HEAT-CAPACITIES AND GLASS TRANSITIONS OF GROUND AMORPHOUS SOLID AND LIQUID-QUENCHED GLASS OF TRI-O-METHYL-BETA-CYCLODEXTRIN

Amorphous solid of tri-O-methyl-beta-cyclodextrin (TMCD) was formed by grinding crystalline samples with a vibrating mill at room temperature. Heat capacities of the ground amorphous solid (GAS), liquid-quenched glass (LQG) and crystal of TMCD were measured with an adiabatic calorimeter in the temperature range 13-375 K. The heat capacity of the GAS was the same as the LQG in the whole temperature range. The glass transition was observed at 345 K for both amorphous solids. The heat capacities of the crystal were similar to 3% lower than those of the amorphous solids. During the heat capacity measurement of the LQG, a typical exothermic effect due to the enthalpy relaxation was observed in the temperature range 315-345 K. On the other hand, much larger enthalpy relaxation having unusual temperature dependence occurred for the GAS in the same temperature range. The released configurational enthalpy of the GAS was more than twice that of the LQG.