Copolymerization of carbon dioxide and propylene oxide by several metallosalen-based bifunctional catalysts

A series of new metallosalen-based bifunctional catalysts with Co(III), Cr(III), Fe(III), Mn(III), and Ni(III) were synthesized for the first time, and a detailed study on the mechanism of the copolymerization of CO2 and propylene oxide (PO) was performed. Meanwhile, the impact factors of the reaction conditions (metal cations, temperature, CO2 pressure, and reaction time) on catalytic activity and selectivity were investigated. The results indicated that, with the increase of temperature, both the catalyst efficiency and the molecular weight of the copolymer decrease for all the five complexes. The salen-Co(III) complex demonstrated higher activity under mild conditions: reaction temperature at 30 degrees C, copolymerization time of 24hr, and 2 MPa of CO2 pressure. The DSC curve indicated that the PPC by the salen-Co(III) complex has the highest T-g of 46.19 degrees C. DTGA curves demonstrated that there were two thermal degradation peaks: the first is for the ester bond, and the second is for the CC bond.