Engineering Multiple Alkoxyls into Elastomeric Oligomers toward Novel Interfacial Regulator of Rubber/Silica Composites

Decorating a rubber backbone with alkoxyl groups has been exploited as an effective pathway to regulate the interfacial affinity of rubber/silica (SiO2) composites. However, conventional decoration methodologies, whether it is copolymerization with functional monomers or postfunctionalization of the main chain, are still limited by specific catalytic/reaction systems and complex processes. In this study, a series of alkoxyl-functionalized rubber oligomers were successfully prepared upon the dynamic covalent polymerization reaction between vinylsilane and di/polysulfide linkages in vulcanizates, simultaneously achieving network disintegration and the insertion of vinylsilane with pendent alkoxyl handles. Accordingly, the obtained oligomers possess a unique chain structure involving multiple alkoxyl handles and rubber-based segments; the former contributes to increasing the covalent coupling probability with SiO2, while the latter can suppress the spontaneous agglomeration between adjacent SiO2 through a physical shielding of the polar SiO2 surface. Moreover, the rubber-based segments can also participate in the cross-linking of the composites, thereby significantly improving the dispersion state of SiO2 and the interfacial affinity in the resulted composites. Accordingly, incorporating the obtained oligomer can achieve superior “magic triangle” properties of rubber/SiO2 composites at significantly lower alkoxyl content compared to conventional silane Si69. More importantly, the structural effects of the obtained oligomer on the SiO2 dispersion and interfacial affinity of the composites were explored in detail, which provides fundamentals for disclosing the interfacial coupling mechanisms and directing the optimization design of “green tires” with superior performance.