Cationic Terpolymerization of Vinyl Ethers, Oxetane, and Ketones via Concurrent Vinyl-Addition, Ring-Opening, and Carbonyl-Addition Mechanisms: Multiblock Polymer Synthesis and Mechanistic Investigation

Abstract

Kanazawa A., Aoshima S.. Cationic Terpolymerization of Vinyl Ethers, Oxetane, and Ketones via Concurrent Vinyl-Addition, Ring-Opening, and Carbonyl-Addition Mechanisms: Multiblock Polymer Synthesis and Mechanistic Investigation. Macromolecules 50, 6595 (2017); https://doi.org/10.1021/acs.macromol.7b01250.Cationic terpolymerization of an alkyl vinyl ether (VE) with oxetane and methyl ethyl ketone (MEK) proceeded via concurrent vinyl-addition, ring-opening, and carbonyl-addition mechanisms. Highly selective crossover reactions occurred in a one-way cycle, resulting in the generation of multiblock polymers with constitutional repeating units comprising a poly(VE) block, a polyoxetane block, and a single MEK unit. The ketone efficiently functioned as a non-homopolymerizable monomer, which reacted with the oxetane-derived oxonium ion to generate an alkoxy group-adjacent carbocation or an oxocarbenium ion. Furthermore, the resulting carbocation allowed to react with only VEs. The polymerization, which was induced with an initiating system of Ph3C+PF6-, 2,6-di-tert-butylpyridine, and 1,4-dioxane, was partly mediated by long-lived propagating species. NMR analysis of the chain end structures revealed that mono- and difluorophosphate moieties generated via the hydrolysis of PF6- were partially responsible for the generation of these long-lived species