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Bulletin of the Chemical Society of Japan
Vol. 84 (2011) No. 1 P 26-39



BCSJ Award Article

Ring-opening polymerization of 3-alkyl-3-alkoxymethyl- or 3-alkyl-3-siloxymethyloxetanes is catalyzed by a triruthenium cluster, [Ru33-(η235-C12H8)}(CO)7], in the presence of trialkylsilanes, providing a novel accessible method for functionalized polyoxetanes of Mn = 103–105. Oxetanes having alkoxy-, fluoroalkoxy-, triethyleneglycoloxy-, and trialkylsiloxy functions undergo polymerization and copolymerization. Consumption rates of two monomers in the copolymerization of 3-benzyloxymethyl- and 3-trimethylsiloxymethyl-3-alkyloxetanes are almost the same, indicating formation of random copolymers. The organosilyl group in the polymer and copolymers with siloxymethyl side chains is converted to CH2OH or CH2OCOR groups by hydrolysis or silyl/acyl exchange. These protocols give the way to access polymers or copolymers bearing OH and OCOR side chains. A ruthenium-catalyzed reaction of 3-ethyl-3-hydroxymethyloxetane with trialkylsilanes results in dehydrogenative silylation to give 3-ethyl-3-siloxymethyloxetane, which is followed by ring-opening polymerization. Combination of tandem dehydrogenative silylation/ring-opening polymerization/the silyl/acyl exchange realizes one-pot synthesis of polymers with CH2OCOR side chains from 3-ethyl-3-hydroxymethyloxetane. DSC analyses of the formed polymers provided Tg and Tm data, which are a good example showing that the polymer properties are controlled by appropriate selection of functional groups at the side chain.
Treatment of 3-alkyl-3-alkoxymethyloxetanes or 3-alkyl-3-siloxymethyloxetanes with trialkylsilanes in the presence of [Ru33-(η235-C12H8)}(CO)7] (1) led to ring-opening polymerization to afford functionalized polyoxetanes of Mn = 103–105. Chemical conversion of siloxy groups at the side chain afforded functionalized polyoxetanes. Fullsize Image

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