Copolymerization of PO/CO2 and Lactide by a Dinuclear Salen-Cr(III) Complex: Gradient and Random Copolymers with Modificable Microstructure

Copolymerization of propylene oxide (PO)/carbon dioxide (CO2) and lactide (LA) is achievable to form new copolymers, combining the advantages of both poly(propylene carbonate) (PPC) and polylactide (PLA). In this study, we designed a dinuclear Salen-Cr(III) complex, which showed higher efficiency for copolymerization of PO/CO2 and LA than that of mononuclear Salen-Cr(III) complex. Besides, we successfully obtained gradient and random copolymers of PPC-PLA in one pot. Furthermore, by adjusting reaction temperature, block ratios of PPC/PLA in copolymers were controllable (block ratio of PPC/PLA=1.0 at 40 °C, while block ratio of PPC/PLA=0.5 at room temperature). While increasing the reaction temperature to 60 °C, conversion of LA was much faster than that of PO so that gradient copolymers were obtained.