Dynamic Diels-Alder Chemistry Toward Degradable and Dual Closed-Loop Recyclable Polyolefins

Plastics are vital to modern society, yet the rapid expansion of global plastic production has created demand for recyclable polymers to address environmental pollution caused by the inherent limitations of mechanical recycling. Herein, a facile strategy was developed by leveraging dynamic Diels-Alder (DA) covalent chemistry to construct degradable and dual-recyclable polyolefins. These polymers can be readily synthesized from anthracene-containing cyclic monomers through well-controlled ring-opening metathesis polymerization (ROMP). The comonomer content and molecular weight of the resulting copolymers can be precisely tailored by adjusting the monomer feed ratio, enabling modulation of the polymers' mechanical and thermal properties. Reversible DA bonds within the polymer backbone enabled the copolymers to undergo phototriggered retro-DA degradation to generate anthracene-terminated oligomers with 20-fold lower molecular weights, which could be quantitatively redimerized to achieve closed-loop recycling. Furthermore, these cyclic monomers could be directly homopolymerized via ROMP to yield structurally uniform, high-molecular-weight homopolymers with great photodegradation and photo-recycling properties. By integrating reversible photochemical DA degradation and Ru-catalyzed olefin metathesis depolymerization, a dual-recycling platform was constructed to realize efficient closed-loop recycling of polymeric materials. This work provides a versatile strategy for the rational design and fabrication of high-performance, sustainable polymeric materials.