学位論文 A Benign Initiating System for Cationic Polymerization of Vinyl Ethers and Styrene Derivatives : Silver Salt/ArylMethyl Halide/Lewis Base

林, 麗

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主指導教員 : 廣瀬卓司
AbstractAbbreviationsPublication ListChapter 1 Introduction ................................................................................................ 11.1 Cationic Polymerization.................................................................................... 11.1.1 Historical Background of Cationic Polymerization ................................ 11.1.2 Characteristics of Cationic Polymerization ............................................ 31.1.3 Monomers for Cationic Polymerization.................................................. 41.1.4 Conventional Catalysts for Cationic Polymerization .............................. 61.1.5 Industrial Cationic Polymerization ......................................................... 71.2 Living Cationic Polymerization of Vinyl Monomers ....................................... 81.2.1 Background of Living Cationic Polymerization ..................................... 81.2.2 Design of Living Cationic Polymerization ............................................. 91.2.3 Application of Living Cationic Polymerization .................................... 121.3 Aim of This Work ............................................................................................ 131.4 References ....................................................................................................... 14Chapter 2 Synthesis of Living Poly(vinyl ether)s and Block Copolymers by the Silver Salt / Aryl Methyl Halide /Lewis Base Initiating System ............................ 172.1 Introduction ..................................................................................................... 172.2 Experimental ................................................................................................... 172.2.1 Materials ............................................................................................... 172.2.2 Polymerization ...................................................................................... 182.2.3 Characterization .................................................................................... 182.3 Results and Discussion ................................................................................... 192.3.1 Cationic Polymerization Initiated by AgClO4/BnBr System ................ 192.3.2 Effects of Solvent, Added Base, and Temperature on AgClO4/BnX Initiating System ............................................................................................ 222.3.3 Cationic Polymerization by AgClO4/Ph2CHBr Initiating System ........ 252.3.4 Cationic Polymerization by Various Silver Salt/Aryl Methyl Halide Initiating Systems........................................................................................... 312.3.5 Polymerization Mechanism with AgClO4/Aryl Methyl Halide Initiating System ............................................................................................................ 322.3.6 Effects of Alkyl Sulfide on the Cationic Polymerization Behavior of VEs ................................................................................................................. 342.3.7 Copolymerization of VEs by AgClO4/Ph2CHBr Initiating System ...... 402.4 Conclusions ..................................................................................................... 422.5 References ....................................................................................................... 43Chapter 3 Cationic Polymerization of Styrene Derivatives by the Silver Salt/Aryl Methyl Halide /Lewis Base Initiating System .......................................................... 463.1 Introduction ..................................................................................................... 463.2 Experimental ................................................................................................... 463.2.1 Materials ............................................................................................... 463.2.2 Polymerization ...................................................................................... 463.3 Results and Discussion ................................................................................... 473.3.1 Cationic polymerization of Poly(St)s Initiated by AgClO4 (AgOTf) /Ph2CHBr ....................................................................................................... 473.3.2 Added Base Influence on Cationic polymerization Behavior of Poly(pMOS) ................................................................................................... 513.3.3 Initiator Influence on Cationic polymerization Behavior of Poly(pMOS)........................................................................................................................ 543.4 Conclusions ..................................................................................................... 563.5 References ....................................................................................................... 57Chapter 4 Conclusion and Outlook .......................................................................... 58Acknowledgements .................................................................................................... 60
A combination of aryl methyl halides and silver salts was studied as an environmentally benign initiating system for cationic polymerization of vinyl ethers (VEs) and styrene derivatives (Sts). The reaction of aryl methyl halide and silver salt readily generates a benzyl cation, which induces the cationic polymerization. The reactivity of the benzyl cations and growing carbocations could be effectively controlled by sulfides, especially dimethyl sulfide (Me2S), which exerts a strong effect as an additive on the rate of polymerization, resulting in a narrower MWD range than the system without it. Diethyl ether was important as reaction solvent in the initiation step.Various EVs, isobutyl vinyl ether (IBVE), ethyl vinyl ether (EVE) and isopropyl vinyl ether (IPVE), were employed for cationic polymerization. The living nature of poly(IBVE) synthesized using the AgClO4/Ph2CHBr/Me2S system was examined by a successful chain extension experiment. Detailed study of the effects of Me2S, various benzyl cations and the addition order of the reagents revealed that the reaction was controlled by the electronic and steric features of aryl methyl halides, LBs, and IBVE, and a plausible reaction mechanism was presented. Differences in the modes of coordination of added bases to benzyl cations were clearly demonstrated by 1H NMR.Cationic polymerizations of EVE and IPVE, also proceeded in a controlled fashion using AgClO4/Ph2CHBr/Me2S system. The effects of tetrohydrothiophene (THT) and diethyl sulfide (Et2S) were further investigated. Choosing a sulfide with suitable nucleophilicity was important for achievement of controlled polymerization. In addition, depending on monomer reactivity, selecting the reaction temperature was also essential for suppressing side reactions. The copolymerization of IBVE and EVE by the AgClO4/Ph2CHBr system with Me2S proceeded smoothly in CH2Cl2 at −23 °C.For polymerization of Sts, it was found that the polymerization of less reactive monomers (styrene, p-methoxymethylstyrene and p-butoxymethylstyrene) proceeded in an uncontrolled fashion, even in the presence of added base or ammonium salt. The polymerization of highly reactive p-methoxystyrene (pMOS) was effectively controlled by using sulfides (Me2S, Et2S and THT), which were shown to be effective Lewis bases. This polymerization behavior was dramatically influenced by the electronic and steric features of aryl methyl halides and LBs and the difference of modes of coordination between benzyl cations and the added bases were also demonstrated by 1H NMR.
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