Preparation of hydrogenated nitrile butadiene rubber with pendant vinyl groups and its post-functionalization via cross-metathesis

Abstract

Hydrogenated nitrile butadiene rubber (HNBR) is extensively applied in aerospace, automotive, petrochemical, and defense industries. However, its inherent trade-off between oil resistance and low-temperature resistance, along with insufficient low-temperature behavior, restricts its use in extreme environments. In this study, we report a molecular-level design strategy for the preparation of a novel HNBR derivative containing pendant vinyl groups (HENBR-V-Cx) that combines enhanced low-temperature performance with post-functionalization potential. HENBR-V-Cx was synthesized via ring-opening and subsequent esterification of hydrogenated epoxidized nitrile butadiene rubber (HENBR) with unsaturated fatty acid monomers. This modular synthetic approach enables precise tuning of the side-chain architecture—including side chain length, grafting density, and molecular weight—allowing the glass transition temperature (Tg) to be reduced from approximately -20 °C to −40 °C, thereby significantly enhancing the low-temperature resistance while maintaining oil resistance. The pendant vinyl groups improved vulcanization efficiency, allowing high crosslink density and tensile strength (25.8 MPa) to be achieved with lower curing agent loadings. Furthermore, pendant vinyl groups also serve as reactive handles for post-functionalization. Fluorinated HENBR-V-Cx, obtained via cross-metathesis, exhibited improved hydrophobicity with a water contact angle (WCA) of up to 116°. A superhydrophobic coating with a WCA of up to 150.7° was fabricated by compounding fluorinated HENBR-V-Cx with nano-SiO₂, demonstrating strong potential for anti-corrosion and self-cleaning applications. This work establishes a versatile and expandable platform for HNBR modification, bridging molecular design with performance optimization and application-driven functionalities.