3-Alkoxyphthalides as Nonhomopolymerizable, Highly Reactive Comonomers for ABC Pseudo-Periodic Terpolymers and Degradable Polymers via Cationic Co- and Terpolymerizations with Oxiranes and/or Vinyl Ethers

Abstract

3-Alkoxyphthalides (ROPTs) are promising candidate monomers that react with a cationic species at the carbonyl group and subsequently undergo ring-opening to generate a carbocation adjacent to both aryl and alkoxy groups (oxocarbenium ion). In this study, cationic polymerizations of ROPTs bearing methoxy, isopropoxy, tert-butoxy, or phenoxy groups were investigated with a particular focus on the copolymerizations with oxiranes. Cationic homopolymerization of ROPTs did not occur under any of the examined conditions. In contrast, cationic copolymerizations of ROPT with oxiranes, such as 4-vinyl-1-cyclohexene-1,2-epoxide (VCHO), proceeded smoothly via very frequent crossover reactions. The copolymers could be degraded under acidic conditions due to the cleavage of the acetal moieties generated by the crossover reactions from ROPT to VCHO. Cationic copolymerizations of ROPT with most of the examined vinyl ethers (VEs) and styrene derivatives did not proceed, likely due to inefficient crossover reactions from the vinyl monomers to ROPT. However, cationic terpolymerizations of VE, oxirane, and ROPT successfully proceeded via highly selective crossover reactions, resulting in ABC-type pseudo-periodic terpolymers under optimized conditions.