Copolymerization of CO2 and propylene oxide using ZnGA/DMC composite catalyst for high molecular weight poly(propylene carbonate)

• Novel ZnGA is achieved with small particle size and increased surface area.
• ZnGA/DMC composite catalyst system presents synergistic effects on CO2/PO copolymerization.
• ZnGA/DMC composite catalyst shows high catalytic efficiency and selectivity to polycarbonates.
• The synthesized copolymer PPC has fairly high molecular weight (Mw = 3.9 × 105 g/mol).

The high yield and high molecular weight poly(propylene carbonate) (PPC) was synthesized via copolymerization of propylene oxide (PO) and carbon dioxide (CO2) catalyzed over zinc glutarate/double metal cyanide (ZnGA/DMC) composite catalyst. A fine crystalline ZnGA component was prepared using the crosslinked restrain effect of nonionic surfactant. Combined with a small amount of DMC, the ZnGA/DMC (molar ratio = 10:1) composite catalyst system showed an excellent synergistic effect on CO2/PO copolymerization with higher activity, selectivity, and shorter reaction time than those of the traditional ZnGA catalyst. Under the optimized reaction conditions, the molecular weight of PPC was up to 3.8 × 105 g/mol at the highest yield of 508.0 gpolym/gcat, and the selectivity was over 97.7% towards polycarbonates rather than polyether linkages. The alternating copolymer PPC exhibited good thermostability, high glass transition temperature (42.0 °C) and high decomposition temperature (5% weight loss at 253.4 °C). A synergistic mechanism of ZnGA/DMC composite catalyst was speculated.

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