Thermodynamic Functions of a Liquid Crystal through Density Measurements

Abstract

Thermodynamic functions of a material are determined using ultrasonic measurements coupled with volumetric measurements at different temperatures. It is also possible to determine some of these thermodynamic functions using only volumetric measurements. Such studies are important in the case of liquid crystal as they give insight in the structural changes arising out of transition between two phases. Apart from this, these studies are also found to give clear information regarding the nature of phase transition, pre-transitional effects, and molecular ordering. Some of the thermodynamic functions calculated are adiabatic compressibility, order parameter, Sharma's number, etc. In the present study these different parameters have been determined using only volumetric measurements in case of 4,4 -azoxy anisole at different temperatures. Variations in various parameters with respect to temperature have been discussed in the light of the results obtained. In the literature the data for these parameters are available for the above said liquid crystal calculated in conjunction with ultrasound measurements. The results obtained in the present work are compared with these results. It has been shown that the variation of the properties observed with respect to temperature can be explained on the basis of Frenkal's heterophase fluctuation theory.