Thermodynamic aspects of the glass transition in liquids and plastic crystals

We outline the basic phenomena characterizing the glass transition, highlighting the intimate association of thermodynamic changes and relaxation times, and the limits set by the Kauzmann entropy crises. The relation between the Kauzmann temperature and the glass transition temperature is examined in relation to the strong and fragile classification of liquids, and a consistency between the parameters of the normalized VogelFulcher equation and the purely thermodynamic Kauzmann temperature is demonstrated. The separate roles of kinetic and thermodynamic factors in establishing the strong and fragile pattern are analyzed and the apparently anomalous position of the alcohols in the scheme is accounted for in these terms. Finally, the different types of excess heat capacity functions observed in different classes of glasses are reviewed, and some correlations with molecular structure are attempted.