Novel differential scanning calorimetric studies of supercooled organic liquids

Abstract

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 β-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.