Controlled synthesis of vinyl-functionalized homopolymers and block copolymers by RAFT polymerization of vinyl methacrylate

Reversible addition-fragmentation chain transfer (RAFT) polymerization of an asymmetrical divinyl monomer, vinyl methacrylate (VMA), was investigated under various conditions. RAFT polymerization of VMA using a dithioester-type chain transfer agent (CTA) under suitable conditions afforded soluble polymers with a high content of pendant vinyl ester side chains in sufficient yields (>70%). The monomer concentration, the nature of the CTA, and the CTA/initiator ratio were found to affect the polymerization reaction and the structure of the resulting polymers; this behavior is attributed to the relative propensities for intermolecular propagating/cross-linking reactions and intramolecular cyclization. A kinetic study of the RAFT polymerization of VMA with the dithioester-type CTA 1 suggested that the propagation reaction of the methacryloyl group proceeded predominantly with a certain level of intramolecular cyclization during the early stage of the polymerization and intermolecular cross-linking during the final stage of the polymerization. Block copolymers with one segment featuring pendant vinyl functionality were synthesized by RAFT polymerization of VMA using poly(methyl methacrylate) as a macro-chain transfer agent (macro-CTA).