Kinetics of RAFT copolymerization of vinyl ether and maleic anhydride monomers

Alternating copolymerization has attracted significant interest for applications where monomers are arranged in a nearly perfect sequential pattern. This study analyzed the Reversible Addition-Fragmentation Chain Transfer (RAFT) copolymerization of butyl vinyl ether (BVE) and maleic anhydride (MAn) at various initial monomer feed compositions. The effects of feed ratio and chain length on copolymer composition, molecular weight distribution, and monomer incorporation were investigated. Kinetic studies revealed that while the system approaches nearly alternating behavior, BVE exhibited slightly faster incorporation than MAn under equimolar conditions. In non-equimolar feeds, the relatively less abundant monomer was preferentially incorporated. To interpret these observations, both the terminal model and a complex participation model were employed. While the terminal model predicted near-ideal alternating copolymerization, the complex participation model captured the contribution of a charge transfer (CT) complex between BVE and MAn. The results indicated that complex-mediated propagation dominated at low conversion, whereas direct monomer addition became more significant at higher conversion due to decreasing monomer and complex concentrations. These findings provide a quantitative framework for understanding the interplay between CT complex formation and radical propagation in RAFT copolymerization.