NOVEL DIFFERENTIAL SCANNING CALORIMETRIC STUDIES OF SUPERCOOLED ORGANIC LIQUIDS

The glass-forming tendency of a large number of organic liquids of varying molecular shapes has been examined using differential scanning calorimetry (DSC) and a sharp distinction between spherical and non-spherical molecular liquids as regards their glass-forming efficiency is observed. Calorimetric evidence has been presented for the first time to show that the glass-transformation process in monohydroxy alcohols is a combination of two processes. The DSC technique has also been used for the first time to detect the so called beta-process below the glass-transition temperature, T(g). In view of the prominence of recent mode-coupling theories (MCT), a critical examination of supercooled liquids in the temperature region (1.2-1.3) T(g) has been carried out, and this has revealed a small third-order thermodynamic transition temperature, T11, located distinctly below the critical temperature, T(c), of the MCT. A detailed discussion of the significance of the temperature T11 is given.