Alternating-like Cationic Copolymerization of Styrene Derivatives and Benzaldehyde: Precise Synthesis of Selectively Degradable Copoly(styrenes)

Cationic copolymerizations of styrene derivatives and benzaldehyde (BzA) were systematically investigated for the purpose of both achieving living alternating copolymerization and creating "degradable polystyrene derivatives". As a result of the optimization of reaction conditions, the copolymerization of p-methylstyrene (pMeSt) and BzA was demonstrated to proceed in a living manner with GaCl3 as a catalyst in the presence of tetrahydropyran, yielding a copolymer with a nearly alternating sequence and a controllable molecular weight. sec-Benzylic ether structures were generated in the main chain of the copolymer due to the crossover reactions between the monomers; hence, the copolymer was degraded into low-molecular-weight compounds under acidic conditions. In addition, the copolymer exhibited a glass transition temperature and degradation temperature that were comparable to those of the pMeSt homopolymer.