Heat Capacities and Glass Transitions of 1-Propanol and Its Concentrated Solutions

Heat capacities of 1-propanol and its 80 wt% and 90 wt% solutions were measured by adiabatic calorimetry. For the quenched pure 1-propanol, a glass transition was observed at 98 K and an exothermic effect due to crystallization of 1-propanol was found above 130 K. For the annealed sample around 130 K, a fusion of 1-propanol crystal occurred at 148.6 K. On the other hand, the quenched 80 wt% and 90 wt% 1-propanol solutions exhibited phase separations and then glass transitions of the phase-separated 1-propanol at 101 K and 102 K, respectively, and exothermic effects due to crystallization of the 1-propanol above 130 K. In annealing these solutions around 130 K, fusion of the 1-propanol, incongruent melting of the phase-separated 1-propanol clathrate hydrate, and fusion of the phase-separated ice occurred at 144.5 K, 210.9 K, and 257.1 K, respectively, for the 80 wt% sample and fusions of the 1-propanol and the ice did at 144.5 K and 226.1 K, respectively, for the 90 wt% sample. All the glass transitions indicated KWW-type relaxations. From Arrhenius plots of the relaxation times for 1-propanol and its 80 wt% and 90 wt% solutions, the activation enthalpies were evaluated to be 23.6 kJ mol-1, 21.3 kJ mol-1, and 21.8 kJ mol-1, respectively.

(by E. Juszyńska & Y. Miyazaki)

	Fig. 1. Heat capacities of 1-propanol and its 80 wt% and 90 wt% solutions.
	Fig. 2. Spontaneous exothermic temperature drifts below glass transition temperatures for 1-propanol and its 80 wt% and 90 wt% solutions.