lab at the beginning and offering me many creative thoughts with my research. Thanks to Dr. Kerim Samedov for proofreading my thesis and helping me in the lab.  I would like to thank all the NMR, MS, mechanical shop, electronic shop, Chem store and SIF facilities for their support. And financial supports from NSERC and UBC are quite appreciated. Special thanks are owed to my parents, whose have selfless supported me throughout my years of education, both morally and financially. Without them I couldn’t move this far.   1  Chapter 1: Introduction  1.1 Polymers The history of use of polymers traces back to prehistoric times. Polymer-containing materials, such as animal skin, stone, bones, and feathers are ubiquitous in nature and have been extensively used as life necessities.1   The first commercially produced polymer was derived from natural rubber. It consists of approximately 94% cis-polyisoprene, some resins and proteins with small quantities of ash, dirt and water (Figure 1.1). Natural rubber was collected directly from the rubber tree and its name was coined by its unique ability to erase pencil marks by rubbing it on paper.2 Despite this interesting property, natural rubber is soft and sticky which limits its application. In 1839, Goodyear discovered vulcanized rubber by accidently heating natural rubber with elemental sulfur, which significantly changed its stiffness.3 Hard vulcanized rubber has a wide range of industrial applications such as hockey pucks, shoes, tires, gloves, waterproof rubber clothing, toys and parts of some musical instruments.4 Nowadays twenty-five million tonnes of rubber products are traded globally every year.5 Another natural polymer that has had a big influence on our everyday lives is cellulose. The French chemist, Anselme Payen, isolated cellulose in 1839 by treating wood with nitric acid.5 Soon, the derivative of cellulose, cellulose nitrate, was made by Schonbein by exposing cotton to a nitrating agent (Figure 1.1). Partially nitrated cellulose has been used as plastic film, ink ingredient and wood coatings. Highly nitrated cellulose, known as gun cotton, was developed as a propellant and low-order explosive.6 In 1870, the first human-made plastic called celluloid was invented by John Wesley Hyatt by adding camphor as a plasticizer into cellulose nitrate.7 Celluloid 2  was used in the manufacture of lacquers, films and adhesives. In 1893, Count Hilaire de Chardonnet discovered cellulose xanthete. It formed a viscous solution from which cellulose can be regenerated as a continuous fiber (rayon) or film (cellophane).8 Subsequently, the industrial processes were developed for the production of rayon for textiles and cellophane for packaging. In spite of these advances, the limited number of materials based on natural polymers available at that time were not capable of keeping pace with the rapidly growing needs that came with technological and economic progress. The demand for new, easily available, low-cost materials with more advantageous properties grew steadily. It was against that backdrop that in 1907 Leo Baekeland commercialized the first synthetic polymer, Bakelite (Figure 1.1).9 He synthesized these thermoplastic phenolic polymers by condensing phenol with formaldehyde. It is one of the first synthetic plastics that were widely used in electrical insulators, radio and telephone casings due to its excellent electrical nonconductivity and heat-resistant properties. 3   Figure 1.1 Chemical structure of natural rubber, cellulose nitrate and synthetic polymer bakelite.  The industry of synthetic polymers exploded in World War II, as the result of limited supplies of natural polymers such as rubber and cellulose. Synthetic materials, synthetic rubber and nylon, were in high demand as substitutes.10 Nowadays synthetic polymers play a significant role in improving our quality of life. In fact, synthetic polymers have had a huge impact on the areas of health care,11 biotechnology,12 agriculture,13 electronics14 and aerospace.15,16 The development of synthetic polymers catapulted humanity into the Polymer Age after thousands of years of the Bronze Age and Iron Age. Despite the quick development of polymer synthesis, the molecular nature of polymer materials remained unknown until 1920 when it was described by Staudinger.17 He postulated that the polymers were composed of long chains of covalently linked units to give high molecular 4  weight macromolecules. His brilliant work was eventually acknowledged by the scientific community after three decades, when he received the Nobel Prize in Chemistry in recognition of his pioneering research on synthesis and characterization of polymers in 1953. To access synthetic polymer materials, there are two types of methods used that are categorized based on their underlying mechanisms: a) chain growth polymerization (e.g. addition, ring opening, living anionic polymerization etc) and b) step growth polymerization (e.g. most condensation polymerizations).18 Chain growth polymerization is characterized by the addition of the unsaturated monomers to the active polymer chain end, while step growth polymerization typically involves monomers with bifunctional or multiple functional groups and requires reactions with high conversion rates. Polymers are typically characterized with regard to their molecular weight, microstructure, thermal and mechanical properties. The determination of molecular weights, such as number average molecular weight (Mn) and weight average molecular weight (Mw), is very important, because it is a controlling factor in determining solubility, elasticity, processibility and mechanical properties of polymers. Depending on the polymerization methods, synthetic macromolecules may contain individual polymers with different sizes. Dispersity (Đ), formerly known as polydispersity (PDI), is a factor that describes the breadth of a molecular weight distribution within a polymer sample. Dispersity is defined as the Mw divided by Mn. There are a number of methods that are used for determination of the molecular weight of polymers. These include end group analysis, measurement of colligative properties and the most popular gel permeation chromatography (GPC). GPC, also known as size exclusion chromatography (SEC), is the technique to determine molecular weight of polymers based on their hydrodynamic volume. It is often combined with a multiangle light scattering (MALS) detector, a differential refractometer (RI), ultraviolet-visible 5  (UV-Vis) spectrometer and a viscometer. These permit additional properties to be measured and the molecular weights obtained are absolute. For comparison, the traditional approach determines a polymer’s molecular weight relative to polystyrene or another standard in THF. The additional detectors significantly improve the accuracy of molecular weight determination.19 The microstructure of polymers is usually determined by spectroscopic methods, such as nuclear magnetic resonance (NMR), UV/Vis, Fourier-transform infrared (FTIR) and Raman spectroscopy.20 They help to identify the functional groups and composition of polymers. Their thermal properties are characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC measures the glass transition temperature (Tg), melting point (Tm) and crystallization point (Tc) of polymers. Tg is the temperature range where a thermosetting polymer changes from a hard, rigid state to a soft, viscoelastic state. TGA is used for determination the thermal stability of polymers.21 Mechanical properties refer primarily to the strength of polymer films such as tensile strength. The Young’s modulus of elasticity can be characterized by dynamic mechanical analysis (DMA). It is also useful to study the viscoelastic behavior of polymers.22 Wide angle X-ray, small angle X-ray and small angle neutron scattering are used to elucidate the molecular structure of certain crystalline polymers.23  1.2 Living polymerization The traditional standard polymerization routes involve free radical initiation of monomers or condensation polymerization of bifunctional molecules. However, the drawback of these techniques is that they afford polymers with a wide range of chain lengths which may lead to unsatisfactory physical properties.24 6  New polymerization techniques to control molecular weights and dispersity were required to improve properties of synthetic polymers. In 1936, Ziegler proposed using an alkyl lithium initiator to co-polymerize styrene and butadiene.25 He was surprised to notice that there was no termination of the polymerization. Upon addition of monomers, polymerization resumed. Later Szwarc christened this type of reaction “living polymerization” in a sense that a polymer chain never dies without a quenching agent.26 Living polymerization is one type of the chain-growth polymerization. The process of polymerization consists of three steps: initiation, propagation and termination (Figure 1.2). There are different types of living polymerization, such as anionic, cationic, radical and transition metal-mediated polymerization.27   Figure 1.2 General scheme of chain-growth polymerization.  Living polymerization is a powerful tool to control polymers’ physical properties, due to the uniformity of the chain length of the polymer molecules and narrow molecular weight distribution (Đ). It is due to the fact that during polymerization the rate of initiation is much faster than the rate of propagation. Moreover, polymers with architectures, such as block, graft, comb, star, ladder, cyclic shape (Figure 1.3), can be formed using living polymerization.24,28   7   Figure 1.3 Different shape of polymers that are synthesized by living polymerization.  The rapid development of living anionic polymerization started in 1990.29 Provided that the monomers, solvent and initiator are available in sufficient purity styrene, butadiene, ethylene oxide, 2-vinylpyridine (2VP), and alkyl methacrylate are the major monomer classes that are commonly polymerized in a living anionic fashion. These systems display superior properties. The advantages of living anionic polymerization are precisely controlled molecular weights from 103 to 106 g/mol, narrow polydispersity (Đ) usually below 1.05 and highly reactive but stable end group (under appropriate conditions).2 Such characteristics are ideally suited to the synthesis of various linear and branched macromolecules. Recently, living anionic polymerization was recognized as a useful method for synthesizing macromolecules with more complex structures, such as rigid rod-like30 or α-helical and β-strand conformations,31 comb-like,32 multiblock,33 graft,34 dendrimer-like star-branched,35 and hyperbranched polymers.27-28, 36 Perhaps the most important is the living anionic polymerization of olefins that has been employed to access tailor-made block copolymers with novel structures and properties.36b, 37 Much 8  research has been conducted into the synthesis of block copolymers by sequential addition of each monomer and functionalization of the end group of polymers.   1.3 Block copolymers When two or more homopolymer segments are covalently bound together the resultant macromolecule is referred to as a block copolymer. To access such well-defined block copolymer architectures, a well-controlled polymerization protocol is needed. The general method for the preparation of AB diblock copolymers is referred to as the sequential addition technique. By utilizing living polymerization there is no chain transfer or chain termination during propagation. The active species remain alive and propagate upon the addition of subsequent monomers. Once the polymerization completes, a “quenching” agent is added to terminate the reaction (Scheme 1.1).38, 39   Scheme 1.1 Reaction scheme of living polymerization of diblock copolymer using living polymerization by sequential addition of monomers.  There are some unique advantages of block copolymers. One of the attractive properties of block copolymers is their self-assembly to afford nanometer sized macromolecular aggregates with ordered structures that display a wide range of morphologies, including spheres, cylinders, lamellae, vesicles and many other complex assemblies. Self-assembly can be accomplished by utilizing different solubility of each block in selective solvents. Different solubilities cause an 9  insoluble segment to become a core center and a soluble segment to become a corona. Depending on the size of each block, the morphology of micelles varies.40 These aggregates are considered to be useful carriers in application of drug delivery, photovoltaics, catalysis, surfactant.41 The other distinct property of block copolymers is their chain regularity by comparison to random copolymers. It provided the possibility of crystallization with ordered chain packing. There are multiple thermal transitions possible for block copolymers such as glass transition temperature (Tg), crystalline melting points (Tm) and/or liquid crystal transitions (TLC). In contrast, random polymers display glass transitions only. The properties of block copolymers such as tensile strength, modulus and elasticity have also proved to be superior to those of random copolymers. Organic block copolymers have been widely accessible especially through the copolymerization of olefins, for example, styrene-butadiene, styrene-isoprene, polyacrylic and polyvinylpyridine containing block copolymers.  