One-Step and Metal-Free Synthesis of Triblock Quaterpolymers by Concurrent and Switchable Polymerization

A one-step and metal-free route to triblock quaterpolymers from mixtures of vinyl monomers, epoxides, anhydrides, and racemic lactide (rac-LA) has been described, which bridges three polymerization cycles involving ring-opening copolymerization (ROCOP) of epoxides/anhydrides, ring-opening polymerization (ROP) of rac-LA, and RAFT polymerization of vinyl monomers. Taking advantage of the switchable polymerization between ROCOP and ROP, concurrent chain propagation of ROCOP/RAFT and ROP/RAFT sequentially occurs by using a trithiocarbonate compound with carboxylic group (TTC-COOH) as a versatile chain transfer agent. The multiple-chain transfer effect enables independent and precise control over the molecular weights of the three blocks and ensures narrow distribution of the resultant triblock quaterpolymers (D < 1.20). This work demonstrates the possibility to acquire block copolymers with high degree of structural complexities in a single efficient process by combining different block polymerization strategies.