Atomistic Descriptions of the cis-1,4-Polybutadiene/Silica Interfaces

Since the early 1940s, silica has been increasingly used in tire compounds as a complement to carbon blacks. The use of silica offers substantial benefits in tires, such as a low rolling resistance and a better grip on wet and icy roads. Nevertheless, coupling agents must be used to enable the mixing with rubber. The understanding of the action of silica in the reinforcement process and the role of the coupling agents at the molecular level requires the investigation of the interfacial region of the silica surface interacting with polymer chains. We report here detailed atomistic simulations of the interfacial region between different silica surfaces and cis-1,4-polybutadiene polymer chains. We describe the interfacial regions in terms of density and the radius of gyration component profiles along the normal to the substrate. We investigate how the nature of the silica surface, the surface density of silanols, and the surface coverage of grafted polymer chains and grafted OCTEO impact the molecular arrangements of the interfacial zone and the local properties of polymer chains.