Dual catalysis for the copolymerisation of epoxides and lactones

A dual catalysis system was developed to synthesize hydrolyzable polyether–polyester copolymers from propylene oxide and cyclic esters such as γ-butyrolactone, δ-valerolactone, and e-caprolactone. A bimetallic chromium catalyst active for the enantioselective polymerisation of propylene oxide and an organocatalyst active for the ring-opening polymerisation of lactones were used in conjunction with an alcohol chain shuttling agent to create new copolymers. The monomer and alcohol ratios were varied to yield a wide range of copolymers with varying monomer ratios, molecular weights, and crystallinities.