One-Pot Synthesis of Polycarbonate-b-Polyester Block Copolymers From CO2/Epoxide/ε-Caprolactone Catalyzed by Salen-Cobalt(III) Complex

Abstract

A Salen-Co(III)-Cl catalyzed copolymerization strategy is developed for the controlled synthesis of polycarbonate-b-polyester block copolymers through a one-pot process involving CO₂, 4-vinyl-1-cyclohexene-1,2-epoxy (VCHO), and ε-caprolactone (ε-CL). This procedure is extended to the copolymerization of CO₂, VCHO, and lactide. The catalytic system is designed and optimized with temperature and CO₂ acting as triggers to switch between CO₂/epoxide copolymerization and ε-CL homopolymerization. In addition, introducing water as the chain transfer agent reduced the polydispersity index (PDI) of the block copolymers. The copolymer composition can be controlled by adjusting the concentration ratio of epoxides and ε-CL, yielding copolymers with carbonate molar ratios ranging from 14% to 67%. The block copolymers exhibit enhanced thermal stability, and the glass transition temperature (T _g) can be controlled by adjusting the block composition.