# Mechanically Triggered Chemical Recyclable Polyethylene‐Like Materials

## TL;DR

Scientists created a recyclable polyethylene-like material that can be broken down and reused without losing its key properties, offering a sustainable solution to plastic waste.

## Contribution

A mechanochemically triggered, chemically recyclable polyethylene-like system is developed for closed-loop recycling of cross-linked polyethylene.

## Key findings

- CBE units in the polymer backbone can be activated via ball-milling to form ester linkages.
- Ethanolysis and hydrogenation of the ester linkages produce multifunctional oligomers that can be repolymerized into XLPE with commercial-grade properties.
- Ball-milling achieves comparable activation efficiency to cryo-milling for copolymers with low CBE content.

## Abstract

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.

Polyethylene‐like copolymers with benchmark properties are prepared by embedding latent cyclobutene mechanophores to overcome PE's end‐of‐life limits. The mechanophores are inert in service but are selectively opened by solvent‐free ball milling to yield well‐defined telechelic oligomers. After ethanolysis/hydrogenation, these oligomers are repolymerized to cross‐linked PE with commercial‐grade properties, enabling a practical closed‐loop circularity.