Self-condensing vinyl polymerization of a switchable chain transfer monomer for facile synthesis of star-shaped block copolymers

Abstract

Reversible addition-fragmentation chain transfer–self-condensing vinyl polymerization (RAFT-SCVP) is a versatile methodology for synthesizing hyperbranched polymers with a large number of chain transfer termini. Also, this method easily provides star-shaped block copolymers by another sequence of RAFT polymerizations. The design of such block copolymers, however, is still limited because the structure of chain transfer groups needed to be selected in accordance with the activity of monomers. This paper proposes a new class of styrene-type monomer, namely (4-vinyl)benzyl-N-methyl-N-(4-pyridyl)dithiocarbamate (VPDC), as a universal chain transfer monomer for facile synthesis of star-shaped block copolymers. VPDC effectively works as a chain transfer monomer for RAFT-SCVP in protonated form, providing hyperbranched polystyrene (PVPDC). The RAFT polymerization of a more-activated monomer (MAM), in this case N-isopropylacrylamide, was demonstrated from the same RAFT agent, whereas that of a less-activated monomer (LAM), namely vinyl acetate, was also achieved after switching the activity of the termini by deprotonation of the chain transfer agent (CTA). All in all, we believe that the current findings will enable facile synthesis of more varied star-shaped block copolymers with flexible design.