One-pot chemoenzymatic cascade polymerization under kinetic resolution conditions

A novel concept for the metal-free synthesis of block copolymers combining enzymatic ring-opening polymerization and nitroxide-mediated living free-radical polymerization from a bifunctional initiator is presented. Block copolymers comprising a poly(styrene) and poly(caprolactone) block were obtained in two consecutive polymerization steps (macroinitiation) and in a one-pot cascade approach without intermediate transformation or work up step. By optimization of the reaction conditions a high selectivity of both transformations could be realized in the cascade polymerization, resulting in high block copolymer yields. The same concept was successfully applied to enzymatic resolution polymerization of racemic 4-methyl--caprolactone combined with the living free-radical polymerization of styrene yielding block copolymers with high enantiomeric excess in the 4-methyl--caprolactone block.