Phase Transition Studies of the Liquid Crystal HpBBA

Abstract

Phase transitions of the liquid crystal N-(pn heptyloxybenzylidene)-pn-butylaniline (HpBBA) are investigated by specific-volume and ultrasonic-velocity measurements. A variation of the specific volume with temperature in all the mesophases confirms that the isotropic–nematic, nematic–smectic A, and smectic C–smectic G phase transitions are of first order, whereas the smectic A–smectic C one is of second order. All the phase transitions are confirmed by the variation of the ultrasonic velocity with temperature. The adiabatic compressibility (βad) and molar sound velocity (Rn) (Rao number) are deduced experimentally.