Cationic Polymerizability of Vinyl Acetate: Alternating Copolymerization with 1,3-Dioxolan-4-ones and Branched Copolymer Formation with Cyclic Acetals

Abstract

Azuma J., Kanazawa A., Aoshima S.. Cationic Polymerizability of Vinyl Acetate: Alternating Copolymerization with 1,3-Dioxolan-4-ones and Branched Copolymer Formation with Cyclic Acetals. Macromolecules 55, 6110 (2022); https://doi.org/10.1021/acs.macromol.2c00979.Vinyl acetate (VAc) potentially exhibits cationic polymerizability due to electron donation from the oxygen atom adjacent to the vinyl group through resonance. In this study, cationic copolymerizations of VAc and comonomers with little or no homopolymerizability were shown to proceed with very frequent crossover reactions. Alternating copolymers were produced when 1,3-dioxolan-4-ones, which generate a carbocation adjacent to oxygen via ring opening and exhibit no homopolymerizability, were used as comonomers in copolymerizations with VAc catalyzed by GaCl3. An alternating copolymer with an Mnof 6.4 × 103was obtained in the copolymerization of VAc and 2,5-dimethyl-1,3-dioxolan-4-one. Moreover, branched copolymers containing a portion with molecular weights over 105were generated in copolymerizations of VAc with cyclic acetals exhibiting appropriate structures. Specifically, abstraction of the VAc-derived acetoxy group from the hemiacetal ester moiety in the main chain most likely resulted in carbocation generation and subsequent reaction with a monomer to form branched structures. The reaction of a hemiacetal ester moiety did not occur likely due to the rigid cyclic structure when α-angelicalactone was used instead of VAc, resulting in an alternating copolymer with an Mnof 10.4 × 103in the copolymerization with 1,3-dioxane. The copolymerization mechanisms generating such copolymer structures were discussed based on detailed analyses of the polymerization products by NMR spectroscopy