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

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 CO 2 , 4-vinyl-1-cyclohexene-1,2-epoxy (VCHO), and ε-caprolactone (ε-CL). This procedure is extended to the copolymerization of CO 2 , VCHO, and lactide. The catalytic system is designed and optimized with temperature and CO 2 acting as triggers to switch between CO 2 /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. Graphical Polycarbonate- b -polyester was prepared via the Salen-Cobalt complex catalyzed copolymerization of CO 2 , epoxide, and ε-caprolactone in one pot. Copolymerization of CO 2 and epoxide and homopolymerization of ε-caprolactone were switched by the control of CO 2 and temperature. By introducing H 2 O as a chain transfer agent, polyester- b -polycarbonate- b -polyester with lower PDI could be obtained.