1.3.1 Acrylate-based block copolymers The generation of block copolymers incorporating acrylate blocks is very challenging due to the difficulty in performing living polymerizations of acrylic monomers. The living polymerization of acrylates is complicated by side reactions involving the ester functionality which compete with initiation and propagation reactions involving the olefinic moiety.42 As shown in Scheme 1.2, the carbonyl group in MMA might be attacked by the initiating (or propagating) anion to induce elimination [Scheme 1.2(a)] or backbiting to form a six-membered ring [Scheme 1.2(b)]. Both result in termination of the polymerization (Scheme 1.2). Thus, the choice of solvent and initiating anions is crucial to efficiently polymerize acrylates with minimal side-reactions. Typically, the bulky π-stabilized diphenylmethyllithium is chosen as the initiator (Scheme 1.3).28b, 10  43 In addition, the living anionic polymerization of acrylates [e.g. methyl acrylate (MA), methyl methacrylate (MMA), t-butyl acrylate (tBuA)] requires low temperatures and solvents with low to moderate polarity.    Scheme 1.2 Possible side reactions during polymerization: (a) Initiator eliminates an alkoxy group from MMA; and (b) backbiting reaction of propagating enolate anion. (Mt=Metal)   Scheme 1.3 Bulky diphenylmethyllithium initiators for the living anionic polymerization in the synthesis of polyacrylates. [  = Polymer or other functionality (e.g. nBu)].   Despite these difficulties, acrylate-containing block copolymers have attracted attention because of their self-assembly characteristics and biocompatibility. These characteristics have made them a subject of investigation as drug delivery agents,31a, 31b, 32, 42 self-healing elastomers,44 membranes,45 and stimuli responsive applications.33 Various block copolymers, such as poly(methy1 methacrylate)-block-poly(tert-butyl acrylate) (PMMA-b-PtBA),46 polystyrene-11  block-poly(tert-butyl acrylate) (PS-b-PtBuA),47 poly(2-vinylpyridine)-block-poly(dimethylamino)ethyl methacrylate) (P2VP-b-PDMAEMA), 48 polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA),49 poly(N-isopropylacrylamide-block-butylmethacrylate) (PIPAAm-b-PBMA),50 have been synthesized utilizing living anionic polymerization.  Amongst all polyacrylate-containing block copolymers, those containing poly(methyl methacrylate) (PMMA) blocks have attracted the most attention due to the unique properties of this polymer segment (Figure 1.4). For instance, PMMA is a transparent thermoplastic that is widely used as a substitute for borosilicate glass, due to its light weight, high impact strength, easy processability and shatter-resistance.51 The distinct physical properties of PMMA are demonstrated by a high tolerance to irradiation with UV light and excellent thermal stability. PMMA also displays remarkable mechanical properties such as a high Young’s modulus and low elongation at breakage, thereby making it one of the hardest thermoplastics.52   Figure 1.4 The structures of MMA monomer and PMMA polymer.  PMMA containing macromolecules have various applications including their use as: optical materials,53 pneumatic actuators,54 sensors,55 the stationary phase in columns,56 and conductive devices,57 biomedical materials,58 and drug-delivery systems.59 PMMA-containing 12  copolymers with carbon nanotubes or inorganic materials are also important in the use of nanotechnology because of their compatibility and easy processibility.  As for the stereochemistry of adjacent chiral centers within a polymer, there are three types of tacticity in the PMMA polymers: atactic, isotactic and syndiotactic (Figure 1.5).60 The tacticity of PMMA has a profound effect on its physical properties (e.g glass transition temperature (Tg), solubility, crystallinity and stability towards hydrolysis). For example, syndiotactic PMMA displays a significantly higher Tg (130 °C) than isotactic PMMA (Tg of 55 °C) and atactic PMMA’s Tg of 120 ° C.61 In addition, isotactic PMMA is partially crystalline whereas syndiotactic and atactic PMMA are both amorphous.    Figure 1.5 Different tacticity of PMMA polymer.  The vast majority of studies involving acrylate-containing block copolymers have focused on all-organic systems. Polymers such as polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) and poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) have been studied extensively.62 However, there are few examples of inorganic functional PMMA block copolymers. The incorporation of inorganic segment into polyacrylate block copolymers was first introduced by Ian Manners and co-workers in 2004. Poly(ferrocenylsilane-block-methyl methacrylate) (PFS-b-PMMA) (Figure 1.6) was synthesized by living anionic polymerization, which gave excellent control of molecular weight and molar mass distribution (Đ) as well as the 13  specific architectures such as block and graft copolymers.63 One of the problems with preparing block copolymers of acrylates and inorganic functionalities is a tremendous lack of inorganic monomers that are suitable for living polymerization.   Figure 1.6 Chemical structure of poly(ferrocenylsilane-block-methyl methacrylate) PFS-b-PMMA.  1.3.2 Compounds containing inorganic multiple bonds The limited number of inorganic monomers are available resulting from the misunderstanding of the inorganic multiple bonds for a long time. The formation of inorganic multiple bonds of type (np-np)π (n > 2) was considered to be impossible well into the 1960’s. This fact was reflected in the classic “double bond rule” frequently found in the textbooks of that era which stated that “chemical elements with a principle quantum number greater than 2 for their valence electrons should not form multiple bonds with themselves or other elements”.64 A major breakthrough that shattered the double bond rule occurred when the first isolable compounds with P=C, Si=C, Si=Si, P=P bonds were reported between 1978 and 1981.65 Since then the explosive development in the chemistry of multiply bonded compounds of heavier main group elements took off. Nowadays multiple examples of stable unsaturated compounds with heavier main group elements have been reported as shown in Figure 1.7.65-66,67  14   Figure 1.7 Achievements in the chemistry of multiply-bonded compounds of heavier main group elements.   The challenges associated with the synthesis of such compounds results from their intrinsic instability. The large size of heavier atoms decreases the extent of the p-p-orbitals’ overlap leading to a decrease of the π bond energy. For example, Table 1.1 shows that π bond energy of the Si=Si bond (25 kJ mol-1) is significantly lower than of that the C=C bond (65 kJ mol-1), which renders intrinsic unstable disilene compounds.  Table 1.1 π Bond energy associated with double bond including the multiple bond of heavier main group elements  Multiple bond C=C N=N P=N Si=C P=P Si=Si π bond energy (kcal mol-1) 65 60 44 38 34 25  To kinetically stabilize E=E’ double bonds, bulky substituents are required. They exert their stability effect by lowering the reaction rates of reactions involving E=E’ double bonds. By employing these techniques, some examples (Figure 1.8) of stable compounds containing multiple bonded main group elements were successfully synthesized.65-66  15   Figure 1.8 Stable compounds with heavier main group element containing multiple bonds.  Incorporating p-block elements into unsaturated compounds is a growing area. The isolation of compounds featuring P=C bonds is of interest to our group. Phosphaalkenes as alkene analogues share similar reactivity and properties with alkenes.68 That, in turn, allows for a rich and exciting chemistry including 1,2-addition, Diels-Alder reaction, Cope rearrangement, coordination reaction.68 The discovery of the first stable phosphorus carbon multiple bonds was based on the electronic delocalization, phosphamethine cyanines 1.369 and phosphines 1.470 (Figure 1.9) were successfully synthesized. In 1978, the first kinetically stabled phosphaalkene compound 1.567c (Figure 1.9) was isolated by means of attaching sterically encumbering groups to it. A series of isolable phosphaalkenes 1.1a-e were successfully synthesized by our group extending the family of kinetically stabilized phosphaalkenes.  Figure 1.9 Examples of isolable compounds featuring phosphorus and carbon multiple bonds. 16   The expansion of phosphaalkene monomers types is attractive. Thus, the synthesis of phosphaalkenes bearing substituents “smaller” than the 2,6-xylyl group at the P atom and phenyl group at the C atom was performed. Although it might appear trivial to prepare P=C bonded compounds bearing small substituents such as hydro, alkyl or aryl substituents, phosphaalkenes such as H-P=CH2, Me-P=CH2 and Ph-P=CH2 can only be generated in situ in the gas phase or in dilute solution with fleeting existence.67i, 71 More recently, our group targeted Ph-P=CPh2 and o-Tol-P=CPh2 which were expected to be more kinetically stable. The phospha-Peterson route was employed in an attempt to synthesize these compounds. However, instead of monomeric compounds they are found in equilibrium with their corresponding [1,2]diphosphetane dimers as shown in Figure 1.10. In case of Ph-P=CHPh, an in situ polymerization in the reaction mixture occurs, and no monomeric Ph-P=CHPh can be isolated.72    Figure 1.10 Dimers are isolated for synthesizing Ph-P=CPh2 and o-Tol-P=CPh2.  Stabilizing phosphaalkene double bonds by coordinating them to transition-metals is another possible technique. Mathey et. al first synthesized molybdenum- and tungsten-stabilized phosphaalkene in 1988 as shown in Figure 1.11 by phospha-Wittig reaction.73 But examples of such compounds are still limited because the isomerization between P=C and C=C or addition reactions easily occur. New methods in synthesizing stable phosphaalkenes bearing smaller groups are still underdeveloped. 17    Figure 1.11 Transition-metal stabilized phosphaalkene compounds.  Stable compounds of heavier element-containing E=E’ bonds are also of particular interest in the application in polymer science.74 The introduction of an inorganic segment into an organic polymer brings additional functionalities into the polymers. Unsaturated main group element-containing compounds are potentially suitable monomers for addition polymerization. However, stable compounds with bulky substituents have higher activation barriers that could partially or completely inhibit any reactivity of these compounds. It is an eminent challenge to find the proper balance between the size of substituent stabilizing the E=E’ π bond in such compounds, while keeping up their suitability as potential monomers for polymerization.   1.3.3 Block copolymers with functional inorganic blocks Given the tradeoff in reactivity between stable inorganic unsaturated compounds and suitable monomers for addition polymerization, there are some  compounds such as silenes66a and germenes36a has been found can be polymerized by anionic polymerization in a non-living fashion. Surprisingly, the inorganic and organic hybrid monomers, phosphaalkenes 1.1a-1.1e, can be polymerized in living fashion. We have shown that the monomer, 1.1a-1.1e can be polymerized 18  using radical66c, 75 or anionic74c, 75b,30 methods to afford poly(methylene)phosphines (PMPs) 1.2a-1.2e (Scheme 1.4). Strikingly, activation of the C-H bond of an ortho-bound CH3 group has been observed in the polymerization of 1.1a. Later the proton transfer also was observed in the polymerization of 1.1b.   Scheme 1.4 Anionic polymerization of RP=CR’Ph.  Importantly, we have shown that the anionic polymerization of Mes-P=CPh2, 1.1a, is living.74c Employing living polystyrene or polyisoprene as the initiator affords novel block copolymers PS-b-PMP and PI-b-PMP, respectively (Scheme 1.5).74c 76 It was found that PS-b-PMP can be employed as a polymer support for palladium-catalyzed Suzuki coupling.74c The solution self-assembly of amphiphilic PMP-b-PI block copolymers provided a powerful tool to enable fabrication of nanoparticles with different morphologies, such as spheres, worms, and large aggregates. Moreover PI-b-PMP is an excellent template that has been used for the preparation of gold(I) nanostructures.76  19   Scheme 1.5 Synthesis of block copolymers a) PS-b-PMP and b) PI-b-PMP by living anionic polymerization.  