Mechanically Triggered Chemical Recyclable Polyethylene-Like Materials.

Polyethylene (PE) materials are indispensable to modern infrastructure due to their exceptional thermal, mechanical, and chemical resilience. However, the same properties that make these materials durable also render them environmentally persistent and unrecyclable by conventional means, posing a critical sustainability challenge. Here, we report a mechanochemically triggered, chemically recyclable PE-like system that enables the closed-loop recycling of cross-linked polyethylene (XLPE). Through palladium-catalyzed coordination copolymerization of ethylene with the cyclobutene-fused ester (CBE) comonomer, polar PE-like materials with tunable properties are achieved. Upon optimal mechanical activation in the presence of a radical inhibitor, the CBE units undergo ring opening, installing ester linkages into the polymer backbone. Notably, the high crystallinity of copolymers with low CBE content enables ball-milling to achieve activation efficiency comparable to cryo-milling. Subsequent ethanolysis of ester linkages cleanly converts the initial copolymer into multifunctional oligomers, which can be repolymerized after hydrogenation via transesterification to yield a recyclable XLPE with properties comparable to a commercial analogue. This work demonstrates a robust platform for reconciling the durability and recyclability of polyethylene, offering a transformative route toward sustainable polyolefins.