Enthalpy and dielectric relaxations in supercooled methyl m -toluate

Abstract

The structural relaxation of a glass forming liquid, methyl m -toluate, is studied in the deeply supercooled region near glass transition with the calorimetric and dielectric techniques. The thermodynamics and kinetics of the enthalpy relaxation are focused, and the kinetic studies are paralleled with dielectric relaxation. Relaxation enthalpies are expressed in two manners, and the numerical determination is based on the quantity of heat involved in the enthalpy recoveries from the relaxed glasses to liquids through glass transition. The correlations between the relaxation enthalpies and fragility are examined, and the remarkable dependence is visible for both cases. The enthalpy and dielectric relaxations in the liquid reveal comparable results of the fragility indices and stretching exponents. © 2009 American Institute of Physics.