Although it was not possible to employ living PMP (1.2a-1.2e) as an anionic initiator for styrene or isoprene polymerization, we noted its similarity to diphenylmethyl lithium, a typical initiator for the living anionic polymerization of acrylates.47-48, 77 This thesis presents the first block copolymers derived from the living anionic sequential polymerization of phosphaalkenes 1.1a and 1.1b with acrylates, MMA and tBuA.  1.4 Outline of thesis Living anionic polymerization technique has become very popular because of its distinct advantageous features such as producing polymers with tailor-made structures and controllable 20  molecular weight. Certain type of morphology can be made through use of this technique such as e.g. block copolymer. Taking this approach from organic macromolecules to organic-inorganic hybrid macromolecules is creating materials with evermore fascinating properties. To explore the phosphaalkene-based block copolymer, previously our group synthesized polystyrene-block-poly(methylenephosphine) (PS-b-PMP) and polyisoprene-block-poly(methylenephosphine) (PI-b-PMP).74c In chapter 2 it is described how poly(methylenephosphine) (PMP) is used for the first time as a living anionic polymerization initiator to initiate other monomers. The synthetic process and characterization of poly(methylenephosphine)-block-polymethyl methacrylate (PMP-b-PMMA) are discussed therein. Kinetic study of polymerization phosphaalkene in nonpolar toluene system with coordinating ligand TMEDA presence helps to fully understand this system. Various compositions of poly(methylenephosphine)-block-polyacrylates have been obtained by changing each segment, for example, instead of 1.1a as monomer 1.1b is used to form block copolymer PMP’-b-PMMA or varying polyacrylates segment to synthesize poly(methylenephosphine)-block-polytertbutylacryates (PMP-b-PtBA). Extending the family of polyphosphaalkene-based macromolecules has been limited by the limited number of isolable phosphaalkene molecules available. Thus, the discovery of new isolable and stable phosphaalkene monomers bearing a wide range of substituents is desirable. For a long period of time, though, this area didn’t draw much interest because of the inherent instability of phosphaalkenes. However, as shown previously a stable monomer, Mes-P=CPh2, can be synthesized and polymerized by anionic and radical polymerization. Shrinking the size of substituents attached around the P=C bond is of further interest. Chapter 3 introduces a new route to formation of stable phosphaalkene precursors bearing groups with reduced steric bulk. The preliminary results in synthesis of a masked phosphaalkene which is supposed to be a suitable 21  monomer for addition polymerization are described therein as well. Finally, future work is presented in Chapter 4.  1.5 Contributions by other researchers to this work Some of the work in this thesis was done in cooperation with others. In Chapter 2, the synthetic route to PMP-b-PMMA was discovered by sabbatical visitor, Prof. Dr. Kaoru Adachi, of Kyoto Institute of Technology. All the synthetic work was conducted by myself. All DSC measurements for these block copolymers were performed with the assistance of Ben Herring of the UBC Chemistry Shared Instrument Facility. All GPC measurements were recorded by Dr. Benjamin W. Rawe using samples that I prepared. MALDI-TOF MS measurements performed by Marshall Lapawa in the UBC Chemistry Mass Spectrometry Facility. In Chapter 3, the synthetic research for Mes-P(Cl)-CH2(Cl/Br) (3.8a/b) was initiated by Patrick Werz, exchange student, and Shuai Wang (former MSc student). All the synthetic work outlined in this thesis was done by myself. The crystallographic data of 3.13 was collected by Zeyu Han (PhD student).   22  Chapter 2: Synthesis of block copolymer PMP-b-PMMA by anionic polymerization  2.1  Introduction Polymers have a wide range of application in our daily life including packaging, electronics, automotive, aerospace and medical devices.78 Therefore, various polymerization methods have been developed for synthesizing polymers. Of all polymerization methods, living polymerization is the ideal technique to allow exact control of molecular weight and morphology of macromolecules.24 It offers superior precision in terms molecular weight control coupled with the wide range of molecular weights obtainable as well as narrow polydispersity and custom designed polymer structure (e.g. block, graft, star, ladder, cyclic and amphiphilic type of copolymers). Various techniques such as anionic, cationic, radical and transition metal-mediated polymerization have been developed to accomplish the living behavior.24 Block copolymer is of special interest owing to its custom-designed novel properties, which have been prepared via living polymerization by properly choosing constituting building blocks. Recently block copolymers containing polyacrylates units have been developed as a new type of thermoplastic elastomers in industry.44 Although living anionic polymerization has been widely used to polymerize various purely organic monomers such as styrene, dienes and ethylene oxide, there is only a limited number of examples for its application in polymerization of hybrid organic–inorganic monomers, especially the ones involving phosphorus. Phosphorus containing polymers exhibit peculiar complexing properties and were used as corrosion inhibiting agent,79 flame-retardant materials and biomedical materials with superior performance.80  23  The challenge being faced in synthesizing phosphorus-containing polymers is the lack of suitable monomers. Our group was successfully synthesized a couple of stable phosphaalkene compounds, such as Mes-P=CPh2 (1.1a) and Xyl-P=CPh2 (1.1b) which are well-behaved monomers in anionic polymerization. Previously only two block copolymers containing 1.1a monomer unit have been reported, polystyrene-block-poly(methylenephosphine) (PS-b-PMP) and polyisoprene-block-poly(methylenephosphine) (PI-b-PMP).76 In this work we report the first time poly(methylenephosphine)-block-polyacrylates type polymer.   2.2 Results and Discussion 2.2.1 Homopolymerization of the monomer (1.1a) to poly(methylenephosphaalkenes) (PMPs) (2.1a-2.7a) in nonpolar solvent in the presence of a chelating ligand (TMEDA). Since the initiation step in anionic polymerizations is usually much faster than the propagation rate, the polymerization rate in such polymerization is determined by the propagation rate of the polymer chain. In order to better control morphology and molecular weight of polymers, controllable reactivity of the living chain-end anion becomes the key factor. That, in turn, is mainly affected by three factors: solvent polarity, intermolecular ionic interactions and the size of metallic counter ion.81 Anionic polymerizations of 1.1a in polar solvents such as THF and glyme with nBuLi lithium initiators have been extensively studied in our group.82 74d, 76 To assess the influence of the solvent polarity on the polymerization of compound 1.1a, a change of solvent for polymerization of 1.1a in a nonpolar solvent, toluene, in the presence of TMEDA as a chelating ligand was studied. Contrary to our previous studies the initiator used in this study is the much milder benzyllithium (BnLi) (pKa=41), generated in situ by the reaction of secBuLi (pKa=51) with toluene. The reactivity of initiator can be promoted by varying the nature of the lithium cation in 24  the ion pairs that form. Fuoss-Winstein spectrum of anions theory states (see Scheme 2.1) that four types of ion pairs exist with different intermolecular ion distances being the decisive difference among them: aggregated ion pairs, contact ion pairs, solvent separated ion pairs and free ions.4     Scheme 2.1 Fuoss-Winstein spectrum of anion pairs.   In nonpolar solvents such as toluene, BnLi (4 mol%) exists in aggregated ion pairs. To increase the interionic distance, a Lewis base/chelating ligand TMEDA (4 mol%) is added to coordinate lithium cation and form a benzyl anion-lithium cation contact ion pair. Benzyl anion then initiates the polymerization with the monomer 1.1a and propagates at 50 ºC, whereupon intermediate anion is formed (Scheme 2.2). The polymerization was conveniently monitored using 31P{1H} NMR spectroscopy and after 7 h the signal corresponding to phosphaalkene (δ = 234) was completely replaced by a signal at –9 ppm assigned to 2.5a. Treatment of the deep red solution, characteristic of living PMP, with MeOH (2 drops) resulted in a color change to pale yellow indicative of termination of the propagating anion. Polymer 2.5a was isolated as a colorless solid by concentrating the reaction solution and precipitating with methanol (2).  25   Scheme 2.2 Anionic polymerization of 1.1a in toluene with TMEDA presence.  The isolated homopolymer, 2.5a was analyzed by using one- and two-dimensional 1H, 13C and 31P NMR spectroscopy. The 1H and 13C{1H}-HSQC NMR spectrum (Figure 2.1) was particularly informative showing clear cross correlations assigned to CH3 (13C:  = 21.1, 1H:  = 2.0), CHPh2 (13C:  = 52.0, 1H:  = 4.7), CH2 (13C:  = 32.5, 1H:  = 3.4) and the aryl moiety (13C:  = 128.3, 1H:  = 7.1). These data are consistent with microstructure 2.5a (x >> y) which has previously been observed in radical-initiated polymerization of 1.1a.75b Activation of the C-H bond of an ortho-bound CH3 group of the P-Mes moieties occurs during polymerization of 1.1a under these conditions. GPC-MALS analysis of polymer 2.5a revealed a monodisperse distribution with molecular weight (Mn = 7100 g mol-1; PDI = 1.10) which is corresponds to a degree of polymerization of ca. 23 as close to predicted from monomer-to-initiator ratio. Based on the successful synthesis of 2.5a, a series of polymers 2.1a-2.7a can be achieved following the same procedure but varying the amount of 1.1a.    26   Figure 2.1 1H- 13C HSQC spectrum (400 MHz for 1H, CDCl3, 298K) of PMP25 (2.5a). The ordinate shows the 13C{1H} NMR spectrum and the abscissa shows the 1H NMR spectrum.  Table 2.1 Anionic polymerization of PMP using BnLi in Toluene/TMEDA. Entry[a] M1/I [b] Mn(calcd)[c]            [g mol-1] Mn(obsd)[d]             [g mol-1] Đ[d] 2.1a 10:1 3252 3400 1.06 2.2a 15:1 4832 4800 1.13 2.3a 15:1 5148 5100 1.16 2.4a 20:1 6412 5500 1.08 2.5a 25:1 8308 7100 1.10 2.6a 25:1 8308 7100 1.13 2.7a 30:1 9576 9000 1.08 [a] Condition: M1 was polymerized in Toluene with TMEDA present at 50 ºC. Upon complete consumption of M1, half of the reaction mixtures were quenched with MeOH giving 2.1a-2.7a. [b] M1 = 1.1a, I= BnLi. [c] Mn(cald) = (Mn of monomer) × (convn)/100 × [monomer]/[initiator] + (Mn of initiator fragment) + (Mn of terminator fragment). [d] Evaluated by triple detection MALS-GPC. 27  2.2.2 Kinetic study of the living nature of phosphaalkene polymerization in toluene/TMEDA system We have previously reported kinetic studies of the living anionic polymerization of 1.1a (M:I = 50:1) in glyme using nBuLi as the initiator.83 In the present work, we have investigated the polymerization rate for the secBuLi initiated polymerization of 1.1a (M:I = 25:1) in toluene with the coordinating ligand TMEDA (TMEDA:Li = 1:1). The progress of the polymerization was monitored by recording the 31P NMR spectrum at 30 min intervals. For the reaction performed at 50 °C, the 31P NMR spectra are shown in Figure 2.2 and reveal that 97% of the 1.1a (δ31P = 234 ppm) was consumed to form PMP homopolymer (δ31P = –9 ppm) after 7 h.    Figure 2.2 Selected 31P NMR spectra (toluene with TMEDA presence,296.3K) of the benzyl lithium initiated polymerization showing the conversion of 1.1a to PMP over time ([monomer]:[initiator] = 25:1). 1.1a PMP 28  Careful integration of the spectra permitted the determination of the concentration of monomer as a function of time. The reaction follows pseudo first order kinetics up to ca. 50 % conversion as depicted in Figure 2.3 for polymerizations conducted at six different temperatures (50 °C to 75 °C). The propagation rate constants (kp) were determined from Figure 2.4 at each temperature and the results are given in Table 2.2. Above 50 % conversion, the data deviates significantly from linearity as shown in Figure 2.3 displays. Similar observations were made with the living anionic polymerization of 1.1a in glyme.83 According to the previous study in the polymerization of olefins, the apparent rate constant kp is expressed as equation I due to the solvation effect. There is a free ion-ion-pair equilibrium of the living chain end during propagation.84 It is possible that the polymerization of 1.1a in toluene and TMEDA system also exhibits the equilibrium state of the active end between free ion and ion pair during propagation. In this case, temperature shifts the equilibrium, which further alters the propagation rate constant. Future study is required to determine the kpfree-ion and kpion-pair separately.  −d[M]dt= 𝑘pfree−ion[free − ion chain ends][M] + 𝑘pion−pair[𝑖on − pair chain ends][M]   (I) 29   Figure 2.3 Plot of In[M]0/[M] vs time (h) up to ~97% conversion for the polymerization of 1.1a with 4% BnLi at ca. 5 K temperature intervals between 325 K and 348 K.   Figure 2.4 Graph showing ln[M]0/[M] vs time (h) up to ~50% conversion for the polymerization of 1.1a with 4% BnLi at ~ 5 K temperature intervals between 323 K and 348 K. These plots of In[M]0/[M] vs time (h) were fitted to a linear least-squares function to determine rate constant (kp) shown in Table 2.2.    00.511.522.533.544.50 2 4 6In[M] 0/[M]Time (h)325.2K328.2K333.2K338.2K343.2K348.2K00.511.522.533.50 0.5 1 1.5 2 2.5 3 3.5 4 4.5In[M] 0/[M]Time (h)323.2K328.2K333.2K338.2K343.2K348.2K30  Table 2.2 Selected data for BnLi-initiated polymerizations of 1.1a conducted in toluene solution in the presence of TMEDA (TMEDA:BnLi = 1:1). Entry [M]:[I][a] Temp (K) kp[b] (Lmol-1h-1) Mn (calcd)[c] (g mol-1)  Mn (obsd)[d] (g mol-1)  Đ 1 25:1 323.2 40.3 ± 4.7 7992 8000 1.12 2 25:1 328.2 81.33 ± 9.7 7992 7800 1.07 3 25:1 333.2 87.93 ± 10.3 7992 7900 1.05 4 25:1 338.2 105.43 ± 12.3 7992 7900 1.10 5 25:1 343.2 147.93 ± 17.0 7992 7800 1.07 6 25:1 348.2 147.33 ± 16.9 7992 7900 1.09 [a][1.1a]:[BnLi]. [b]Apparent propagation rate constant. [c]Mn(calcd) = (Mn of monomer) × (convn)/100 × [monomer]/[initiator] + (Mn of initiator fragment) + (Mn of terminator fragment). [d]Absolute molecular weights were determined using triple-detection GPC (refractive index increment dn/dc = 0.2387 was determined off-line for 2.1a-2.7a).    