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 tem perature modulated DSC (TMDSC) and Brillouin spectroscopy ( BS) to investig ate the freezing behaviour of canonical glasses ( salol and di-n-butyl-phta late (DBP)) confined to controlled pore glasses (CPG) with pore diameters b etween 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 T-g as a static glass transition. In sma ller pores T-g is only slightly shifted to lower temperatures. This operati ve T-g is in good agreement with sound velocity data showing a sharp kink a t T-g. The working hypothesis of the existence of a static glass transition is supported by the fact that the alpha-relaxation process disappears with decreasing pore diameter. (C) 1999 Acta Metallurgica Inc.