Concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers and oxiranes

In this review, our recent results on the concurrent cationic vinyl-addition and ring-opening copolymerization of vinyl ethers (VEs) and oxiranes are summarized, with particular emphasis on the strategies required to generate crossover reactions between different types of monomers. Most importantly, carbocation generation via the ring-opening reaction of the oxirane-derived oxonium ion is indispensable for the crossover reaction from oxirane to VE. Specifically, oxiranes with substituents that contribute to stabilizing these carbocations are suitable for concurrent copolymerization. Moreover, weak Lewis bases have been found to affect the frequency of crossover reactions through the promotion of the ring-opening reaction. This article also summarizes concurrent cationic vinyl-addition, ring-opening and carbonyl-addition terpolymerization via the one-way cycle of crossover reactions, the copolymerization of an alkoxyoxirane with VEs through the alkoxy group transfer mechanism, and the long-lived species-mediated cationic polymerization of vinyl monomers and cyclic formals.