Alkoxy/halostyrylbenzoic acids were synthesized and evaluated for their mesomorphic and photophysical properties. The trans geometry of the molecules was established by the presence of large coupling constants in H-1-NMR spectra and confirmed further by X-ray diffraction (XRD) analysis of two of the compounds. The straight-chain acids were found fairly stable showing first sign of decomposition above 290 degrees C. The enantiotropic mesophases could only be studied in acids with seven or more methylene groups in the alkoxy chain. Textures of nematic and smectic phases were exhibited by these acids under polarizing optical microscope. Photophysical behavior of the compounds in solution was also investigated.
There is provided a carboxylic acid compound represented by the following formulae (I) to (IV): ##STR1## a liquid crystal material consisting of the carboxylic acid ester compound, a liquid crystal composition comprising the carboxylic acid ester compound, and a liquid crystal element using the carboxylic acid ester compound. There can be obtained advantages such as low operating temperature, high speed switching, very small electric power consumption, and high-stable contrast.