Synthesis of High-Molecular-Weight Maleic Anhydride-Based Polyesters with Enhanced Properties

The synthesis of high-molecular-weight (MW) polyesters from the copolymerization of maleic anhydride (MA) and epoxides remains a challenge. Herein, we describe the copolymerization of MA with propylene oxide (PO) using a heterogeneous zinc–cobalt(III) double-metal cyanide complex (Zn–Co(III)DMCC), which afforded polyesters with high number-average molecular weights (Mns) of up to 82.8 kDa (previous record: 17.0 kDa). Moreover, the polyesters with cis-maleate could be transformed into biodegradable poly(propylene fumarate)s with high Mns via cis–trans isomerization. The key strategy is using excess MA (e.g., MA/epoxide molar ratio: 2–1/1, previously less than 1) and toluene as the solvent. This approach can afford polyesters with an ester content of >99%, restrain the cross-linking reaction of the generated polymers, and promote the separation of products and excess MA. This method was successfully extended to several epoxides to produce a family of high-MW polyesters (Mns: up to 152.0 kDa). The resultant MA-derived polyesters exhibit initial decomposition temperatures of up to 311.5 °C and significantly improved stress and elongation at break of up to 25.3 MPa and 1573%, respectively. This work provides a facile and atom-economic process for synthesizing high-MW MA-derived polyesters and biodegradable polyesters with the potential for large-scale production, and the polyesters have the potential to be used as biomedical materials and disposable packing materials.