Mildly Recyclable and Biodegradable Structurally Polyethylene-Like Polyester Enabled by Unlocking Ester Accessibility.

Polyethylene-like polyesters, which incorporate chemically cleavable ester linkages into long methylene sequences while retaining characteristic polyethylene-like chain packing and semicrystalline mechanical behavior, are promising alternatives to persistent polyethylene because they combine comparable mechanical performance with the potential for chemical recycling and biodegradation. However, the ordered crystalline structures required for mechanical performance often sequester ester bonds within crystalline domains, creating an accessibility barrier that hinders chemical recycling and biodegradation. Herein, we decouple this trade-off through a crystallization modulation strategy by incorporating sterically hindered asymmetric pyrrolidone units into the polyester backbone. This molecular engineering approach relocates cleavable ester bonds from crystalline to amorphous domains while preserving semi-crystalline reinforcement, confirmed by x-ray structural analysis. The polymers exhibit tunable mechanical robustness, with tensile strength exceeding 18.7 MPa and lap-shear adhesion up to 15.3 MPa. They undergo complete depolymerization to easily separable soluble oligomers via methanolysis under ambient pressure, even within mixed-plastic streams, enabling closed-loop recycling. Furthermore, the amorphous enrichment of polar units accelerates biodegradation, achieving a mineralization rate 2.3 times that of conventional analogues. This work demonstrates a viable molecular design pathway to reconcile mechanical robustness, mild chemical recyclability, and enhanced environmental degradability in polyethylene-like materials, offering a route to mitigate long-term plastic persistence.