Each polymerization was quenched by the addition of MeOH (2 drop) and the resultant polymers were isolated by precipitation of a THF solution with hexanes ( 2). Analysis of the isolated polymer by GPC-MALS was consistent with the expected degree of polymerization of approximately 25 at all temperatures as shown in Table 2.2. The rate constant data was analyzed using the Arrhenius plot (Figure 2.5) and, accordingly, the activation energy (Ea = 16.7 ± 0.7 kcal mol-1) and pre-exponential factor (A = 9.2 × 1012 M-1 h-1) were determined from the slope and intercept, respectively (Equation II). For comparison, the Ea for the nBuLi-initiated polymerization of 1.1a in glyme solution was previously determined to be 14.0 ± 0.9 kcal mol-1, and the preexponential factor (A = 4.4 × 1011 M-1 h-1).83 Although these energies do not differ considerably when the uncertainty in their measurement is considered, a higher activation energy for 31  polymerizations conducted in nonpolar toluene when compared to those performed in polar glyme could easily be rationalized.   In𝑘𝑝 = In𝐴 −𝐸𝑎𝑅(1𝑇)       (II)   Figure 2.5 Arrhenius plot for the BnLi-initiated polymerization of 1.1a. The ln kp (kp = apparent propagation rate constant) vs 1/T (K-1) data were fit to a linear function. The linear least-squares function (y = -8405x + 29.845) had an R2 value of 0.9567. An activation energy (Ea) of 16.7 ± 0.7 kcal mol-1 was estimated for the polymerization of phosphaalkene 1.1a. Error bars are reported with 95% confidence.    2.2.3 Block copolymerization of the PMPn (2.1a-2.7a) with MMA to poly(methylenephosphine)-block-poly(methyl methacrylate)s (PMPn-b-PMMAm) (2.1b-2.7b) in THF/toluene mixture. The prospect to utilize the –CPh2  anion of living 2.1a-2.7a as an initiator for methyl methacrylate was intriguing since we have previously been unable to initiate olefinic monomers using this species. We therefore employed procedures typically used for the living anionic polymerization of acrylates to explore this possibility.77a, 81, 85 For example, a red toluene solution 3.74.24.75.22.85 2.95 3.05Inkp1/T (K-1) × 10332  of living PMP was prepared from 1.1a and BnLi (M:I = 25:1) in the presence of TMEDA as described above. To adjust the polarity for the polymerization, THF was added. It is expected that the interionic distance between diphenyl carbon anion and lithium counter cation would increase upon THF addition from contact ion pairs to the solvent-separated ion pairs or even free ions on Fuoss-Winstein spectrum shown in Scheme 2.1. The increased reactivity of the initiating anion would improve the polymerization rate tremendously, but that could also cause side reactions to occur as shown in Scheme 1.2. The way to prevent this is to use LiCl additive to suppress the participation of free ions during propagation of MMA.43b Prior to adding methyl methacrylate, the solution was treated with LiCl (20 mol%) in THF and cooled to –78 °C to better control of the growth centers. Upon adding methyl methacrylate (4 equiv) in THF, the color of solution immediately changed from deep red to light yellow. The reaction mixture was slowly warmed to room temperature. The polymerization was terminated by the addition of degassed methanol (2 drops), upon which the yellow color of the reaction mixture became much paler, towards colorless. The reaction mixture was concentrated and was added to a vigorously stirred degassed methanol solution, from which the polymer precipitated as a white solid. The material was purified by two further precipitations and dried in vacuo (Scheme 2.3). GPC-MALS analysis revealed a Mn of 18000 g mol-1 and Đ of 1.09, which is quite close to the expected Mn of 17992 g mol-1. A series of block copolymers (Table 2.3), 2.1b-2.7b, by using a similar method only varying the amount of monomers with a range of PMP block lengths (n = 10-30) and PMMA block lengths (m = 10-100) Each copolymer was analyzed by GPC-MALS. The measured molecular weights of 2.1b-2.7b range from 4300-20000 g mol-1 were close to those calculated from the monomer-to-initiator ratio method. The deviation of experimental Mn from calculated Mn are within 0.04%-4% except for PMP20-b-PMMA20 has 15% deviation. The copolymerization 33  reactions were quite successful with narrow dispersities being observed (Đ = 1.05-1.10). Selected GPC traces (RI data) of the homo- and co-polymers are presented in Figure 2.6.    Scheme 2.3 Synthetic route to block copolymerization via a living anionic polymerization to PMP-b-PMMA (2.1b-2.7b).            Table 2.3 Anionic block copolymerization of PMP with PMMA using BnLi in toluene/THF solution with LiCl. 34    2.X a 2.X b Entry[a]  M1/I/M2 [b] Mn(calcd)[c]            [g mol-1] Mn(obsd)[d]             [g mol-1] Đ[d] Mn(calcd)[c]            [g mol-1] Mn(obsd)[d]             [g mol-1] Đ[d] dn/dc[e] X=1 10:1:10 3252 3400 1.06 4252 4300 1.07 0.1897 X=2 15:1:50 4832 4800 1.13 9832 10100 1.08 0.1373 X=3 15:1:60 5148 5100 1.16 10832 10900 1.09 0.1276 X=4 20:1:20 6412 5500 1.08 8412 7100 1.06 0.1897 X=5 25:1:50 8308 7100 1.10 12992 12500 1.09 0.1625 X=6 25:1:100 8308 7100 1.13 17992 18000 1.08 0.1295 X=7 30:1:100 9576 9000 1.08 19572 19800 1.05 0.1373  [a]Condition: M1 was polymerized in toluene with TMEDA present at 50 ºC. Upon complete consumption of M1, half of the reaction mixtures were quenched with MeOH giving 2.Xa. The other half of the reaction mixture was cooling to -78 ºC, added LiCl, then M2. After the polymerization finished, the reaction mixtures were quenched with MeOH giving 2.Xb. [b]M1 = 1.1a, I= BnLi, M2 = MMA. [c]Mn(calcd) = (Mn of monomer) × (convn)/100 × [monomer]/[initiator] + (Mn of initiator fragment) + (Mn of terminator fragment). [d]Evaluated by triple detection MALS-GPC. [e]Cauchy plots (see Figure A.1) to perform extrapolations of dn/dc of PMPn-b-PMMAm by using the set of different concentration PMP-b-PMMA solution. The dn/dc was calculated using eq. 1 (see experimental section).  35   Figure 2.6 GPC chromatograms (refractive index traces) collected for homopolymer PMPn (2.1a-2.7a) (dotted trace) and block copolymer PMPn-b-PMMAm (2.1b-2.7b) (solid trace).  The new PMPn-b-PMMAm block copolymers, 2.1b-2.7b, were additionally examined using MALDI-TOF MS. The spectrum of PMP15-b-PMMA50 (2.2b) is shown in Figure 2.7 and clearly reveals the expected spacings of 316 g mol-1 due to the PMP segment and 100 amu due to the PMMA segment. Although there is likely fragmentation of the polymer during the analysis,85 ions are observed that may be assigned to species that contain both PMP and PMMA moieties (e.g. 36  n = 11, m = 13 and n = 11, m = 26 in Figure 2.7). For the PMP segment, the ions detected seem to include a molecule of the 2,5-dihydroxybenzoic acid (DHB) matrix. Combined with the monomodal molecular weight distribution determined using GPC, these mass spectrometric data confirm the copolymer structure.   Figure 2.7 MALDI-MS plot of PMP15-b-PMMA50 (2.2b) (n = repeating unit for PMP block, m = repeating unit for PMMA block).  To gain additional insight into the microstructure of these new 2.1b-2.7b block copolymers, we acquired 1H and 13C{1H} NMR spectra along with various two-dimensional spectra of each copolymers. The 1H NMR spectra of purified block copolymers 2.1b-2.7b show all PMP protons ( = 2.0 to CH3;  = 3.4 to CH2;  = 4.7 to CHPh2;  = 7.1 to aryl protons) (as described above) and the new peaks at ( =0.9, 1.0, 1.1 to CH3,  = 1.8 to CH2,  =3.6 to OCH3) 37  can be assigned to protons from PMMA segments, which are consistent with literature record of PMMA.86 As expected, the three signals at approximately 0.9, 1.0 and 1.1 ppm (1H NMR) were observed for the –CH2– moieties of the acrylate repeat unit, which are attribute to syndiotactic (rr), atactic (mr), and isotactic (mm) methyl groups, respectively. Based on the integral of these three peaks (Figure 2.8), the PMMA segment in 2.1b-2.7b were primarily syndiotactic microstructure (55% - 77%) (Table 2.4). Of particular importance are the 13C, 1H HSQC and HMBC NMR spectra of PMP10-b-PMMA10 (2.1b) shown in Figure 2.9, respectively. Perhaps most interesting is that the 13C, 1H HMBC NMR spectrum shows a weak cross correlation between the 1H signal of the –CH2– moiety of PMMA (δ = 1.8 ppm) and the 13C signal assigned to the –CPh2– switching group of the PMP (δ = 51.0 ppm). This 13C weak signal attributed to the –CPh2– appears as a shoulder of the large signal assigned to the o-CH3 moiety (δ = 51.9) and is distinct from the signal assigned to the backbone –CHPh2 groups of the PMP block (δ = 52.7). In addition, the 31P, 1H HSQC NMR spectrum reveals a cross correlation between a –CH2– acrylate moiety (δ = 1.8 ppm) and the phosphorus signal that we tentatively ascribe to the switching group. We note that the o-Me, p-Me and -CH2- moieties of the Mes group have lower field shifts (δ(1H) = 2.0, 3.4 ppm) than previous report homo PMP obtained using free radical initiation.75b Taken together, the GPC, mass spectral and NMR spectroscopic data provides conclusive evidence that a di-block copolymer with the assigned structure 2.1b-2.7b (Scheme 2.3) has been formed.  38   Figure 2.8: 1H NMR of monomer PA, homopolymer PMP and block copolymers PMPn-b-PMMAm (structure shown in Scheme 2.3).  Table 2.4 Tacticity of block copolymer 2.1b-2.7b from Figure 2.8.  Tacticity of PMMA block Composition mm mr rr PMP20    PMP10-b-PMMA10 (2.1b) 24% 21% 55% PMP15-b-PMMA50 (2.2b) 2% 21% 77% PMP15-b-PMMA60 (2.3b) 5% 24% 71% PMP20-b-PMMA20 (2.4b) 14% 27% 59% PMP25-b-PMMA50 (2.5b) 3% 32% 65% PMP25-b-PMMA100 (2.6b) 2% 27% 71% PMP30-b-PMMA100 (2.7b) 6% 22% 72% MP-PMMA400 1% 23% 76% 39   Figure 2.9 1H-13C HSQC, 1H-13C HMBC, 1H-31P HMBC NMR spectrum (400 MHz for 1H, CDCl3, 298 K) of PMP10-b-PMMA10 (2.1b). 40  Interestingly, we postulate that a very similar–CPh2 anion of PMP functions as the initiator in the present case (vide infra). Different from polymerization of 1.1a, –CPh2 anion instead of –CH2 anion in ortho mesityl group of PMP functions initiates the second methyl methacrylate monomers. There are two explanations to rationalize this observation. For bulky monomer 1.1a, the polymerization is hard to propagate by the bulky initiator –CPh2 anion due to the steric hindrance. In this case the proton migration occurs when polymerization of 1.1a. However, for monomer like MMA without steric hinderance, –CPh2 anion as the domain state is preferred to be initiator. Moreover, the polymerization 1.1a conducted at room temperature in polar glyme or THF solvent or at 50 º C in nonpolar toluene solvent with coordinated ligand presence. It provides thermodynamically energy for the deprotonation of o-Me proton. But for the polymerization MMA system, the living anionic polymerization of PMP is cooled down to -78 ºC. While the assumption is made that at low temperatures the PMP polymer favors its kinetic state where the negative charge is delocalized by two phenyl rings, the active chain-end in the ortho-methyl carbanion migrates to diphenyl carbon position. It is then polymerized second MMA monomers forming block copolymer 2.1b-2.7b (Scheme 2.3). The crystallinity of PMPn-b-PMMAm block copolymers 2.5a, 2.2b, 2.5b, 2.6b, PMP1-PMMA400 were studied by X-ray powder diffraction. Because of its lack of complete stereoregularity and bulky side groups, the block copolymers PMPn-b-PMMAm are amorphous (plot is shown in Figure 2.10).  41   Figure 2.10 The crystallinity plot of homo PMMA and PMP polymer and block copolymers PMPn-b-PMMAm measured by Bruker D8-advance X-ray diffractometer.  2.2.4 Other type of poly(methylenephosphine)-block-polyacrylate type polymers To assess the generality of this anionic polymerization, two additional block copolymers were prepared. Both polymers were characterized by 31P, 1H and 13C{1H} NMR spectroscopy which are similar to those described for the aforementioned PMPn-b-PMMAm copolymers. The benzyllithium-initiated polymerization of the xylyl-substituted phosphaalkene 1.1b (15 equiv) followed by the addition of methyl methacrylate (50 equiv) afforded Bn-PMPn-b-PMMAm-H (2.8b). Analysis of the copolymer by GPC-MALS revealed a molecular weight (Mn) of 10,000 Da with a dispersity of 1.07. The chromatogram is shown in Figure 2.11 and reveals a slight shoulder 42  on the low molecular weight end, presumably indicating the presence of a small amount of homo-PMP in the copolymer. A portion of the homo-PMP, removed prior to the addition of MMA, was also analyzed by GPC-MALS (Mn = 4600 Da; Đ = 1.14). These values are consistent with PMP15-b-PMMA53, close to those predicted from the monomer-to-initiator ratio (i.e. PMP15-b-PMMA50). Notably, a small peak is observed with approximately double the molecular weight as PMP15-b-PMMA53. We suspect that this may result from aggregation in solution or some oxidative coupling of the chain ends during quenching.    Scheme 2.4 Synthetic route to PMPn homopolymers (2.8a) and their subsequent block copolymerization via a living anionic polymerization to PMPn-b-PMMAm (2.8b).   Figure 2.11 GPC chromatograms (refractive index traces) collected for homopolymer PMPn (2.8a) (dotted line) and block copolymer PMPn-b-PMMAm (2.8b) (solid line).  43  A second copolymer, Bn-PMP21-b-PtBuA75-H, was prepared from phosphaalkene 1.1a and tert-Butylacrylate (tBA) ([M]:[I] = 20, 75, respectively). Characterization by multinuclear NMR spectroscopy and GPC-MALS supported a block copolymer structure. In particular, the molecular weights and polydispersity of the copolymer (Mn = 16600; PDI = 1.02 for only block copolymer peak) compared to the homopolymer (Mn = 6900; PDI = 1.05) are consistent with PMP21-b-PMMA75. Unfortunately, the GPC trace of the copolymer, shown in Figure 2.12, is bimodal. We speculate that the presence of a significant amount of PMP homopolymer in the copolymer results from the introduction of highly hygroscopic comonomer, tert-butyl acrylate. Despite multiple distillations from CaH2, it was difficult to remove impurities from this monomer.    