Relaxation Dynamics of Hydration Water at Activated Silica Interfaces in High-Performance Elastomer Composites

The dynamics of hydration water at the silica interface of elastomer (S-SBR) composites filled with various types of silica with and without activation by silane is investigated by broadband dielectric spectroscopy. This gives some new insight into the mechanisms of silane coupling and polymer−filler interaction in silica-filled high-performance elastomers. Depending on the hydration level of the silica, water islands or complete coverage of the silica surface with at least one monolayer of water are identified by the dielectric response. The observed two low-temperature relaxation transitions are shown to be related to fluctuations of physically adsorbed water (SP1) and of hydroxyl groups (SP2), respectively, differing in relaxation strength and activation energy. The relaxation strength of the main peak SP1 decreases with silanization, indicating that, due to hydrophobization of the silica surface, part of the adsorbed water migrates into the rubber matrix. At low surface coverage, below one monolayer o...