The heat capacities of isopropylbenzene were measured with an adiabatic calorimeter for the crystal from 14 to 177.13 K (Tm), for the glassy state from 14 to around 126 K (glass transition temperature: Tg) and for the liquid from Tg to 313 K, with a sample of 99.93% purity. The heat and entropy of fusion were found to be 7326 J mol−1 and 41.36 J K−1 mol−1, respectively. Based on these data, a set of thermodynamic functions are tabulated at rounded temperatures. In addition to the primary glass transition phenomenon, a secondary enthalpy relaxation as well as a step-like heat capacity anomaly was observed at around 70 K. These facts were discussed in correlation with the β-relaxation already observed by dielectric measurement. Gonfigurational entropies of the supercooled liquid and of the glassy state were calculated to investigate a relation with relaxational properties. The agreement is found between the temperatures where catastrophe occurs in viscosity (T0), and where the configurational entropy vanishes (T2). Finally, a kind of heat capacity break observed in the liquid state is discussed against the view that this behavior is compatible with a third-order thermodynamic transition.
No takes yet. Share an insight, caveat, or question.
Kishimoto et al. (1973) studied this question.