New Silica/Polymer Coupling by the Use of Cation–π Interactions

Silica-filled styrene–butadiene rubber (SBR) compounds are state-of-the-art materials to produce tire treads. This is based on their good dynamic mechanical properties, resulting in a high wet grip and low rolling resistance. The application of silica as a filler requires the addition of a silane coupling agent that facilitates the chemical coupling to the rubber molecules, reducing filler–filler interactions in favor of filler–rubber interactions. However, the current solutions are based on the formation of strong covalent bonds between silica and rubber. This results in certain drawbacks; for example, if the silica–rubber covalent bond is broken, it is unlikely to be reformed, leading to a continuous deterioration of the dynamic properties of the rubber compound. Also, recycling of such compounds is challenging due to the presence of these chemical silica–rubber bonds. This research aims to face these issues by implementing an alternative coupling system based on cation–π interactions, which exhibit a reconnectable nature. To achieve this, three different quaternary ammonium compounds were grafted on the silica surface to interact with the aromatic rings of the SBR. These modifications resulted in improved dynamical mechanical properties, superior dispersion, and improved fatigue behavior of a tire tread compound. However, it also leads to a decrease in the mechanical performance of these compounds.