CALORIMETRIC STUDY OF 1,3-DIPHENYL-1,1,3,3-TETRAMETHYLDISILOXANE - EMERGENCE OF ALPHA-GLASS, BETA-GLASS, AND CRYSTALLINE-GLASS TRANSITIONS

Heat-capacities of fragile liquid 1,3-diphenyl-1,1,3,3-tetramethyldisi loxane (PMS) were precisely measured in the temperature range between 13 K and 300 K with an adiabatic calorimeter, alpha- and beta-glass tr ansitions were observed at around 167 K and 69 K, respectively, in the liquid state, and another glass transition at around 150 K in the sta ble crystalline state, PMS was thus found to be guile a rare substance to show glass transitions both in the liquid and crystalline states i n one substance. The interrelation between the transition temperatures is discussed with respect to their modes of molecular motions.