Scheme 2.5 Synthetic route in block copolymerization of PMP-b-PtBuA (2.9b) by anionic polymerization.  44   Figure 2.12 GPC chromatograms (refractive index traces) collected for homopolymer PMP (2.9a) (dotted line) and block copolymer PMP-b-PtBA (2.9b) (solid line).  2.3 Summary Several new block copolymers have been synthesized from the sequential living anionic polymerization of phosphaalkenes with acrylates. This represents the first synthesis of a functional poly(methylenephosphine)-block-polyacrylate copolymer. Importantly, evidence for the switching groups of the block copolymer was provided from NMR spectroscopic studies. The microstructure of the poly(methylenephosphine) block was also determined and suggests that an addition-isomerization mechanism is predominant for the living anionic polymerization of P-mesityl phosphaalkenes. We have also reported the first measurements of the glass transition of PMP-containing homo- and co-polymers. The present work opens the door to study active PMP initiates olefins, which brought new functionalities into organic macromolecules.   2.4 Experimental section 2.4.1 Materials and general procedures for kinetic study. Toluene was dried over sodium/benzophenone ketyl radical and distilled under reduced pressure and stored over molecular sieves. TMEDA was dried over KOH and freshly distilled before use. secBuLi was purchased from 10 15 20Retention time (min)45  Sigma Aldrich. Mes-P=CPH2 (1.1a) was prepared according to literature procedures.13 All experiments were performed under nitrogen using standard Schlenk technique or in an MBraun (LabMaster) glovebox. 31P NMR (121.5MHz) spectra were record at a series of temperatures 323.15K, 328.15K, 333.15K, 338.15K, 343.15K, 348.15K on a Bruker Avance 400dir spectrometer. Chemical shifts are reported relative to 85% H3PO4 as an external standard (δ = 0.0 ppm for 31P). The delay time (d1) for PMP was set to 10 s. The accuracy of integration in the 31P NMR spectra was controlled by integrating the same region (between 220 - 240 ppm) for the Mes-P=CPh2 monomer and the PMP (between +10 and -40 ppm). Molecular weights were estimated by triple detection gel permeation chromatography (GPC-LLS). Kinetic study of the anionic polymerization of 1.1a. To a stirred solution of 1.1a (0.1 g, 0.32 mmol) in toluene (1 mL) was added a solution of secBuLi (10.40 μL, 14.56 μmol) in toluene (1 mL) with TMEDA (1 drop, ca 0.003mL,0.020mmol) in the glovebox. An aliquot of the reaction mixture was transferred to a NMR tube after stirring for 1 min. The sample was load in the NMR spectrometer at certain temperature from 323.15K to 348.15K. 31P NMR spectra were recorded in every 15 min interval with 72 scans for each spectrum until the polymerization was complete. Two drops of degassed methanol were added to the reaction mixture to terminate the living polymer. After precipitation from concentrated solution mixture with dry hexanes (50 mL) twice, the pale yellow polymer is isolated by filtration and dried in vacuo. The isolated yields are between 40% to 50%. The reproducibility of the kinetic study was confirmed by repeating every experiment twice at each temperature. Refractive index increments of PMPn-b-PMMAm block copolymers. The refractive index increment of a copolymer is a linear function of its composition87 46                                      (d𝑛d𝑐) = 𝑊A (d𝑛d𝑐)A+ 𝑊B (d𝑛d𝑐)B                                                      (1) where (dn/dc)A, (dn/dc)B are the refractive index increments of PMP, PMMA homopolymer respectively and WA, WB are the weight fractions of PMP, PMMA components. The values of (dn/dc)A = 0.2387 and (dn/dc)B = 0.0445 were determined from Cauchy plot. The measurements of Cauchy plots of the polymer solutions were performed by using a Wyatt Optilab T-rEx differential refractometer at λ0 = 658 nm.  2.4.2 Materials and general procedures for synthesis and characterization of homo PMP and block copolymer PMPn-b-PMMAm. All manipulations of air- and/or water sensitive compounds were performed under nitrogen atmosphere using Schlenk line technique or in an MBraun (LabMaster) glovebox. Toluene (Fisher, GR grade) was deoxygenated with nitrogen and dried by passing through a column containing activated alumina, further dried over sodium/benzophenone ketyl and distilled under reduced pressure and stored over activated 4 Å molecular sieves. THF (Fisher, GR grade) was dried over sodium/benzophenone ketyl and distilled under reduced pressure and stored in activated 4 Å molecular sieves. Methanol was degassed prior to use. CDCl3 was purchased from Cambridge Isotope Laboratories Inc. sec-Butyllithium (secBuLi, 1.4 M in cyclohexane) was purchased from Sigma Aldrich used as received. Lithium chloride (LiCl, Alfa Aesar, 99.995%) was dried at 200 ºC under reduced pressure for 2 days. N, N, N′,N′-Tetramethylethylenedi-amine (TMEDA, Alfa Aesar, 99%) was refluxed with KOH, and distilled under nitrogen. Methyl methacrylate (MMA, Aldrich, 99%) was dried over CaH2 overnight and distilled under reduced pressure. It was then titrated with triethylaluminium to a 47  point where the solution turned yellow and freshly distilled under reduced pressure before performing the polymerization. Mes-P=CPh2 (1.1a) was prepared following literature procedure.13 1H, 13C, and 31P NMR spectra were record at 298 K on Bruker Avance 300 or 400 spectrometers. H3PO4 (85%) was used as an external reference (δ = 0.0) for 31P NMR. 1H NMR spectra were referenced to the residual protonated solvent. 13C NMR spectra were referenced to the deuterated solvent. Polymer molecular weights were determined by triple detection gel permeation chromatography (GPC-LLS) using an Agilent liquid chromatograph equipped with an Agilent 1200 series standard autosampler, Phenomenex Phenogel 5 mm narrow bore columns  515 (4.6 x 300 mm) 104 Å (5000-500000 g mol-1) 500 Å (1000-15000 g mol-1), and 103 Å (1000-75000 g mol-1), Wyatt Optilab T-rEx differential refractometer (λ = 658 nm, 40 °C), Wyatt tristar miniDAWN laser light scattering detector λ = 690 nm), and a Wyatt ViscoStar viscometer. A flow-rate of 0.5 mL min-1 was used and samples were dissolved in THF (ca. 1 mg mL-1).  Determine the concentration of Benzyllithium. A modification of the literature procedure to titrate nBuLi was followed.75b To a stirred colorless TMEDA (0.84 mL, 0.65 g, 5.6 mmol) solution in toluene (1000mL), secBuLi solution in cyclohexane (3.12 mL, 1.4 M, 4.37 mmol) was added. The red orange solution was heat at 50 °C for 1 h. Sequently, the solution was cooled to room temperature. Solvent was remove in vacuo. Addition of 50 mL hexanes followed by cooling to -78 °C, resulted in the precipitation of PhCH2Li yellow precipitate. Filtration to isolate the yellow precipitate and further washed twice with 10 mL hexanes at -78 °C. The yellow precipitate was dissolved in THF (20 mL) getting dark red solution of PhCH2Li. It is titrated against N-benzylbenzamide. The concentration was determined to be 0.059M. 48  Preparation of poly(methylenephosphine)-homo-polymers (PMPs) (2.1a-2.7a). All manipulations were performed using standard Schlenk or glovebox technique under nitrogen atmosphere. In a glove box, benzyllithium initiator was prepared by adding secBuLi (1.4 M in cyclohexane) dropwise to a stirred solution of TMEDA dissolved in toluene for 30 mins at 50 °C. The concentration of benzyllithium initiator was subsequently determined by titration following previously reported procedure.2b To the stirred benzyllithium initiator solution at 50 °C was added dropwise 1.1a in toluene. Polymerization progress was monitored by 31P NMR. Upon complete consumption of the 1.1a, aliquots of the reaction mixture were withdrawn and quenched by degassed MeOH for the subsequent characterization of the formed PMP homopolymers (2.1a-2.7a) by GPC and multinuclear NMR spectroscopies.  31P NMR (161.9 MHz, CDCl3, δ): -7.10 (br, s). 1H NMR (400 MHz, CDCl3. δ): 8.06-5.97(br, 12H, m-Mes-H, Ph-H), 5.27-4.06 (br, 1H, -CHPh2), 3.80-3.28(br, 2H, o-CH2), 2.81-0.55 (br, 6H, o, p-CH3), 13C {1H NMR (100.6 MHz, CDCl3, δ):  146.7, 143.1, 138.5, 132.0, 130.5, 129.5, 128.2, 126.0, 124.1-96.9, 51.8, 35.0, 23.5, 20.6. The molecular weight (Mn), molecular weight distribution (Mw/Mn) for 2.1a-2.7a are illustrated in Table 2.1. PMP10 (2.1a): Toluene (1 mL), TMEDA (2 drops, ca 0.009mL,0.060mmol), secBuLi (in 1.4M cyclohexane solution) (31.21 μL, 43.69 μmol) / Mes-P=CPh2 (0.100 g, 0.316 mmol) in toluene (1 mL). Yield=22.5%. PMP15 (2.2a): Toluene (1 mL), TMEDA (2 drops, ca 0.009mL,0.060mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol) / Mes-P=CPh2 (0.150 g, 0.474 mmol) in toluene (1 mL). Yield=31.7%. 49  PMP15 (2.3a): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.060 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol) / Mes-P=CPh2 (0.160 g, 0.506 mmol) in toluene (1 mL). Yield=26.5%. PMP20 (2.4a): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.060 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol) / Mes-P=CPh2 (0.200 g, 0.632 mmol) in toluene (1 mL). Yield=34.1%. PMP25 (2.5a): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.060 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol) / Mes-P=CPh2 (0.260 g, 0.822 mmol) in toluene (1 mL). Yield=37.4%. PMP25 (2.6a): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.060 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol) / Mes-P=CPh2 (0.260 g, 0.822 mmol) in toluene (1 mL). Yield=36.1%. PMP30 (2.7a): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.060 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.290 g, 0.917 mmol) in toluene (1 mL). Yield=40.1%. Preparation of poly(methylenephosphine)-block-poly(methylmethacrylate)s (PMPn-b-PMMAm) (2.1b-2.7b). The PMP carbanion was cooled at -78 °C for 10 mins and LiCl solution in THF was slowly added to the reaction mixture followed by the second monomer, MMA, dissolved in THF. The reaction mixture was stirred at -78 °C then slowly warmed up to room temperature. To remove additives used during polymerization, the product was precipitated with degassed MeOH with vigorous stirring. The white precipitated polymer was filtered, washed with 50  MeOH, and dried in vacuo overnight. The resulting polymers were characterized by GPC and multinuclear NMR spectroscopies. Bn-Mes-P-CPh2-PMMA400: Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.010 mg, 0.032 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL) / MMA (0.10 mL, 0.10 g, 1.00 mmol) in THF (1 mL). Yield=59.1%. 31P NMR (CDCl3, 161.9 MHz, 298 K): δ -0.001 (s); 1H NMR (400 MHz, CDCl3. δ): 3.83-3.24 (br, -OCH3 of the methylmethacrylate), 2.18-1.57 (br, -CH2- of the methylmethacrylate), 1.12 -0.96, 0.96-0.69 (br, -CH3 of the methylmethacrylate ), 13C{1H} NMR (100.6 MHz, CDCl3, δ): 177.80, 176.99, 99.96,51.83, 44.63 The molecular weight (Mn) 42380 g/mol , molecular weight distribution (Mw/Mn) 1.109. PMP10-b-PMMA10 (2.1b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.100 g, 0.316 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL)/ MMA (21.28 μL,20 mg, 0.1998 mmol) in THF (1 mL). Yield=35.8%. PMP15-b-PMMA50 (2.2b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.150 g, 0.474 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL) / MMA (0.11 mL, 0.10 g, 1.0 mmol) in THF (1 mL). Yield=49.6%. PMP15-b-PMMA60 (2.3b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.150 g, 0.474 51  mmol) in toluene (1 mL). // LiCl (0.012 g, 0.28 mmol) in THF (1 mL)/ MMA (0.13 mL, 0.12 g, 1.2 mmol) in THF (1 mL). Yield=56.1%. PMP20-b-PMMA20 (2.4b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.200 g, 0.632 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL)/ MMA (42.55 μL, 40.00 mg, 0.3995 mmol) in THF (1 mL). Yield=39.7%. PMP25-b-PMMA50 (2.5b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.250 g, 0.790 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL)/ MMA (0.11 mL, 0.10 g, 1.0 mmol) in THF (1 mL). Yield=48.2%. PMP25-b-PMMA100 (2.6b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.250 g, 0.790 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL)/ MMA (0.22 mL, 0.20 g, 2.0 mmol) in THF (1 mL). Yield=46.7%. PMP30-b-PMMA100 (2.7b): Toluene (1 mL), TMEDA (2 drops, ca 0.009 mL,0.06 mmol), secBuLi (in 1.4 M cyclohexane solution) (31.21 μL, 43.69 μmol)/ Mes-P=CPh2 (0.300 g, 0.948 mmol) in toluene (1 mL) // LiCl (0.012 g, 0.28 mmol) in THF (1 mL)/ MMA (0.22 mL, 0.20 g, 2.0 mmol) in THF (1 mL). Yield=63.4%. 31P NMR (161.9 MHz, CDCl3, δ): -7.10 (br, s). 1H NMR (400 MHz, CDCl3. δ): 8.14-6.06 (br, m-Mes-H, Ph-H of the methylenephosphine), 5.37-4.12 (br, -CHPh2 of the methylenephosphine), 3.83-3.24 (br, -OCH3 of the methylmethacrylate), 3.24-1.18 (br, o, p-CH3, o-CH2 of the methylenephosphine and -CH2- of the methylmethacrylate), 1.10 -0.93, 0.93-0.09 (br, -CH3 of the methylmethacrylate ), 13C{1H} NMR (100.6 MHz, CDCl3, δ): 148.1-123.7, 54.4, 52  51.9, 44.5, 23.2, 21.1, 18.6, 16.6. The molecular weight (Mn), molecular weight distribution (Mw/Mn) for 2.1b-2.7b are illustrated in Table 2.3. Preparation of poly(methylenephosphine) (PMPn) (2.8a) and poly(methylenephosphine)-block-poly(methylmethacrylate)s (PMPn-b-PMMAm) (2.8b). All manipulations were performed using standard Schlenk or glovebox technique under nitrogen atmosphere. In a MBraun (LabMaster) glove box, secBuLi (62.42 μL, 87.39 μmol, 1.4 M in cyclohexane) dropwise added to a stirred solution of TMEDA (16.77 μL, 13.00 mg, 0.1119 mmol) dissolved in toluene (2 mL) for 30 mins at 50 °C to prepare benzyllithium initiator. Xyl-P=CPh2 (0.300 g, 0.992 mmol) in toluene (2 mL) was dropwise added to the stirred benzyllithium initiator solution at 50 °C. Polymerization progress was monitored by 31P NMR. Upon complete consumption of the Xyl-P=CPh2 (1.1b) aliquots of the reaction mixture were withdrawn and quenched by degassed MeOH for the subsequent characterization of the formed PMP homo-polymers by GPC and multinuclear NMR spectroscopies.  