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Controlled Cationic Polymerization of Sulfide-Containing Vinyl Ethers
Takeshi Namikoshi,Yuhei Watanabe,Ayaka Kaneda,Kazuma Ishikawa,Shinji Watanabe,Miki Murata 한국고분자학회 2022 Macromolecular Research Vol.30 No.1
The living cationic polymerizations of sulfide-containing vinyl ethers, namely, alkyl-sulfide-containing 2-(ethylthio)ethyl vinyl ether (ESEVE) and arylsulfide- containing 2-(phenylthio)ethyl and 2-[4-(methylthio)phenoxy]ethyl vinyl ethers (PSEVE and MSPEVE, respectively), were examined using HCl/ZnCl2, 1-(isobutoxy)ethyl acetate (IBEA)/Et1.5AlCl1.5, and IBEA /Et1.5AlCl1.5/SnCl4 as initiators. The polymerization of ESEVE terminated at a 35% monomer conversion, and a high-molecular-weight polymer was not obtained; instead, the nucleophilicity of the sulfur moiety in ESEVE led to cyclization, forming five-membered ring sulfonium species. In contrast, the side reactions were suppressed when PSEVE was used, which has a less-nucleophilic sulfur moiety on its benzene ring, and polymerization proceeded to an 88% conversion, affording a high-molecular-weight polymer with a narrow molecular weight distribution (Mw= 12,500, Mw/Mn = 1.18). Furthermore, cyclic sulfonium was not produced during the polymerization of MSPEVE, in which the sulfur atom was farther from the generated carbocation; the polymerization proceeded quantitatively producing a high-molecular-weight polymer with a narrow molecular weight distribution, despite the short lifetime of the growing species. In particular, a high-molecular-weight polymer with the narrowest distribution (Mw= 13,500, Mw/Mn = 1.08) was obtained when SnCl4 was used as the Lewis acid.