EFFECT OF MOLECULAR-STRUCTURE ON THE PHASE-BEHAVIOR OF SOME LIQUID-CRYSTALLINE COMPOUNDS AND THEIR BINARY-MIXTURES - III - BINARY-MIXTURES OF ALKOXYPHENYL ARYLATES AND ARYLALKOXYBENZOATES

4-Substituted phenyl-4-hexadecyloxybenzoates and 4-hexadecyloxyphenyl- 4-substituted benzoates were prepared and thermally characterized by d ifferential scanning calorimetry. Transition temperatures were identif ied by polarized-light microscopy. Substituents were chosen to cover a wide range of electronic and dipolar characteristics. Binary mixtures of different components were prepared and similarly characterized to construct their phase diagrams. In mixtures of the 4-CN and 4-NO2 anal ogues, enhanced SmA mesophases were found when either of these esters was mixed with one of the methoxy analogues. A weak molecular complex is proposed to account for this non-ideal solution behaviour. Linear o r slightly enhanced mixture behaviours were found for the nitro or cya no derivatives when mixed with each other. The results are interpreted in terms of electronic, dipolar, and molecular interactions.