Density studies in p,p′-di-n-heptyloxy azoxy benzene

Abstract

The density p of p,p′-di-n-heptyloxy azoxy benzene is measured as a function of temperature from the isotropic liquid to the smectic-C phase. The compound exhibits enantiotropic smectic-C and nematic liquid-crystalline phases. The density changes across the phase transformations and the thermal expansion coefficient confirm the order of the transitions as of first order. An estimate of the pressure dependence of the nematic to smectic-C transition temperature showed that it obeyed the Clausius-Clapeyron equation, consistent with the reported literature. The pressure dependence of the nematic-isotropic transition temperature differs from the literature value, but is in agreement with the values reported for its lower homologues.