Construction of ring-based architectures via ring-expansion cationic polymerization and post-polymerization modification: design of cyclic initiators from divinyl ether and dicarboxylic acid†
Topologically unique polymers made of a cyclic chain such as tadpole and figure-eight polymers were synthesized via ring-expansion cationic polymerization (RECP) of vinyl ether with a functionalized cyclic initiator, followed by post-polymerization modification (PPM) reactions. Cyclization reactions between 2,2-dimethyl-1,3-divinyloxy propane and a substituted phthalic acid (PA) efficiently afforded cyclic compounds where two hemiacetal ester (HAE) bonds for the initiating sites of RECP and the substituent for PPM were embedded in one ring. The cyclic compounds worked as initiators for RECP to give cyclic polymers. A bromine-substituted PA was used in the cyclization for the synthesis of pinpoint functionalized cyclic polymers via Suzuki–Miyaura cross coupling (SMC) as the PPM reaction, and the functional group was further utilized for the construction of tadpole and figure-eight polymers. The resultant figure-eight polymer showed lower intrinsic viscosity than linear and cyclic polymers.