抄録
The ultrasonic and viscous behaviour of cholesteryl stearate which exhibits multiple mesophase transitions is studied. The variation of ultrasonic velocity (V), adiabatic compressibility (βad), molar sound velocity (R), viscosity (η) and flow activation energy (Ev) with temperature have been studied in the isotropic, cholesteric and smectic mesophases. The velocity measurements are carried out with a fixed-path double-crystal interferometer and viscosities are measured by a cone-and-plate viscometer within a narrow range of shear rate. The adiabatic compressibility shows abrupt decrease in the vicinity of the thermodynamic transitions between the smectic, cholesteric and isotropic states. The plot of logη vs (1000/T) exhibits changes in slopes at the smectic-cholesteric and cholesteric-isotropic transitions. The activation energy for viscous flow is computed. The ultrasonic velocity data in this liquid crystal is reported for the first time.