PMP16 (2.8a): 31P NMR (161.9 MHz, CDCl3, δ): -9.33 (br, s). 1H NMR (400 MHz, CDCl3. δ): 8.01-5.86 (br, 13H, m-Xyl-H, Ph-H), 5.12-4.29 (br, 1H, -CHPh2), 3.57-2.99 (br, 2H, o-CH2), 2.99-1.57 (br, 3H, o-CH3), 13C{1H} NMR (100.6 MHz, CDCl3, δ): 146.7, 143.1, 129.5,128.2, 126.0, 51.8, 35.0, 24.6, 23.5. The molecular weight (Mn) is 4899 g/mol, molecular weight distribution (Mw/Mn) is 1.136. The PMP carbanion was cooled at -78 °C for 10 mins and LiCl (0.012 g, 0.28 mmol) solution in THF (1 mL). MMA (0.16 mL, 0.15 g, 1.5 mmol) in THF (1 mL) was then slowly added to the reaction mixture. The reaction mixture was slowly warmed up to room temperature. Polymerization was quenched by degassed MeOH (2 drops). Pump off solvent in vacuum, solid product mixture dissolved in minimum amount THF and then was precipitated with degassed 53  MeOH (50 mL). The white precipitated polymer was filtered, washed with MeOH, and dried in vacuo overnight. The resulting polymers were characterized by GPC and multinuclear NMR spectroscopies. PMP16-b-PMMA35 (2.8b): 31P NMR (161.9 MHz, CDCl3, δ): -9.33 (br, s). 1H NMR (400 MHz, δ): 8.04-6.10 (br, m,p-Xyl-H, Ph-H of the methylenephosphine), 5.14-4.31 (br, -CHPh2 of the methylenephosphine), 3.90-2.98 (br, o-CH2 of the methylenephosphine and -OCH3 of the methylmethacrylate), 2.92-2.16 (br, o-CH3 of the methylenephosphine), 2.09-1.63 (br, -CH2- of the methylmethacrylate), 1.15-0.94, 0.93-0.66 (br, -CH3 of the methylmethacrylate ), 13C APT NMR (100.6 MHz, CDCl3, δ): 178.2, 178.1, 177.9, 177.8, 177.1, 131.5-126.8, 54.5, 54.3, 51.9, 45.0, 44.7, 18.8, 17.6-16.0. CDCl3. The molecular weight (Mn) is 8398 g/mol, molecular weight distribution (Mw/Mn) is 1.121 for 2.8b. Preparation of poly(methylenephosphine) (PMPn) (2.9a) and poly(methylenephosphine)-block-poly(tert-butylacrylate)s (PMPn-b-PtBuAm) (2.9b). In a MBraun (LabMaster) glove box, to the TMEDA (6.45 μL, 5.00 mg, 0.0430 mmol) in toluene (1 mL) solution secBuLi (20.81 μL, 29.13 μmol, 1.4 M in cyclohexane) was added dropwise. Reaction mixture was stirred for 30 mins at 50 °C. Mes-P=CPh2 (0.200 g, 0.632 mmol) in toluene (2 mL) was then dropwise added to the stirred benzyllithium initiator solution. Polymerization progress was monitored by 31P NMR. Once polymerization of the Mes-P=CPh2 was completed, half of the reaction mixture were quenched by degassed MeOH for the subsequent characterization of the PMP homo-polymers by GPC and multinuclear NMR spectroscopies.  PMP25 (2.9a): 31P NMR (161.9 MHz, CDCl3, δ): -9.98 (br, s). 1H NMR (400 MHz, CDCl3. δ): 8.10-5.95(br, 12H, m-Mes-H, Ph-H), 5.25-4.08 (br, 1H, -CHPh2), 3.77-3.21 (br, 2H, o-CH2), 2.91-0.45 (br, 6H, o, p-CH3), 13C{1H} NMR (100.6 MHz, CDCl3, δ): 145.7, 143.5, 138.3, 132.3, 54  130.1, 129.5, 127.2, 126.5, 125.0-96.2, 51.8, 35.3, 24.1, 20.7. The molecular weight (Mn) is 7993, molecular weight distribution (Mw/Mn) is 1.114 for 2.9a. Yield=25.0% The other half of PMP carbanion solution was cooled at -78 °C for 10 mins. LiCl (0.004 g, 0.09 mmol) solution in THF (0.5 mL), tBuA (0.12 mL, 0.090 g, 1.2 mmol) in THF (0.5 mL) was successively added to the reaction mixture. The reaction mixture was stirred overnight and slowly warmed up to room temperature. Polymerization was quenched by degassed MeOH (2 drops). Solvent was pump off under vacuum, solid product mixture was dissolved in minimum amount THF and then was precipitated with degassed MeOH (50 mL) for three cycles. The white precipitated polymer was filtered, washed with MeOH, and dried in vacuo overnight. The resulting polymers were characterized by GPC and multinuclear NMR spectroscopies. PMP25-b-PtBuA48 (2.9b): 31P NMR (161.9 MHz, CDCl3, δ): -9.98 (br, s). 1H NMR (400 MHz, CDCl3. δ): 8.01-5.80 (br, m-Mes-H, Ph-H of the methylenephosphine), 5.49-4.03 (br, -CHPh2 of the methylenephosphine), 3.60-3.31 (br, -CH- of the tert-butylacrylate), 3.27-2.78 (br, o-CH2 of the methylenephosphine), 2.42-1.98 (br, -CH2- of the tert-butylacrylate) 2.00-1.68 (br, o, p-CH3 of the methylenephosphine), 1.64-0.90 (br, CH3 of the tert-butylacrylate), 13C APT NMR (100.6 MHz, CDCl3, δ): 173.7, 144.9-140.1, 139.4-136.0, 132.3-123.3, 79.72, 42.0, 41.5, 35.2, 34.1, 29.7, 28.1, 23.3, 20.9. The molecular weight (Mn) is 13880 g/mol, molecular weight distribution (Mw/Mn) is 1.025 for 2.9b. Yield=43.8% 55  Chapter 3: Attempt to synthesize “masked” phosphaalkenes  3.1 Introduction Masked low-coordinate main-group species have received wide attention for their application in the synthesis of isolable species of transient compounds.88 In the early 1980s, research interest in phosphinidenes (R–P:) was widespread.88 One approach to synthesize phosphinidene was to use 7λ3-phosphanorbornadiene as a precursor. The thermolysis of 7λ3-phosphanorbornadiene could easily eliminate the phosphorus bridge, thus producing a phosphinidene as shown in Scheme 3.1. The aromaticity of the benzene byproduct is regarded as the driving force for the decomposition.   Scheme 3.1 Thermal decomposition of 7λ3-phosphanorbornadiene.  However, it was quite challenging to synthesize 7λ3-phosphanorbornadienes due to their instability resulting from the unprotected lone electron pair at phosphorus and its inherently strained structure.89 For a long time, the only established protocol to access 7λ3-phosphanorbornadienes required multiple steps starting with the [2 + 4] cycloaddition of electrophilic acetylenic dienophiles and phospholes.90 In 1984, Matsumoto et al. tried to increase the stability of 7λ3-phosphanorbornadiene by oxidizing it to a 7λ3-phosphanorbornadiene phosphine-oxide.91 Unfortunately, the instability issue remained. Following this discovery, Stille et al.92 and Kashman et al.93 successfully synthesized 56  the first stable 7λ3-phosphanorbornadiene phosphine oxide 3.1a. However, the phosphorus bridge of 3.1a collapsed during an attempted reduction of the P=O moiety. Mathey and Maritti developed an alternative strategy to obtain stable 7λ3-phosphanorbornadienes by complexing the phosphorus bridge to a metal 3.1b.94 It was assumed complexes 3.1b could decompose by the cheletropic elimination of metal carbonyl-stabilized phosphinidine :P(R)M(CO)5. However, a decomposition occurred during the decomplexation of 3.1b without generating the desired 7λ3-phosphanorbornadiene.   Figure 3.1 Stabilized 7λ3-phosphanorbornadiene species.  In 2012, a huge breakthrough was achieved by Cummins and coworkers who discovered that the stable unprotected dibenzo-7λ3‑phosphanorbornadiene could be isolated following reaction of magnesium anthracene (MgA۰3THF) with phosphorus chloride (Scheme 3.2).95 Moreover, this synthetic route is much simpler than the traditional [2 + 4] Diels–Alder cyclization, since it is a one-step reaction. This synthetic method of salt metathesis of an anthracenide salt with RXCl2 has been successfully employed for other inorganic element, such as silicon (X=Si)96 and germanium (X=Ge)97.  57   Scheme 3.2 General procedure to synthesize unprotected 7λ3‑phosphanorbornadiene derivatives (R = tBu, dbabh, HMDS, iPr2N).  This type of salt metathesis reaction can be used to access numerous low-coordinate 8-heteroatom-norbornadiene species as well. It is worth noting that Roark and Peddle at University of Alberta reported the stable “masked” disilene compound 3.2 (Scheme 3.3a) in 1972.98,99 Much later, it was found that 3.2 could be used for anionic polymerization to provide a novel method for preparing polysilane (3.2-P) as shown in Scheme 3.4.100 And recently, Cummins’ group successfully synthesized “masked” digermene 3.3, that potentially is a suitable monomer for polygermane (Scheme 3.3b).97-98   Scheme 3.3 Synthesis of a) dibenzo-7,8-tetramethyldisilabicyclo[2.2.2]octadiene (3.2) and b) dibenzo-7,8-tetramethyldigermabicyclo[2.2.2]octadiene (3.3).97-98  58    Scheme 3.4 Anionic polymerization of 3.2.  The only account of substituted 2-phosphabicyclo[2,2,2]octa-5,7-dienes 3.4 is a report from Quin’s group that was published in 1987.101 Their synthetic approach (Scheme 3.5), albeit elegant, employs a [2 + 4] cycloaddition and involves 10 steps, making it challenging and inefficient.102   Scheme 3.5 Synthesis of 2-phenyl-2-phosphabicyclo[2,2,2]octa-5,7-diene developed by Quin’s group.  Our group was motivated to develop a simple and practical route to a “masked” phosphaalkenes, such as 3.4, for application as a monomeric precursor to new functional polymers. The proposed methodology is shown in Scheme 3.6 and involves the salt elimination reaction of 59  MgA۰3THF with a substituted chloro(chloromethyl)phosphine to ideally generate a “masked” phosphaalkene. Presumably, such a “masked” phosphaalkene might be directly polymerizable using anionic methods of initiation, leading to the formation of PMP. It is expected that this method might overcome the difficulties in accessing phosphaalkene monomers bearing smaller substituents than P-Mes and C-Ph.   Scheme 3.6 Postulated synthetic route to “masked” phosphaalkene and its potential application in anionic polymerization.  3.2 Results and discussion 3.2.1 Synthesis of dichloro(chloromethyl)phosphine (3.7) Compound 3.5 was prepared from CH2Cl2 and PCl3 in presence of AlCl3, following the method of Kinnear and Perren, yield 37%.103 Compound 3.6 was obtained by treating 3.5 with P4S10 following the method of Schmutzler, yield 92%.104 Compound 3.7 was synthesized using modified literature procedures to achieve higher yield by the reduction of Compound 3.6 with dichlorophenylphosphine (Scheme 3.7). This reduction step was an equilibrium reaction. Thus, the reaction mixture was comprised of both reactants and products, from which 3.7 was isolated by distillation (b.p. 30 ºC at 1 Torr). However, trace amounts of PCl3 byproduct were collected with 3.7, which required a follow up distillation at atmospheric pressure under N2 with a bath 60  temperature at 140 ºC to afford pure 3.7 (b.p. 125 ºC at 760 Torr) in 47% overall yield. The 31P NMR spectrum shows a peak at 159.2 ppm. 1H NMR spectrum shows a doublet at 4.10 ppm with coupling constant (2JPH) 16 Hz, which can be assigned to CH2 protons. 13C{1H} NMR spectrum displays a doublet at 48.2 ppm with coupling constant (2JPC) 55 Hz. Giving 31P, 1H and 13C{1H} NMR spectroscopic data that are consistent with literature report, the assignment of the product as 3.7 was confirmed.105   Scheme 3.7 Synthetic route to 3.7.  3.2.2 Synthesis of (chloromethyl)mesitylphosphinyl chloride (3.8a) It has previously been shown that the reaction of perfluoroalkyl Grignard reagents (RfMgBr) with phosphorus(III) halides (PX3) is an efficient, high yielding procedure for the synthesis of (perfluoroalkyl)phosphonous dihalides (RfPX2).106 For the present study, equimolar amounts of 3.7 and mesityl Grignard reagent (MesMgBr) were reacted at -78 °C in THF solution for 4 h (Scheme 3.8). After the reaction mixture had warmed to ambient temperature, an aliquot was removed from reaction mixture. Two singlets at δ = 74.9 and δ = 60.3 were observed that were tentatively assigned to MesPClCH2Cl (3.8a) and MesPBrCH2Cl (3.8b), respectively (Figure 3.2a). The MgBrCl salt was removed by filtration using hexane.  The substitution reaction of the mixture of 3.8a/3.8b was performed using tetrabutylammonium chloride (TBACl) in THF solution at ambient temperature. It was completed 61  within 10 mins (Scheme 3.8). A singlet was observed at δ = 74.9 in the 31P NMR spectrum (Figure 3.2b) suggesting that all bromo substituents were replaced by the chloro. After concentrating the THF solution, pure 3.8a was isolated by extraction into hexane in 57% overall yield. Literature reports compounds of the type ClC-PArCl (Ar = C6H5, 2,4,6-iPr3C6H2, 2,4,6-tBu3C6H2) having chemical shifts at δ= 71.5, δ= 70.5, δ= 67.5 in 31P{1H} NMR spectra, respectively.107.    Scheme 3.8 Synthetic route to 3.8a.           Figure 3.2 31P NMR spectrum (CDCl3, 161.9 MHz, 298 K) a) of product mixture 3.8a/b when 3.7 reacts with MesMgBr; b) after treating 3.8a/b with TBACl. 74.9 60.3 74.9 a b 62  1H NMR spectrum of 3.8a is shown in Figure 3.3, signals are observed at 2.3 ppm, 2.7 ppm, 4.2/4.3 ppm and 6.9 ppm which were assigned to the protons from p-CH3, o-CH3, methylene and aryl group, respectively. Of particular interest are the two diastereotopic protons of the methylene group (δ1H = 4.2 and 4.3) splitting into a doublet of doublets with a coupling constant (2JHH) 11.2 Hz in the 1H{31P} NMR spectrum. These two protons also exhibited a coupling to phosphorus with a 2JPH of 8.4 Hz (δ1H = 4.3) and 12.9 Hz (δ1H = 4.2). The diastereotopic protons of the -CH2- group of compounds ClCH2-PRCl (R = C6H11, R=secC4H9) have been observed previously.107 The 2D HSQC {1H, 13C} spectrum (Figure 3.4) of compound 3.8a was also used to assign all the carbon peaks and further confirms the identity of 3.8a. An EI-MS spectrum of this compound revealed a major signal at 234 g mol-1 that was assigned to 3.8a. In this case, we can infer that 3.8a was formed.   