Topological Star-Shaped and Mechanical Performance Enhanced Poly(propylene carbonate) Derived from CO ₂ : One-Pot Controllable Synthesis, Catalytic Mechanism, and Structure–Property Relationship Study

Poly(propylene carbonate) (PPC) with star-shaped topology is an emerging, promising class of PPC with potential applications in various areas, such as thermoplastics, adhesives, etc. To facilitate its large-scale industrial implementation, it is challenging yet imperative to fabricate star-shaped topological PPC materials with sufficient mechanical properties and well-defined structures via highly efficient and well-controlled polymerization and meanwhile, to elucidate in depth the polymerization mechanism and structure–property relationship. In this work, a nonmetallic tetrabutylammonium salt of benzene tetracarboxylic acid/triethyl borane (TBTA/TEB) multiend initiator catalytic system was employed to achieve efficient and controllable one-pot synthesis of high-molecular-weight, highly entangled CO2-based PPC with topological star shape. 1H NMR spectroscopy was demonstrated to be a useful method to confirm the multiend initiation behavior during polymerization. Density functional theory (DFT) calculations elucidated the alternating insertion pathway of PO and CO2 in the copolymerization. Electrostatic potential (ESP) analysis disclosed the multiend initiator catalytic system’s synergistic mechanism of simultaneous rapid initiation, efficient monomer activation, and stabilization of active species. Systematic characterizations reveal that topological star-shaped PPC exhibits markedly improved tensile strength, elongation at break,and toughness compared with linear PPC, which is closely related to the significantly enhanced polymer chain entanglement due to the topological star-shaped architecture. This study not only provides theoretical insights into the rational design of CO2-based polymers, but also offers a promising strategy for the development of sustainable, high-performance polymer materials with broad application potential.