Dielectric Relaxation Spectroscopy of Precipitated Silica and Elastomer-Silica Composites

The dynamics of hydration water at the interface of precipitated silicas is investigated by dielectric spectroscopy. Various experiments have been performed proving that the observed low temperature relaxation transition results from fluctuating water molecules. It is demonstrated that the mobility of the water molecules depends on the mean number of hydrogen bonds, which is governed by the amount of water at the silica interface. The effect of silanization on the relaxation strength and activation energy is analyzes for pure silica powder and elastomer-silica composites. This indicates that the polymer chains have a minor influence on the mobility of the water molecules.