Figure 3.3  1H NMR spectrum (400 MHz for 1H, CDCl3, 298K) of 3.8a. 63   Figure 3.4 1H-13C HSQC spectrum (400 MHz for 1H, CDCl3, 298K) of 3.8a. The ordinate shows the 13C{1H} NMR spectrum and the abscissa shows the 1H NMR spectrum.  3.2.3 Synthesis of benzyl(mesityl)(phenyl)phosphane (3.10) A reactivity study of 3.8a with magnesium reagent was conducted by treating 3.8a with phenyl Grignard reagent (Scheme 3.9). At first 3.8a in THF solution was treated with PhMgBr (1 equiv). An aliquot was removed from the reaction mixture which showed a singlet at -16.7 ppm in 31P NMR spectrum. This chemical shift is similar to δ31P = -11 of the known compound, Ph2PCH2Cl.108 The 1H NMR shows chloromethyl (-CH2Cl) protons at 3.4 ppm, o-methyl protons at 2.6 ppm and p-methyl protons at 2.4 ppm with relative integrated intensities of 2:6:3. The 64  product was assigned to compound 3.9. Then 3.8a in THF solution was treated with 2 equiv of PhMgBr. The progress of substitution was monitored by 31P NMR spectroscopy. After 30 minutes the spectrum revealed two sharp resonances at -16.7 and -18.8 ppm (Figure 3.5a) which were assigned to 3.9 and 3.10, respectively.109 After additional 15 hours at ambient temperature the sharp resonance at -16.7 ppm disappeared leaving 3.10 as the sole product (Figure 3.5b). The reaction residue was dried in vacuo and dissolved in EtOH solution forming suspension. Filtration the reaction mixture and collected filtrate. The solvent was removed in vacuo yielding a white solid. The 1H NMR spectrum in CDCl3 shows signals that can be assigned to compound 3.10. Two singlets at 2.20 ppm and 2.28 ppm were assigned to o-CH3 and p-CH3 protons respectively. Two doublet of doublets at 3.55 ppm and 3.65 ppm with a coupling constant (2JHH) of 13.3 Hz was corresponding to the diastereotopic protons of the -CH2- group and the aryl protons are observed at 6.88 ppm and 7.29 ppm. The EI-MS spectrum shows a major signal at 318 g۰mol-1 that was assigned to 3.10. All 31P, 1H and 31C{1H} data are consistent with literature record of compound 3.10. 110 Spectroscopic results suggest that the chlorine atoms attached to phosphorous and to carbon can be replaced by phenyl groups under the aforementioned conditions. However, the rate of substitution of the chlorine atoms on carbon is considerably slower than that on phosphorus atoms.   Scheme 3.9 Synthesis of benzyl(mesityl)(phenyl)phosphane 3.10.   65            Figure 3.5 31P NMR spectrum (161.9 MHz, CDCl3, 298 K) of an aliquot removed from the reaction mixture after PhMgBr (2 equiv) was added into 3.8a and stirred for a) 30 mins, b) 15 hours.   3.2.4 Preliminary results in the synthesis of “masked” phosphaalkenes The reaction of 3.8a with magnesium anthracene (MgA۰3THF) is of interest as a potential synthetic route to “masked” phosphaalkenes. The proposed synthetic route is shown in Scheme 3.10a. MgA۰3THF (1 equiv) was added in portions over 3 hours to the solution of 3.8a (1 equiv) in THF at –78 ºC. After 2 h the color of the reaction mixture slowly changed from colorless to yellow, eventually turning dark blue-green after 9 h at -78 ºC. A further color change from orange to pale yellow was observed when the reaction mixture was slowly warmed to ambient temperature. Analysis of an aliquot using 31P NMR spectroscopy showed a sharp singlet at –42.2 ppm and broad resonance at –20 to -50 ppm (Figure 3.6a). A yellow colored residue was collected a b 66  after removing solvent in vacuo. It could be further extracted into diethyl ether solution to remove the magnesium salt.   Scheme 3.10 a) Proposed reaction of synthesis compound 3.11, b) rationalization of the reaction process leading to the formation of 3.13.  67   Figure 3.6 31P NMR spectrum (161.9 MHz, CDCl3, 298 K) of a) crude reaction mixture of products of MgA۰3THF with 3.8a/b, b) fraction 2 after purification by column chromatography, c) fraction 3 after purification by column chromatography.  To analyze the product mixture, attempts were made to separate and isolate the component through chromatography using hexane:ethyl acetate (1:1) as eluent under aerobic condition. There were three fractions. The first fraction, anthracene (Rf = 0.82), was identified by using 1H NMR spectroscopy and ESI-MS. Fortuitously, single crystals were obtained of the solid residue left upon rotoevaporating the solvent from the second fraction (Rf = 0.097) by slow diffusion of hexanes into a MeOH solution. Analysis of the crystals using 31P NMR spectroscopy showed a single resonance at 29.1 ppm in (Figure 3.6b). Surprisingly, analysis of the crystals by X-ray crystallography permitted it to be identified as compound 3.13 (Figure 3.7). Formation of 3.13 could be caused by ? ?  3.12 3.13 ? 68  rearrangement and subsequent oxidation of compound 3.11. Unfortunately, we were unable to isolate enough 3.13 to enable further investigations, such as comparing resonances in the 31P NMR spectrum of 3.12 with the 31P NMR spectrum of the crude reaction mixture as shown in Figure 3.6a.   Figure 3.7 Molecular structure of 3.13 by ORTEP 3. Ellipsoids are drawn at the 50% probability level; hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (º): P(1)–O(1) 1.49760(8), P(1)–C(3) 1.83934(14), P(1)–C(1) 1.85179(16), P(1)–C(2) 1.80633(13), O(1)–P(1)–C(3) 71.769(6), O(1)–P(1)–C(1) 115.491(4), O(1)–P(1)–C(2) 108.799(5), C(3)–P(1)–C(2) 114.375(2), C(2)–P(1)–C(1) 100.973(3), C(1)–P(1)–C(3) 109.044(3).  The third fraction (Rf = 0) had resonances ranging from 30 ppm to 70 ppm of the 31P NMR spectrum. The 31P resonances were tentatively assigned to the oxidized oligomers resulting from intermolecular reactions of mesitylphosphaalkene (Mes-P=CH2), the decomposition product of P1 O1 C1 C2 C3 69  3.11. GPC-MALS analysis (Figure 3.8) showed that small molecules with Mn = 627 g mol-1 are the main component in the third fraction. The previous report from Quin et al. mentioned that phenylphosphaalkene (Ph-P=CH2) that formed from the decomposition of 3.2 underwent intermolecular reactions to give a product mixture from head-to-head or head-to-tail oligomerization reactions with broad 31P NMR signals at –40 to –50 ppm in the CDCl3 at ambient temperature.14   Figure 3.8 GPC chromatogram (refractive index traces) collected for third fraction.  An alternative experimental proof of the existence of 3.11 was using a diene such as 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene as a trapping reagent. In this case, the controlled experiments had been conducted by adding the trapping reagent 1,3-cyclohexadiene to the reaction mixture of MgA۰3THF and 3.8a (Scheme 3.11). 31P NMR spectroscopy was used to monitor the reactions. A new signal appeared at –17.3 ppm when 1,3-cyclohexadiene was added (Figure 3.9b). This new signal was tentatively assigned to 3.14. The chemical shift of compounds 3.15 and 3.16 (Figure 3.10) in the 31P NMR spectrum appear at –47.0 ppm and –29.3 ppm, respectively.14 An 17 19 21 23 25 27Retention time (min)70  ESI-MS spectrum of this mixture shows an ion at 244 g mol-1 [M+] which was tentatively assigned to 3.14.   Scheme 3.11 Reaction of MgA۰3THF and 3.8a with 1,3-cyclohexadiene as trapping agent added after 9 hours.   Figure 3.9 31P NMR spectrum (CDCl3, 161.9 MHz, 298 K) from an aliquot of the reaction mixture of a) MgA۰3THF with 3.8a, b) MgA۰3THF with 3.8a and 1,3-cyclohexadiene after 9 h.   Figure 3.10 Structures of 2-methyl-2-phosphabicyclo[2.2.2]oct-5-ene (3.15)  and 2-phenyl-2-phosphabicyclo[2.2.2]oct-5-ene (3.16).111 71  3.3 Summary The preliminary results of a study to develop a convenient route to the “masked” phosphaalkene 3.11 have been discussed. Compound 3.13 could be isolated and characterized by X-ray crystallography. The 1,3-cyclohexadiene was added into the reaction of MgA 3۰ THF with 3.8a to trap 3.11. Further studies are still required to fully understand this reaction process such as a deuteration experiment.  3.4 Experimental section Materials and General Procedures. All manipulation of air and/or water sensitive materials were conducted under nitrogen using Schlenk line techniques or in an Innovative Technology glovebox. Phosphorus trichloride (Sigma Aldrich), aluminum chloride (Acros Organics), phosphorus pentasulfide (Acros Organics), dichlorophenylphosphine (Sigma Aldrich), magnesium (Fisher Science Education), 2-bromomesitylene (Alfa Aesar), lithium (Sigma-Aldrich), and cyclohexadiene (Sigma Aldrich) were used as received. Tetrabutylammonium chloride (Sigma Aldrich) was recrystallized from acetone by addition of diethyl ether and further dried in vacuo. Anthracene (Sigma Aldrich) was sublimed before use. Biphenyl (Sigma Aldrich) was recrystallize from EtOH followed by vacuum sublimation. THF was freshly distilled from sodium/benzophenone ketyl before use. Dichloromethane and hexanes were dried by passing through column of activated alumina. CDCl3 and CD2Cl2 were purchased from Cambridge Isotope Laboratories Inc. MgA·3THF (A = anthracene) was prepared following literature procedures.112 Compound 3.6 was synthesized following known literature procedures.105, 113 72  1H, 31P, 13C NMR spectra were recorded on Bruker Avance 300 MHz or 400 MHz spectrometers. Chemical shifts are reported relative to residual CHCl3 (δ = 7.26 for 1H and δ = 77.23 for 13C). 85% H3PO4 was used as external standard δ = 0.0 for 31P.  Synthesis of compound (3.7). PhPCl2 (8.99 g, 50.2 mmol) was added to 3.6 (8.01 g, 43.7 mmol) at 175 ºC with vigorous stirring, the color of solution changed from colorless to light yellow after 7 hours. Compound 3.7, with PCl3 as minor impurity, was isolated by reduced pressure distillation of the reaction mixture using water pump (1.0 Torr) and heating by oil bath (T = 40-80 ºC). The product was collected in a Schlenk flask cooled by liquid nitrogen. Following atmospheric pressure distillation of 3.7 (b.p. 125 ºC) under nitrogen at 140-145 ºC to get rid of the first few drops of PCl3 impurity. Yield= 47.2 % 31P NMR (161.9 MHz, CDCl3, 298 K): δ 159.2 (s); 1H NMR (400.1 MHz, CDCl3, 298 K): δ 4.10 (d, 2JPH = 16.0 Hz, 2H, -CH2-); 13C{1H} NMR (100.6 MHz, CDCl3, 298 K) δ 48.2 (d, 2JPC = 55.8 Hz, 2H, -CH2-). Synthesis of compound (3.8a). To a stirred suspension of activated Mg (0.98 g, 40.4 mmol) in THF (25 mL) was added bromomesitylene (5.06 mL, 33.1 mmol) dropwise. The reaction was monitored by 31P NMR spectrometry. After refluxing for 2 hours, the Grignard reagent was formed as evidenced by the deep brown color. It was cannula-transferred into a THF solution of 3.7 (4.17 g, 27.6 mmol) (25 mL) dropwise at -78 ºC. The reaction mixture was warmed back up to room temperature and the solvent was removed in vacuo, leaving a yellow oil. To the yellow oil was added hexanes (3 × 10 mL) and the suspension was filtered, and the solvent was removed in vacuo to obtain a light-yellow oil of 3.8a/b. Yield=75.6%. To a stirred solution of 3.8a/b (0.50 g, 1.9 mmol) dissolved in THF (5 mL) was added dropwise tetrabutylammonium chloride (0.60 g, 2.2 mmol) in THF (5 mL). After vigorous stirring 73  for 10 min, the solvent was removed in vacuo, leaving a pale yellow colored residue. To the residue was added hexanes (3 × 3 mL) and the suspension was filtered, and the solvent removed in vacuo. The pure 3.8a was isolated. Yield=57.1%. 31P NMR (161.9 MHz, CDCl3, 298 K): δ 74.9 (s); 1H NMR (400.1 MHz, CDCl3, 298 K): δ 6.9 (s, 2H, aryl H), 4.3 (dd, 2JHH = 11.2 Hz, 2JPH = 8.4 Hz, 1H, -CH2-), 4.2 (dd, 2JHH = 11.2 Hz, 2JPH = 12.9 Hz, 1H, -CH2-), 2.7 (d, 4JPH = 2.45 Hz, 6H, o-CH3), 2.3 (s, 3H, p-CH3); 13C NMR (100.6 MHz, CDCl3, 298 K): δ 144.1 (s, aryl C), 143.9 (s, aryl C),141.7 (s, aryl C), 130.3 (s, aryl C), 130.1 (s, aryl C), 127.0 (s, aryl C), 126.3 (s, aryl C), 42.4 (d, 1JPC = 41.5 Hz, -CH2-), 22.4 (d, 2JPC = 21.5 Hz, o-CH3), 21.5 (s, p-CH3); MS (EI) : m/z= 236, 234 [60, 100, M+]. Synthesis of compound (3.10). To a stirred suspension of magnesium (0.05 g, 2.1 mmol) in THF (10 mL) was added dropwise bromobenzene (0.30 g, 1.9 mmol). The reaction mixture was refluxed at 75 ºC for 2h. This freshly made Grignard reagent was added dropwise to the 3.8a (0.19 g, 0.80 mmol) dissolved in THF (5 mL) at -78 ºC. The reaction was monitored by 31P NMR spectroscopy. Light yellow solution slowly turned to colorless after stirring for 15h. The solvent was removed in vacuo, leaving a white residue. The residue was dissolved in degassed EtOH (3 × 5 mL) and the suspension was filtered. The solvent was removed in vacuo leaving white solid product. Yield=37%. 