Mesomorphism in binary mixtures of 4-((hexylimino)methyl)benzoic acid and 4-alkyloxybenzoic acids

A new non-mesogenic Schiff-based carboxylic acid, viz. 4-((hexylimino)methyl)benzoic acid (HIMB), is synthesized and is used to prepare the binary mixtures with mesogenic 4-n-alkyloxybenzoic acids (nOBAs, where n = 3, 4, 5, 7, 8, 9 and 12) in 1:1 molar ratio. The mesomorphism in HIMB and nOBA mixtures is studied by polarizing optical microscopy and differential scanning calorimetry. The mesomorphic thermal stabilities of these mixtures are found to vary with those of the nOBAs. The results are discussed with the reported mixtures of nOBAs with other Schiff-based pyridyl moieties, which are found to exhibit new phase variants and mesomorphic thermal stabilities. The phase transition temperatures and the enthalpy changes at the phase transitions are discussed in comparison with the other similar binary mixtures. The effects of intermolecular interactions on mesomorphism are discussed.