Crystalline Polyesters from CO2 and 2-Butyne via α-Methylene-β-butyrolactone Intermediate

The selective transformation of carbon dioxide into useful chemicals has attracted much attention in recent decades due to the economic and environmental benefits arising from the utilization of renewable source. Nevertheless, the reactions on incorporating CO2 into polymeric materials are very limited. The copolymerization of CO2 and alkynes to synthesize degradable polyesters is a thermodynamically unfavorable process, since the propagation step involving CO2 is a major obstacle. Herein, we report a strategy to conquer the thermodynamic and kinetic barriers for the copolymerization of CO2 and 2-butyne via α-methylene-β-butyrolactone (MβBL) intermediate. Subsequent ring-opening polymerization of the lactone intermediate mediated by achiral Salen aluminum complexes afforded syndiotactic-enriched polyesters with controllable molecular weight and narrow polydispersity. Notably, the resultant syndiotactic-enriched poly(MβBL) is a typical semicrystalline material. The present method provides access to a new class of CO2-based crystalline polymeric materials.