Terpolymerization reactions of epoxides, CO2, and the third monomers toward sustainable CO2-based polymers with controllable chemical and physical properties.

Carbon dioxide (CO₂) serves as a cheap, abundant, and renewable C1 building block for the synthesis of organic compounds and polymers. Selective and efficient CO₂ fixation processes are still challenging because of the kinetic and thermodynamic stability of CO₂. Among various CO₂ fixation processes, the ring-opening copolymerization (ROCOP) of epoxides and CO₂ gives aliphatic polycarbonates with high atom economy, although the chemical and physical properties of the resulting polycarbonates are not necessarily satisfactory. Introducing the third monomers into this ROCOP system provides new terpolymers, and the thermal, optical, mechanical or degradation properties can be added or tuned by incorporating new polymer backbones derived from the third monomers at the expense of the CO₂ content. Here we review the terpolymerization reactions of epoxides, CO₂, and the third monomers such as cyclic anhydrides, lactones, lactides, heteroallenes, and olefins. The development of catalysts and the control of the polymer structures are described together with the chemical and physical properties of the resulting polymers.