Optimizing Graphene Oxide/NBR Nanocomposites Through Interfacial Hydrogen Bonding for Enhanced Mechanical, Dielectric, and Optical Performance ^†

The development of high-performance elastomer nanocomposites increasingly depends on engineering the filler–matrix interphase rather than maximizing filler content. This study examines nitrile butadiene rubber (NBR) reinforced with 0.5–2.0 phr graphene oxide (GO) synthesized via a modified Hummers’ method, focusing on how hydrogen-bonded interfaces influence structural, mechanical, dielectric, and optical behavior. GO, rich in hydroxyl, carboxyl, and epoxide groups, was incorporated through a solution–coagulation process followed by sulfur vulcanization to promote uniform dispersion. X-ray diffraction confirmed effective GO exfoliation, with maximum polymer chain ordering at 1 phr. FTIR spectra showed broadening/redshift of the nitrile band and GO-derived C–O–C and C–O absorptions, evidencing hydrogen bonding and dipole–dipole interactions without covalent grafting. Microscopy and AFM revealed optimal dispersion and a narrowed nanostructure size range (20–45 nm) at 1 phr. UV–Vis/Tauc analysis demonstrated a non-monotonic band gap trend (direct, e.g., 3.01 → 3.13 → 3.11 eV), arising from competition between quantum confinement and π–π stacking. Dielectric spectroscopy (10²–10⁶ Hz, 20–100 °C) indicated improved permittivity stability via Maxwell–Wagner–Sillars polarization, with 1 phr achieving the most balanced response. Mechanical testing showed gains in tensile strength, tear resistance, rebound elasticity, abrasion resistance, and solvent resistance, alongside enhanced rubber–metal adhesion and thermo-oxidative stability. Across all analyses, 1 phr GO emerged as the optimal loading, offering a percolating yet well-dispersed interphase that maximizes property transfer while avoiding aggregation-driven losses. The results highlight interphase engineering as a scalable strategy for producing durable, dielectric-stable elastomers for sealing, oil-resistant, and industrial applications.