Rapid Block Copolymer Synthesis by Microwave-Assisted RAFT Polymerization

A single-mode microwave reactor was employed for the synthesis of well-defined homo-polymers and block copolymers of acrylamido and acrylate monomers via reversible addition-fragmentation chain transfer (RAFT) polymerization. The rates of polymerization of N,N-dimethylacrylamide and N-isopropylacrylamide were significantly higher than those observed under conventional heating conditions, yet the resulting homopolymers retained thiocarbonylthio end group functionality, as evidenced by efficient extension during block copolymerizations. Moreover, the dramatically enhanced rates of polymerization observed under microwave conditions did not negatively affect molecular weight control during homopolymerization or block copolymerization. In all cases, low polydispersity indices were observed, and the agreement between theoretical and experimental molecular weights was excellent. Rate enhancement may ultimately be the result of thermal effects not easily duplicated under conventional heating conditions. The methods outlined herein permit the total synthesis of block copolymers in a dramatically shortened period of time.