Recent advances in plastic upcycling enabled by dynamic covalent cross-linking strategies

Plastic pollution poses a severe threat to ecological security, and conventional mechanical, energy-based, and chemical recycling technologies struggle to achieve efficient and high-value circularity due to issues such as performance degradation and process limitations. Dynamic covalent cross-linking strategies, leveraging the reconfigurability of reversible bonds, offer an innovative pathway for plastic upcycling. This review systematically examines dynamic covalent cross-linking approaches and underlying mechanisms across various polymer systems—polyolefins (C–H functionalization, direct C–H insertion, oxidative functionalization), polyesters (end-group mediation, grafting-cross-linking, blend-based dynamic network construction, chain scission coupled with dynamic cross-linking), and mixed plastics (chain scission combined with dynamic cross-linking, in situ compatibility via highly reactive cross-linkers). Research demonstrates that rational design of dynamic linkages (e.g., esters, boronate esters, disulfide bonds) and cross-linked architectures can significantly enhance material properties, including mechanical strength, thermal stability (improved creep resistance and high-temperature dimensional integrity), and reprocessability, while enabling functional upgrades such as foaming, gas barrier enhancement, and self-healing. In mixed plastic systems, in situ dynamic cross-linking effectively addresses compatibility challenges, facilitating the synergistic valorization of multi-source plastic waste. Dynamic covalent cross-linking strikes a balance between structural stability and recyclability, showing broad applicability and compatibility with industrial processes such as reactive extrusion. However, challenges remain regarding high costs, complex synthetic routes, and scalability. Future efforts should focus on optimizing dynamic bond design and processing efficiency, integrating value-added functionalities, and expanding application domains.