Glass transition and thermal expansivity in silica-polystyrene nanocomposites

The glass transition temperature Tg and the thermal expansion coefficient have been measured using the capacitive scanning dilatometry for silica-polystyrene (PS) nanocomposites with various silica volume fraction up to 50 vol.%. The glass transition temperatures for silica-PS nancomposites show a deviation from the bulk Tg together with a large scatter. Thermal expansivity decreases with increasing silica fraction both below and above Tg. A clear relaxation peak can be observed in the expansivity–temperature curve for silica-PS nanocomposites. The intensity of the peak decreases with increasing silica fraction. The decrement is larger than the value expected on the assumption that silica particles do not participate in the glass transition.