Advances in carbon dioxide and propylene oxide copolymerization to form poly(propylene carbonate) over heterogeneous catalysts

Chemical conversion of carbon dioxide (CO2) into value-added products is an attractive industrial process because it offers several economic and environmental advantages. This review presents advances and challenges in the CO2 and propylene oxide (PO) co-polymerization using heterogeneous catalysts to form poly (propylene carbonate) (PPC), an environmentally friendly polymer with several applications. In the co-polymerization process, CO2 is employed as a green carbon source, an alternative to the toxic phosgene which has numerous negative environmental impacts. However, this route of polycarbonate production, is hindered by the chemical inertness of CO2, and to overcome this, various catalysts have been developed. A number of heterogeneous catalysts including carboxylates, double metal cyanides and composites, have achieved varying success in activating CO2 in the production of polycarbonates. The effect of different reaction conditions including pressure, temperature and solvent has been explored. The limitations faced by various heterogeneous catalysts and im-provements made over the past decades have been highlighted. Mechanistic insights for the production of PPC from CO2 and PO have been presented and the differences in both the regioselectivity and stereochemistry of the resultant polymers discussed.