High‐Molecular‐Weight Biodegradable CO₂/Propylene Oxide/Epichlorohydrin Terpolymers with Outstanding Gas Barrier Performance Synthesized Using an Organoboron Catalyst

As the sole commercial polycarbonate derived from CO₂, poly(propylene carbonate) (PPC) is still hindered by poor thermal stability and a low glass transition temperature. Herein, first, the terpolymerization of CO₂, propylene oxide (PO), and epichlorohydrin (ECH) to synthesize PPC-ECH terpolymers via one-pot and metal-free method using multinuclear organoboron catalysts is reported. The PPC-ECH terpolymers with well-rounded properties can be easily synthesized by adjusting reaction conditions, monomer ratios, catalyst types, and loading. The molecular weight of the PPC-ECH terpolymer can reach up to 59.4 kg mol^-1, which is the highest known. Notably, the synthesized PPC-ECH exhibits outstanding barrier performance with oxygen permeability as low as 1.31 cm³ mm (m² day)^-1 and water vapor permeability as low as 0.016 g mm (m² day)^-1, significantly lower than those of pure PPC or other common packaging materials. Importantly, the introduction of a small amount of ECH not only preserves the biodegradability of polycarbonate but also markedly enhances its mechanical properties, glass transition temperature, thermal stability, and flame retardancy, offering promising prospects for application in packaging materials.