Analysis of hydrogen-bonded liquid crystals formed between nitro-substituted benzoic acid and p-n-alkyloxy benzoic acids

A novel series of hydrogen-bonded liquid crystals (HBLC) comprising of eight mesogenic complexes are formed between 3-Nitrobenzoic acid (NBAO) and p-n-alkyloxy benzoic acids (nBAO). The formation of inter molecular hydrogen bonding is evinced through FTIR spectra. Mesogenic phases are confirmed through the textural observations made by Polarizing Optical Microscope (POM) and their transition temperatures are correlated with the data obtained from Differential Scanning Calorimetry (DSC) studies. Phase diagram is constructed from POM and DSC studies. Odd-even effect has been evinced in the transition temperature and enthalpy values corresponding to the smectic C phase transition. Optical tilt angle in smectic C phase is fitted to a power law which reveals that the temperature variation of the tilt angle measurement follows the Mean Field theory predicted value. Thermal stability factor for the individual phase is also elucidated. Dielectric dispersion curves are obtained for the complexes exhibiting nematic phase.