EFFECT OF MOLECULAR-STRUCTURE ON THE PHASE-BEHAVIOR OF SOME LIQUID-CRYSTALLINE COMPOUNDS AND THEIR BINARY-MIXTURES .1. 4-HEXADECYLOXYPHENYL-4'-CARBOXYBENZOATE AND 4-CARBOXYPHENYL-4'-HEXADECYLOXYBENZOATE

4-Hexadecyloxyphenyl-4'-carboxybenzoate (A) and 4-carboxyphenyl-4'-hex adecyloxy benzoate (B) were prepared and thermally characterized by po larized light microscopy and differential scanning calorimetry. Both c ompounds possess high transition temperatures indicating the formation of linear dimer molecules in the solid and liquid phases. The infrare d 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 w ere prepared and thermally characterized to construct the phase diagra m that showed a simple eutectic behaviour in the solid-mesophase trans itions, and a linear mesophase-isotropic transition temperatures. The latter behaviour was attributed to similar electronic factors in both molecules.