Glass transition and mixing thermodynamics of a binary eutectic system

Abstract

A quantitative evaluation of the contribution of mixing thermodynamics to glass transition is performed for a binary eutectic benzil and m-nitroaniline system. The microcalorimetric measurements of the enthalpy of mixing give small and positive values, typically ∼200 J mol⁻¹ for the equimolar mixture. The composition dependence of the glass transition temperature, T_g, is found to show a large and negative deviation from the ideal mixing rule. The Gordon–Taylor and Couchman–Karasz models are subsequently applied to interpret the T_g behavior, however, only a small fraction of the deviation is explained. The analyses of the experimental results manifest quantitatively the importance of the mixing thermodynamics in the glass transition in miscible systems.