Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their binary mixtures. I. 4-Hexadecyloxyphenyl-4-carboxybenzoate and 4-carboxyphenyl-4-hexadecyloxybenzoate

4-Hexadecyloxyphenyl-4-carboxybenzoate ( A ) and 4-carboxyphenyl-4-hexadecyloxy benz- oate ( B ) were prepared and thermally characterized by polarized light microscopy and differential scanning calorimetry. Both compounds possess high transition temperatures indicating the formation of linear dimer molecules in the solid and liquid phases. The infrared data support the conclusion that the alkoxyphenyl carbonyl unit in A is more polarizable and hence stabilizes the intermolecular packing, thus leading to enhanced mesogenicity. Mixtures of the two compounds were prepared and thermally characterized to construct the phase diagram that showed a simple eutectic behaviour in the solid-mesophase transitions, and a linear mesophase-isotropic transition temperatures. The latter behaviour was attributed to similar electronic factors in both molecules.