DTA and p VT Measurements on 4-cyanobenzyI-5- (4-n-octyloxybenzoyloxy)-2-undecyloxybenzoate up to 250 MPa and 383 K

Abstract

Abstract The phase diagram of 4-cyanobenzyl-5-(4-«-octyloxybenzoyloxy)-2-undecyloxybenzoate (4CNOUB) has been established with differential thermal analysis (DTA). The pressure range for the smectic A phase is limited, resulting in a triple point at 165 MPa and 378.26 K. p, Vm, T data have been measured for the smectic and istotropic phases of 4CNOUB between 243 and 383 K and up to 250 MPa. The volume changes accompanying the crystal - smectic and scmectic - isotropic transitions have been deter-mined. The corresponding enthalpy changes have been calculated using the Clausius-Clapeyron equation. The p, Vm, T data enable also to estimate the volume entropy for the smectic - isotropic transition and the volume dependence of the clearing temperature.