Self-Crosslinking All-Hydrocarbon Polyethylene Thermosets through Intrinsic Benzocyclobutene Cycloaddition

Abstract

Despite polyethylene's (PE) inherent thermal stability, its mechanical performance deteriorates above 80 °C, leading to material failure in high-temperature applications or solvents. While commercial cross-linked polyethylene (XLPE) technologies—γ-irradiation and peroxide-mediated cross-linking—address these issues partially, they suffer from uncontrolled network architectures, incomplete gelation, and performance compromises due to the introduction of byproducts or additives. Here, we report a benzocyclobutene (BCB)-based cross-linking strategy that eliminates additives and byproducts while preserving PE’s non-polar integrity. A norbornene-derived BCB monomer was rationally designed and incorporated into polyethylene via two pathways including ring-opening metathesis polymerization and coordination-insertion copolymerization. Thermal activation triggered a quantitative BCB [4+4] cycloaddition, achieving complete gelation and forming robust eight-membered ring networks. Cross-linked materials exhibited exceptional thermal stability, structural stability at high temperature, and intrinsic hydrophobicity. This methodology overcomes conventional challenges—residual catalysts, toxic byproducts—enabling the development of upgrading XLPE for potential applications. By marrying molecular design with industrially viable thermal processing, this work establishes BCB chemistry as a platform for next-generation polyolefin thermosets.