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5-Substituted Triazolinyls As Novel Counter Radicals in Controlled Radical Polymerization

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5-Substituted Triazolinyls As Novel Counter Radicals in Controlled Radical Polymerization 5-Substituted Triazolinyls as Novel Counter Radicals in Controlled Radical Polymerization Thesis for completion of the degree “Doktor der Naturwissenschaften” in the Department of Chemistry and Pharmaceutics of Johannes Gutenberg University, Mainz by Maxim Peretolchin Mainz 2004 The work completed between October 1999 and November 2002 at the Max- Planck-Institute for Polymer Research, Mainz, Germany under the supervision of Prof. Dr. K. Müllen. 4 Content 1 State of the art 9 1.1 Polymer Chemistry 9 1.1.1 Introduction 9 1.1.2 Characterization of polymers 11 1.2 Coordination polymerization 12 1.3 Ionic polymerization 12 1.4 Free radical polymerization 15 1.4.1 Principles of radical polymerization 15 1.4.2 Kinetics of free radical polymerization 19 1.4.3 Comparison of free radical and ionic (living) polymerization 21 1.5 Controlled (living) radical polymerization 23 1.5.1 Overview 23 1.5.2 Atom transfer radical polymerization (ATRP) 24 1.5.3 Reversible addition fragmentation chain transfer (RAFT) 26 1.6 Stable free radical polymerization (SFRP) 27 1.6.1 Nitroxide mediated radical polymerization (NMRP) 28 1.6.2 Controlled radical polymerization mediated by stable radicals other than 32 nitroxides 1.6.3 Carbon-centered radicals 33 1.6.4 Nitrogen-centered radicals 34 1.7 Triazolinyl radicals 34 1.7.1 Syntheses and properties 34 1.7.2 Triazolinyl mediated controlled radical polymerization 38 1.8 Comparison of ATRP, SFRP, and RAFT 39 1.9 Kinetics of SFRP 39 1.9.1 Self-regulation concept 43 1.10 Materials, academic, and industrial prospects 45 2 Goals of the current work 47 3 Results & discussion 51 3.1 Planning of syntheses of new triazolinyl derivatives 51 3.2 Development of synthetic route to benzhydrylamine derivatives 54 3.2.1 Previously used methods 54 5 3.2.2 Synthetic route via oximes 55 3.3 Syntheses of benzhydrylamine derivatives 56 3.3.1 Synthesis of 4,4`-(perfluoro-n-hexyl)benzophenone (73) and 4,4´-{2-[2- 56 (2-methoxy-ethoxy)-ethoxy]-ethoxy}benzophenone (70) 3.3.2 Syntheses of benzophenone oxime derivatives 57 3.3.3 Syntheses of benzhydrylamine derivatives from oximes 59 3.3.4 Syntheses of benzhydrylamine derivatives functinalized by groups 61 sensitive to reduction 3.3.5 Syntheses of triazolins (cyclization step) 62 3.3.6 Syntheses of triazolinyls (oxidation step) 64 3.4 Properties of the synthesized triazolinyl radicals 66 3.4.1 Optical spectroscopy 66 3.4.2 ESR & stability 68 3.4.3 Other properties 86 3.5 Polymerization experiments in the presence of triazolinyl radicals 86 3.5.1 Polymerizations of styrene in the presence of triazolinyl radicals 87 3.5.2 Discussion of the styrene polymerization experiments 104 3.5.3 Polymerizations of methylmethacrylate (MMA) in the presence of 109 triazolinyl radicals 3.5.4 Discussion of MMA polymerization experiments 121 3.6 Polymerization of other monomers (non styrene and MMA) in the presence 126 of triazolinyl radicals 3.6.1 Polymerization of ethylmethacrylate (EMA) in the presence of 1,3– 126 diphenyl-5,5-di(4-chlorophenyl)-∆3-1,2,4-triazolin-2-yl (77) 3.6.2 Polymerizations of 2,2,2-trifluoroethylmethacrylate (FEMA) in the 128 presence of triazolinyl radicals 77 and 86 3.6.3 Polymerization of n-butylmethacrylate (n-BMA) in the presence of 1,3– 132 diphenyl-5,5-di(4-chlorophenyl)-∆3-1,2,4-triazolin-2-yl (77) 3.6.4 Polymerization of 4-vinylpyridine (4-VP) in the presence of 1,3- 135 diphenyl-5,5-bis-4-dimethylaminophenyl-∆3-1,2,4-triazolin-2-yl (82) 3.6.5 Summary of the application of the triazolinyl radicals 77 and 82 for the 137 controlled radical polymerization of the methacrylates and 4-VP 6 3.7 Syntheses of block copolymers 138 3.7.1 Synthesis of block copolymers starting from polystyrene (PS) 140 macroinitiator 3.7.2 Synthesis of block copolymers initiated from polymethylmethacrylate 145 (PMMA) macroinitiator 4 Conclusions and outlook 154 5 Experimental part: syntheses 161 5.1 Synthesis of N-phenylbenzenecarbohydrazonoyl chloride 161 5.2 Synthesis of 1,3,5,5-tetraphenyl-∆3-1,2,4-triazolin-2-yl 164 5.3 Synthesis of 1,3–diphenyl-5,5-di(4-methoxyphenyl)-∆3-1,2,4-triazolin-2-yl 167 5.4 Synthesis of 1,3–diphenyl-5,5-di(4-chlorophenyl)-∆3-1,2,4-triazolin-2-yl 172 5.5 Synthesis of 1,3-diphenyl-5,5-bis(4-dimethylaminophenyl)-∆3-1,2,4- 177 triazolin-2-yl 5.6 Synthesis of 1,3-diphenyl-5,5-di(4-biphenyl)-∆3-1,2,4-triazolin-2-yl 182 5.7 Synthesis of 1,3–diphenyl-5,5-di(4-fluorophenyl)-∆3-1,2,4-triazolin-2-yl 