Boronic Ester-Enabled Covalent Adaptable Networks in Hydrogenated Nitrile Butadiene Rubber for Reprocessable High-Performance Elastomers

High-performance elastomer materials play indispensable roles in the aerospace, automotive, and petrochemical industries. However, conventional vulcanization systems rely on irreversible covalent bonds, which limit reprocessability and hinder sustainable use. Herein, we report a covalent adaptable network constructed from hydrogenated nitrile butadiene rubber (HNBR) that integrates high strength, outstanding toughness, reprocessability, and excellent oil and thermal resistance. Reactive epoxy groups were introduced into the HNBR backbone via sequential epoxidation and hydrogenation of NBR, followed by ring-opening reactions with terminal thiols of boronic ester cross-linkers (BDB) to construct the cross-linked network. The incorporation of dynamic boronic ester bonds enables topological rearrangement of the cross-linked network under thermal stimulation, thereby endowing the networks with reprocessability. The obtained materials display remarkable mechanical properties, with a maximum tensile strength of 27.8 MPa, elongation at break of 880%, and toughness of 67.6 MJ m –3, while retaining ∼15 MPa tensile strength even after three reprocessing cycles. Mechanistic analysis reveals that the superior strength and toughness stem from a synergistic mechanism involving dynamic covalent cross-linking, strain-induced crystallization, and hydrogen-bond dissipation. Furthermore, with carbon black reinforcement, the BDB-cross-linked systems rival the mechanical performance of conventional permanently DCP-cross-linked systems, while offering reprocessability and improved oil resistance. This work provides a general strategy for designing next-generation, reprocessable high-performance rubber materials for demanding industrial applications.