Density studies across the smectic G-nematic and nematic-lsotropic transitions

The densities of N(p-n-pentyloxy benzylidene) p-ethylaniline and N(p-n-hexyloxy benzylidene) p-ethylaniline are measured as a function of temperature from the isotropic liquid to the smectic G phase. Both the compounds exhibit enantiotropic smectic G and nematic liquid crystalline phases. The changes in density across the phase transformations and the thermal expansion coefficient confirm the order of the transitions as of first order. The particular importance of the smectic G to nematic transformation is apparent from the density jump across the transition. An estimate of the pressure dependence of the isotropic-nematic transition temperature is found to be in reasonable accord with the literature data.