RELATION BETWEEN FREEZING-IN DUE TO LINEAR COOLING AND THE DYNAMIC GLASS-TRANSITION TEMPERATURE BY TEMPERATURE-MODULATED DSC

Temperature-modulated differential scanning calorimetry (DSC) allows f or the investigation of the glass transition in two different time sca les. One is related to the response on the periodic temperature pertur bation(10(-4) Hz < nu < 10(-1) Hz), the other to the vitrification due to cooling at a linear rate. The latter is equivalent to the glass tr ansition observed in DSC cooling experiments. By varying modulation fr equency and cooling rate it is possible to compare directly the corres ponding time scales. In the case of vitrification the frequency relate d to the cooling rate can be estimated. The results from different org anic and inorganic compounds are in agreement with the predictions of Donth's fluctuation approach to glass transition. (C) 1998 Elsevier Sc ience B.V. All rights reserved.