INTERPRETATION OF THE DYNAMIC HEAT-CAPACITY OBSERVED IN GLASS-FORMINGLIQUIDS

Slow structural relaxations can complicate the interpretation of therm odynamic measurements on glass-forming liquids. Here we demonstrate us ing model calculations that structural recovery can lead to an apparen t frequency-dependent heat capacity in ac calorimetry experiments. The model is shown to describe the complex heat capacity data reported in the literature for glycerol and poly(vinyl acetate). Importantly, the model does not invoke a complex heat capacity; rather, only static he at capacities are used. The analysis further suggests that ac calorime try should provide a powerful way of testing models of structural reco very. (C) 1997 American Institute of Physics. [S0021-9606(97)51544-3].