One-Pot Synthesis of CO ₂ -Based Polycarbonate Macrodiols: (Propylene Carbonate)/(Ethylene Carbonate) Composition Evolution Versus Physicochemical Performance

Over the past decade, CO2-based macrodiols have attracted significant attention as green and sustainable materials. This study presents a metal-free, one-pot terpolymerization of CO2, propylene oxide (PO), and ethylene oxide (EO). The reaction was catalyzed by a triethylborane/tetrabutylammonium chloride (TEB/TBACl) Lewis pair system, employing 1,4-butanediol (BDO) as the chain transfer agent (CTA). A series of well-defined poly(ethylene-co-propylene carbonate) macrodiols (PEPCDLs) with tunable (propylene carbonate)/(ethylene carbonate) compositions were synthesized, alongside the poly(propylene carbonate) diol (PPCDL) and poly(ethylene carbonate) diol (PECDL) prepared from PO/CO2 and EO/CO2, respectively. Comprehensive structural analyses were conducted, and the reaction mechanism was systematically investigated. Based on this, a pathway for the chain transfer process is proposed. The influence of PPC/PEC composition evolution on macrodiols’ thermal properties, viscosity, and primary hydroxyl group content was thoroughly evaluated. Furthermore, a series of thermoplastic polyurethanes (TPUs) were prepared from these CO2-based macrodiols. Experimental results demonstrate that their thermal and mechanical properties can be precisely tailored by adjusting the PPC/PEC content. The PEPCDL-based TPUs effectively combine the high tensile strength of PPCDL-TPU and the high toughness of PECDL-TPU. Specifically, the PEPCDL-4/4-TPU exhibits a tensile strength of 32.4 MPa and an elongation at break of 625%. This study presents a sustainable strategy for converting CO2 into value-added polyurethane materials, offering a viable alternative to conventional polyester/polyether polyols.