Thermodynamically driven closed-loop recyclable bridged polymers: from molecular design to high-performance materials

The escalating plastic pollution crisis and the limitations of conventional mechanical and open-loop recycling strategies underscore the urgent need for high-performance polymers with intrinsic chemical recyclability. Bridged polymers, characterized by the incorporation of non-aromatic cyclic units sharing three or more atoms with the main chain, have recently emerged as a powerful design paradigm to reconcile the long-standing trade-off between performance and closed-loop recyclability. By embedding rigid bridged structures into the polymer backbone, these materials exhibit distinct advantages, including tunable thermodynamics of polymerization–depolymerization equilibria, enhanced chain packing, and superior thermal and mechanical properties compared with traditional aliphatic polymers. This review systematically summarizes recent advances in bridged polyesters, polyamides, and polythioesters, highlighting monomer design principles, catalytic strategies, polymerization mechanisms, and depolymerization pathways. Special emphasis is placed on the hybrid monomer strategy, where high ceiling-temperature (HCT) and low ceiling-temperature (LCT) motifs are fused into a single bridged structure to simultaneously achieve high-performance usage stability and efficient chemical recycling. In addition, emerging developments in orthogonal polymerizations and multifunctional bridged monomers enable the construction of diverse materials from a single monomer platform, further broadening application potential. Finally, the opportunities and challenges in this field are discussed, including catalyst generality, mild depolymerization conditions, and the scalable synthesis of new bridged monomers. Collectively, bridged polymers represent a transformative class of intrinsically circular polymers, offering new pathways toward sustainable, high-performance materials for next-generation applications in packaging, engineering plastics, and energy-related devices.