Exclusive One-Way Cycle Sequence Control in Cationic Terpolymerization of General-Purpose Monomers via Concurrent Vinyl-Addition, Ring-Opening, and Carbonyl-Addition Mechanisms

Cationic terpolymerization of vinyl ether (YE), oxirane, and ketone successfully proceeded via unprecedented concurrent vinyl-addition, ring-opening, and carbonyl-addition mechanisms. In particular, the use of cyclohexene oxide as an oxirane resulted in terpolymerization via an exclusive one-way cycle, i.e., the reactions occurred only in the VE -> oxirane, oxirane -> ketone, and ketone -> VE directions. Terpolymers that have repeating units of (VE similar to 2-oxirane(similar to 2)-ketone)(n) were obtained under appropriate conditions. In addition, no two-monomer combination achieved efficient copolymerization, which suggests that three specific types of crossover reactions are required for successful terpolymerization. The presence of a ketone, a compound that has rarely been employed as a monomer, is indispensable for a one-way cycle: terpolymerization also proceeded with an aliphatic aldehyde but resulted in two-way crossover reactions at the aldehyde-derived propagating ends.