31P NMR (161.9 MHz, CDCl3): δ -18.8 (s); 1H NMR (400.1 MHz, CDCl3): δ 7.29-7.19 (m, 10H, aryl H), 6.88 (s, 2H, Mes), 3.65 (dd, 2JHH = -13.3 Hz, 2JPH = 3.1 Hz, 1H, -CH2-), 3.55 (dd, 2JHH = -13.4 Hz, 2JPH = 3.4 Hz, 1H, -CH2-), 2.28 (s, 3H, p-CH3), 2.20 (s, 6H, o-CH3);13C NMR (100.6 MHz, CDCl3): δ 145.0 (s, aryl C),141.5 (d, 2JPC= 16.9 Hz, aryl C), 137.1 (d, J= 10.8 Hz, aryl C), 129.5 (s, aryl C), 129.4 (s, aryl C), 129.1 (s, aryl C), 129.0 (s, aryl C),128.9 (s, aryl C), 74  128.3 (s, aryl C), 128.2 (s, aryl C), 126.5 (s, aryl C), 125.9 (s, aryl C), 33.8 (d, 1JPC = 18.4Hz, -CH2-), 23.2 (s, o-CH3), 23.1 (s, o-CH3), 21.0 (s, p-CH3); MS (EI): m/z 319, 318 [39, 100, M+]. Synthesis of compound (3.13). To a stirred solution at -78 °C of 3.8a (0.2 g, 0.85 mmol) dissolved in THF (10 mL) was added MgA۰3THF (0.36 g, 0.85 mmol) orange powder in small portions. The color of the solution gradually changed from colorless to yellow to eventually dark blue-green after 9 hours. The reaction was monitored by 31P NMR spectrometry. After 9 h the reaction was completed and slowly warmed back up to ambient temperature. The solution color went from dark blue-green to yellow. The reaction mixture was filtered to remove the black solid precipitate. The solvent was removed in vacuo, leaving a yellow solid. Diethyl ether (5 mL) was used to extract product mixture. The resulting yellow solution with white suspension was filtered and the solvent was removed from filtrate in vacuo. The product mixture was dry-loaded onto a silica-gel column. A 1:1 mixture of hexanes-ethyl acetate (EA) was used as an eluent. The first fraction of colorless solution was dried in vacuo. Second collected fraction was a yellow solution with bright light blue fluorescence under UV light. The third fraction was collected as a yellow solution. All Rf value was calculated from mixture of compound separated in 1:1 mixture of hexanes- EA. Fraction 1 was identified as anthracene. 1H NMR (400.1MHz, CDCl3, 298K): δ 8.4 (s, 2H, aryl H), 8.0 (dd, 4H, aryl H) 7.5 (dd, 4H, aryl H). MS (ESI): 179, 178 [15, 100, M+]. Yield=0.25g (83.1%) Rf=0.82 Fraction 2 was identified as anthracen-9-yl(mesityl)(methyl)phosphine oxide (3.14). Single crystals suitable for X-ray diffraction analysis of second fraction were obtained by slow diffusion of equal amount of hexane into product in MeOH solution. Yield=0.028g (9.3%); Rf = 0.097. 31P NMR (161.9MHz, CDCl3, 298K): δ 29.1 (s); 1H NMR (400.1MHz, CDCl3, 298K): δ 9.0 (dd, 2H, 75  aryl H), 8.6 (s, 1H, aryl H), 8.0 (dt, 2H, aryl H), 7.4 (m, 4H, aryl H), 2.4 (d, 3H, 2JPH = 12.9 Hz, -CH3), 2.3(s, 6H, o-CH3), 2.2(s, 3H, p-CH3). Fraction 3 was suspected as oxidized oligomers of Mes-P=CH2. 31P NMR (CDCl3, 161.9MHz, 298K): δ 46.9 (br); Rf = 0. GPC analysis shows peak 1 with Mn = 627, Đ = 1.89, Mass fraction: 98.2%; peak 2 with Mn = 1655, Đ = 1.04, Mass fraction:1.6%; peak 3 with Mn = 7410, Đ = 1.12, Mass fraction: 0.2%.   76  Chapter 4: Overall Conclusions and Future Work  4.1 Summary of thesis work In Chapter 2, a new type of phosphaalkene-based block copolymer PMPn-b-PMMAm has been successfully synthesized following Scheme 2.3. This is the first time that the PMP anion has been employed as an macroinitiator to polymerize a second monomer. It widens the scope of potentially obtainable PMP-containing block copolymers. The kinetic study of the polymerization Mes-P=CPh2 in nonpolar solvent, toluene, in presence of a coordinating ligand, TMEDA, yielded activation energy (Ea) of 16.7 ± 0.7 kcal۰mol-1. Compared with the known system for anionic polymerization Mes-P=CPh2 (glyme solution) where the Ea was calculated to be 14.0 ± 0.9 kcal۰mol-1,14 the activation barrier is not much larger for the polymerization in nonpolar toluene/TMEDA system. This finding provides more solvent options for anionic polymerization of Mes-P=CPh2. NMR, GPC, MALDI-TOF MS and XRPD were used to fully characterize PMPn-b-PMMAm block copolymers. The morphology of block copolymers 2.1b-2.7b were determined by XRPD.    Scheme 2.3 Synthetic route to block copolymerization via a living anionic polymerization to PMPn-b-PMMAm (2.1b-2.7b). 77  In chapter 3, a facile route was studied in synthesis of substituted 2-phosphabicylco[2,2,2]octa-5,7-dienes (3.11) through the reaction of 3.8a and MgA۰3THF. The modified reaction process is slowly mix MgA۰3THF powder with 3.8a and keep the reaction temperature below -78 ºC. Once the reaction is complete (9 hours) monitoring by 31P NMR spectroscopy, the reaction vessel is gradually warmed back to room temperature. Unexpectedly, after the purification process through column chromatography under air, the mixture of anthracene, 3.13 and tentatively assigned oligomers were isolated. The desired compound 3.11 cannot be obtained directly probably due to its instability and/or thermal degradation. However, the formation of 3.13 suggests 3.11 may be formed during the reaction.    Scheme 3.10 a) Proposed reaction of synthesis compound 3.11, b) rationalization of the reaction process leading to the formation of 3.13. 78  4.2 Future work The successful synthesis of PMP-b-PMMA block copolymers provides an opportunity to form ordered nanoparticles based on the possible self-assembly properties of block copolymers in block selective solvents. By tuning the polymer-solvent interactions polymer microstructures such as micelles, vesicles, might be accessible. Previous studies implied that PMP is a good coordinating ligand for gold(I) ions.76 The formation of PMP۰AuCl-b-PMMA nanoparticles is promising and has potential application as a catalyst. Moreover, metal coordinated phosphaalkene-based block copolymers would be of future interest because of their potential applications as polymer supported catalysts. Moreover, it is well known that the PMMA segment can undergo acid-catalyzed hydrolysis into polyacrylic acid (PAA).114 Thus, hydrolysis of PMP-b-PMMA into PMP-b-PAA (Scheme 4.1) would represent a new pathway to design hydrophilic macromolecules that could be explored as potential carriers for drug delivery. Recent study also reports that PAA copolymers have an antimicrobial effect. Due to the negatively charged surface it delays bacterial attachment and biofilm formation.115    Scheme 4.1 Proposed mechanism of hydrolysis PMP-b-PMMA to PMP-b-PMAA.  79  What’s more, various building blocks are possible to construct phosphaalkene-based block copolymers, for example, polyphosphaalkene-block-polysiloxane and polyphosphaalkene-block-polysilane (Figure 4.1). These new type of inorganic block copolymers may be good candidates for electronic applications and such investigations might be explored as future work.   Figure 4.1 Proposed structures of poly(methylenephosphines)-block-poly(dimethylsiloxane) PMP-b-PDMS and poly(methylenephosphines)-block-poly(dimethylsilene) PMP-b-PSi.  To solve the instability problem of “masked” phosphaalkene 3.11 there are diverse ways worth to pursue. Considering the fact that compound 3.4 is unstable at ambient temperature found by Quin et al (Figure 4.2), in contrast, 4.1 is reasonably stable, which eliminates phosphaalkene at 40 ºC in toluene after 5 hours.14 It is possible that shrinking the size of group attached on phosphorous atom from phenyl group to methyl group could minimize the effect of steric repulsion. And the electron withdrawing group on mask could also help to stabilize compound 4.1.  80   Figure 4.2 2-Phenyl-2-phosphabicyclo[2.2.2]octa-5,7-diene (3.4) and 2-methyl-2-phosphabicyclo[2.2.2]octa-5,7-diene-5,6-dicarboxylic acid (4.1) are reported by Quin’s group.  In our case, in order to stabilize 3.11 decrease the size of group (eg: Xyl, Ph, Me and etc) attached on phosphorous is appropriate. Also, employing an electron deficient mask can be considered, such as dimethyl phthalate, in terms of stabilizing the lone pair electrons on phosphorous. The ultimate goal is to synthesize the stable “masked” phosphaalkenes that could either eliminate phosphaalkene upon heating or directly act as a source of P=C monomers for polymerization (Scheme 4.2). Ideally, these prospective monomers would be used to grow polymers containing an alternating P-C backbone.    Scheme 4.2 Proposed anionic polymerization reaction of substituted 2-phosphabicylco[2,2,2]octa-5,7-dienes.  4.3 Closing remarks The research work included in this thesis expands the family of phosphaalkene-based block copolymers. The successful synthesis of PMP-b-PMMA broadens this field in developing PMP initiated block copolymers. It builds our confidence in forming various composition of phosphaalkene-based block copolymers. Concomitantly, the search for a new type of stable phosphaalkene monomer was explored. Given that the phospha-Peterson route of synthesis 81  phosphaalkene bearing smaller groups often leads to dimerization or polymerization problems, we designed an entirely new synthetic strategy. Our new approach involved preparing “masked phosphaalkene” compounds and the results obtained look promising to solve both stability and polymerization problems. In this study, we discovered that phosphaalkenes may be formed as transient species. Further studies exploring the way to stabilize this transient phosphaalkene are required. The successful synthesis of stable phosphaalkenes will continue be the target of research in our group and the work outlined in this thesis has helped to take this project a small step further. 82  References  1. Wu, G. Amino acids: Biochemistry and nutrition; CRC Press Boca Raton, 2013. 2. Thinius, K. Studies on the history of plastics. 20. Development and use of non-polar polymer mixtures from polystyrene and elastomers, especially natural-rubber. 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Positively charged biomaterials exert antimicrobial effects on gram-negative bacilli in rats. Biomaterials 2003, 24 (16), 2707-2710.  101  Appendices  Appendix A  The determination of the dn/dc of PMP20-b-PMMA20 (2.4a)    Figure A.1 Cauchy plot of differential refractive index vs concentration of PMP20-b-PMMA20 in THF (measured on Wyatt Optilab T-rEx refractive index detector). The slope (0.1897) is used to determine dn/dc.   Determine dn/dc from RIFit R²=0.9988data fitConcentration (g/mL)0.000 0.001 0.002 0.003 0.004 0.005 0.006differential refractive index0.00000.00050.0010102  Appendix B  Monomer conversion data collected for the polymerization of 1.1a in Toluene/TMEDA system  Table B.1. Monomer conversion data collected for the polymerization of 1.1a using 4% BnLi as initiator in toluene and TMEDA solvent system at T = 325.2K. Entry Percent conversion determined by 31P NMR [M]a mol L-1 In[M]0/[M] Time (h) 1 0.0476 0.196667 0.048790164 0.5 2 0.0909 0.187727 0.09531018 1 3 0.2857 0.1475 0.336472237 1.5 4 0.4171 0.120373 0.539704583 2 5 0.4902 0.105271 0.673760467 2.5 6 0.6000 0.0826 0.916290732 3 7 0.6875 0.064531 1.16315081 3.5 8 0.8431 0.032405 1.851976165 4 9 0.9091 0.018773 2.397895273 4.5 10 0.9420 0.011984 2.846733301 5 11 0.9607 0.008123 3.235544134 5.5 12 0.9652 0.007196 3.356796072 6 a M = 1.1a. [M]0 = 0.2065 mol L-1. Molecular weight of isolated polymer PMP after quenching with H+ (Mn = 7900, PDI = 1.12)    103  Table B.2. Monomer conversion data collected for the polymerization of 1.1a using 4% BnLi as initiator in toluene and TMEDA solvent system at T = 328.2K. Entry Percent conversion determined by 31P NMR [M]a  mol L-1 In[M]0/[M] Time (h) 1 0.0666 0.192756 0.068872864 0.25 2 0.4444 0.114729 0.587731108 0.75 3 0.7084 0.060206 1.232531106 1.25 4 0.8000 0.0413 1.609437912 1.75 5 0.8889 0.022944 2.197224577 2.25 6 0.9349 0.013436 2.732326467 2.75 7 0.9596 0.008341 3.209128473 3.25 8 0.9828 0.003551 4.062977726 3.75 a M = 1.1a. [M]0 = 0.2065 mol L-1. Molecular weight of isolated polymer PMP after quenching with H+ (Mn = 7800, PDI = 1.07)              104  Table B.3. Monomer conversion data collected for the polymerization of 1.1a using 4% BnLi as initiator in toluene and TMEDA solvent system at T = 333.2K. Entry Percent conversion determined by 31P NMR [M]a  mol L-1 In[M]0/[M] Time (h) 1 0.1878 0.167723 0.207989304 0.25 2 0.3520 0.133804 0.433922981 0.5 3 0.5016 0.102916 0.696391911 0.75 4 0.6268 0.077067 0.98563021 1 5 0.7086 0.060176 1.233026625 1.25 6 0.7911 0.043133 1.566008355 1.5 7 0.8153 0.038146 1.688877361 1.75 8 0.8886 0.023001 2.194743725 2 9 0.9047 0.019674 2.350984705 2.25 10 0.9397 0.012443 2.809179779 2.5 a M = 1.1a. [M]0 = 0.2065 mol L-1. Molecular weight of isolated polymer PMP after quenching with H+ (Mn = 7900, PDI = 1.05).        105  Table B.4. Monomer conversion data collected for the polymerization of 1.1a using 4% BnLi as initiator in toluene and TMEDA solvent system at T = 338.2K. Entry Percent conversion determined by 31P NMR [M]a  mol L-1 In[M]0/[M] Time (h) 1 0.1769 0.169973 0.194661769 0.25 2 0.4085 0.122139 0.525142644 0.5 3 0.5943 0.083769 0.902232375 0.75 4 0.6995 0.062059 1.202221271 1 5 0.7313 0.055481 1.314261158 1.25 6 0.7538 0.050842 1.401576985 1.5 7 0.7596 0.049636 1.425587187 1.75 8 0.8108 0.039077 1.664778007 2 a M = 1.1a. [M0 = 0.2065 mol L-1. Molecular weight of isolated polymer PMP after quenching with H+ (Mn = 7900, PDI = 1.10)             106  Table B.5. Monomer conversion data collected for the polymerization of 1.1a using 4% BnLi as initiator in toluene and TMEDA solvent system at T = 343.2K. Entry Percent conversion determined by 31P NMR [M]a  mol L-1 In[M]0/[M] Time (h) 1 0.2109 0.162958 0.236809742 0.25 2 0.5510 0.092713 0.80079009 0.5 3 0.7223 0.05734 1.281294891 0.75 4 0.8110 0.039018 1.666271829 1 5 0.8631 0.02826 1.988846478 1.25 6 0.8964 0.021403 2.266761005 1.5 7 0.9174 0.017062 2.493445093 1.75 8 0.9322 0.013997 2.69145323 2 9 0.9362 0.013181 2.751518292 2.25 a M = 1.1a. [M]0 = 0.2065 mol L-1. Molecular weight of isolated polymer PMP after quenching with H+ (Mn = 7800, PDI = 1.07)         107  Table B.6. Monomer conversion data collected for the polymerization of 1.1a using 4% BnLi as initiator in toluene and TMEDA solvent system at T = 348.2K. Entry Percent conversion determined by 31P NMR [M]a  mol L-1 In[M]0/[M] Time (h) 1 0.3533 0.133545 0.43586498 0.25 2 0.5978 0.083045 0.910916316 0.5 3 0.7146 0.058936 1.253848094 0.75 4 0.7810 0.04523 1.51854994 1 5 0.8347 0.034131 1.800091329 1.25 6 0.8613 0.028644 1.975371859 1.5 7 0.8826 0.024234 2.14254544 1.75 a M = 1.1a. [M]0 = 0.2065 mol L-1. Molecular weight of isolated polymer PMP after quenching with H+ (Mn = 7900, PDI = 1.09)   

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