Noncovalent Imidazolium Interphase Engineering of Carbon Black for Enhanced Reinforcement in Natural Rubber Composites

Carbon black (CB) reinforced natural rubber (NR) is central to tires, vibration damping, and sealing applications, yet its performance is limited by CB aggregation and insufficient filler–rubber interfacial wetting. Herein, we report an aqueous noncovalent imidazolium interphase engineering strategy for improving the reinforcement efficiency of industrial N330 carbon black in NR composites. 1-Butyl-3-methylimidazolium Bromide ([BMIM]Br) is preanchored onto N330 through cation−π/π–π interactions, forming a low-polarity interphase with outward-oriented butyl chains. This interphase reduces filler–filler cohesion, lowers the N330/NR interfacial tension by 69%, and increases the bound rubber content from 35.26% to 43.56%. As a result, the optimized NR/N330–3 composite delivers a tensile strength of 28.42 MPa, a 22% improvement, together with a 39% reduction in the Payne effect. This work provides a mild, aqueous, and nondestructive interfacial strategy for high-performance carbon-black-reinforced elastomer composites.