As glasses are nonergodic systems, their properties should depend not only on external macroparameters, such as P and T, but also on the time of observation and thermobaric history. In this work, comparative ultrasonic studies of two groups of molecular propylene carbonate glasses obtained by quenching from a liquid at pressures of 0.1 and 1 GPa have been performed. Although the difference in the densities of the different groups of glasses is small (3-5%), they have significantly different elastic properties: the difference in the respective bulk moduli is 10-20%, and the difference in the respective shear moduli is 35-40% (!). This is due to the "closure of nanopores" in the glass obtained at 1 GPa. The pressure and temperature derivatives of the elastic moduli for these groups of glasses are also noticeably different. The glass-transition temperatures of glasses from different groups differ by 3-4 K. The character of absorption of ultrasound waves near the glass-transition temperature also differs for different groups of glasses. The differences in the behaviors of these groups of glasses disappear gradually above the glass-transition temperature, in the region of a liquid phase. Glasses with a wide diversity of physical properties can be obtained using various paths on the (T,P) diagram.
We compare elastic properties of the liquid and glassy glycerol and propylene carbonate as the archetypal molecular glass formers with and without hydrogen bonding.
The elastic properties of 1-Chloroadamantane and 1-Bromoadamantane in order–disorder and order–quasi-order phase transitions at temperatures in the range of 77–305 K and high pressures up to 1.1 GPa are studied...
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