On the Influence of Nano-Scaling on the Glass Transition of Molecular Liquids

The nature of the glass transition is still a matter of debate. We used temperature modulated DSC (TMDSC) and Brillouin spectroscopy ( BS ) to investigate the freezing behaviour of canonical glasses ( salol and di-n-butyl-phtalate (DBP)) confined to controlled pore glasses (CPG) with pore diameters between 2.5 and 20 nm. The temperature behaviour of the heat capacity of the composite system deviates from the bulk fluid properties and we interpret the remaining kink-like anomaly at Tg as a static glass transition. In smaller pores Tg is only slightly shifted to lower temperatures. This operative Tg is in good agreement with sound velocity data showing a sharp kink at Tg. The working hypothesis of the existence of a static glass transition is supported by the fact that the -relaxation process disappears with decreasing pore diameter.