Construction of ion bonds in gel-free polydiene-based ionomers without compromising molecular weight

Rubber-based ionomers have attracted extensive research interest from academy and industry attributing to their distinct physical mechanical properties. However, currently reported approaches to performing polar modification on common tire rubber (such as natural rubber and butadiene rubber) typically demonstrate high gel fraction or low molecular weight. Herein, we prepared a gel-free rubber-based ionomer by the first epoxidation to elastomeric polymers and subsequent olefin metathesis reaction, which showed no degradation of molecular weight. Meanwhile, to investigate the reaction mechanism of epoxidation and olefin metathesis, high vinyl polybutadiene rubber (HVBR) with multi-site reactive units was used as the matrix. Experimental results showed that the incorporation of epoxy groups could effectively reduce the degradation of HVBR matrix caused by the olefin metathesis. The formation of multiple ion pair and ion cluster structures could significantly enhance the mechanical strength and damping properties of HVBR-based ionomers. And the dynamic measurements indicated that the increased skidding resistance and reduced rolling resistance of HVBR-based ionomers were also realized. It was acknowledged as a considerable challenge to simultaneously enhance these properties. The strategy developed here suggests a feasible pathway toward high-performance “green” tires with low noise, superior comfort and excellent auto-braking performance.