186 5.8 Syntheses of 1,3–diphenyl-5,5-di(4-bromophenyl)-∆3-1,2,4-triazolin-2-yl 191 and 1,3,5–triphenyl-5-(4-bromophenyl)-∆3-1,2,4-triazolin-2-yl 5.9 Synthesis of 1,3-diphenyl-5,5-di(nitrophenyl)-∆3-1,2,4-triazolin-2-yl 197 (mixture of isomers) 5.10 Synthesis of 1,3-diphenyl-5,5-di(3-trifluoromethylphenyl)-∆2-1,2,4- 202 triazolin-2-yl 5.11 Synthesis of 1,3-diphenyl-5,5-di(4-(perfluoro-n-hexyl)phenyl)-∆3-1,2,4- 207 triazolin-2-yl 5.12 Synthesis of 1,3-diphenyl-5,5-di(2-thiophenyl)-∆3-1,2,4-triazolin-2-yl 214 5.13 Synthesis of 1,3-diphenyl-5,5-di(2-pyridyl)-∆2-1,2,4-triazolin 221 5.14 Synthesis of 1,3-diphenyl-5,5-di(4-acetophenyl)-∆2-1,2,4-triazolin 223 6 Experimental part: methods 227 6.1 Removal of moisture from a flask prior to water sensitive reactions 227 6.2 Soxhlet extraction 227 6.3 Melting point measurement 228 6.4 Elemental analysis 228 6.5 HCl gas generation 228 6.6 Purification of the chemicals 228 7 6.6.1 Dibenzoyl peroxide (BPO) (10) 228 6.6.2 Water 228 6.6.3 Monomers 228 6.6.4 2,2'-Azobis-iso-butyronitrile (AIBN) (9) 229 6.7 Gravimetrical determination of monomer conversion 230 6.8 GC determination of monomer conversion 230 6.9 Recognition of triazolin spots on TLC plates 232 6.10 Polymer syntheses 232 6.11 Block copolymer synthesis 232 6.12 “Freeze-thaw” technique 233 6.13 Determination of molecular weights of polymers 233 6.14 HPLC 233 6.15 Mass spectroscopy 233 6.16 NMR 234 6.17 ESR 234 6.18 UV-Vis spectroscopy 234 6.19 Polymerizations in supercritical CO2 234 7 Abbreviations & remarks 235 8 Acknowledgements 237 9 Supplementary information 238 9.1 Incomplete syntheses 238 9.1.1 Synthesis of 1,3–diphenyl-5,5-di-(4{2-[2-(2-methoxy-ethoxy)-ethoxy]- 238 ethoxy}phenyl)-∆2-1,2,4-triazolin 9.1.2 Synthesis of 1´,3´,1´´,3´´-tetraphenyl-dispiro(9,10-dihydroantracene- 241 [9.5´,10.5´´]-di-(∆2-1,2,4-triazolin) 9.2 Polymerization in supercritical CO2 243 9.3 Datasheets for polymerization experiments 244 10 Biography 250 8 1. State of the art 1.1. Polymer chemistry 1.1.1. Introduction Between 1913 and 1915, several reports on the self-condensation of butadiene came from the group of Lebedev.1,2,3 The products obtained were thought to be cyclic dimers of butadiene, but Lebedev also proposed the possible existence of long chains consisting of butadiene units. In 1920, Staudinger published a paper,4 in which the polystyrene structure formed by long linear chains of styrene blocks; similarly, the paraformaldehyde structure of repeating oxymethylene units was first proposed. This was one of the first ideas, which laid the ground for the contemporary understanding of polymer structures. Molecules able to add to other molecules of the same kind to form condensation products with relatively high molecular weight and a repeating molecular structure are known as monomers. The wider scientific community did initially not accept these ideas.5 Due to incorrect propositions and erroneous experimental data, the essentially correct concept of Staudinger was disregarded. However, Staudinger continued the development of his hypothesis and, in 1929, offered the new idea of the existence of two types of polymer structures: linear polymers and networks.6 The structure of the polymer strongly influences the properties of the polymer such as solubility, resistance to mechanical shock, and others. After 24 years, the works of Staudinger obtained recognition with the award of Nobel Prize for Chemistry in 1953.7 Subsequently, work by Carothers, Kuhn, Guth, Mark, and others completely changed generally accepted views in the field of the polymer science. Since that time, many new ideas have been brought into polymer science, but the initial concept that polymers are long chains consisting of many repeating (monomeric) units remains. New techniques have been developed to enable researchers to visualize and investigate even single molecules. Direct observations of macromolecules such as DNA8 or even smaller objects by these techniques directly confirm the existence of long polymer chains thus validating the initial concept of Staudinger. 1 S. V. Lebedev; B. K. Merezhkovskii, J. Russ. Phys. Chem. Soc., 45, 1249, 1913. 2 S. V. Lebedev, J. Russ. Phys. Chem. Soc., 45, 1296, 1913. 3 S. V. Lebedev, Chem. Abstracts, 9, 798, 1915. 4 H. Staudinger, Ber., 53, 1073, 1920. 5 P. J. Flory, Principles of polymer chemistry, Cornell University Press: Ithaca and London, 15th ed., 22 - 23, 1992. 6 H. Staudinger, Angewandte Chemie, 42, 67, 1929. 7 http://www.nobel.se/chemistry/laureates/1953/ 9 Until now, many reactions leading to polymer formation have been discovered.
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