Induced Smectic A Phase through Intermolecular Hydrogen Bonding: Part XVIII: Influence of p-n-Alkyl Benzoic Acids on Thermal and Phase Behavior οf Hydrogen-Bonded Liquid Crystals

A novel series of intermolecular hydrogen bonded liquid crystals was synthesized with the mesogens of p-n-alkyl benzoic acids (nBA where n =5 to 10) and p-(p'-octyloxy benzylidene)-cyano aniline (OBCA) moieties. The thermal and phase behaviors of these mesogens (nBA:OBCA) are studied by thermal polarizing optical microscopy and differential scanning calorimetry techniques. Induced smectic A phase with focal conic fan texture is observed in all the synthesized compounds. Moreover, the nematic phase present in all the pure p-n-alkyl benzoic acids (nBA where n =6 to 10) is quenched in all the hydrogen bonded compounds (nBA:OBCA) and smectic A phase is induced. But, in the compound 5BA:OBCA the nematic phase is also present along with the induced smectic A phase. The structural elucidation pertaining to the formation and stabilization of intermolecular hydrogen bonding is carried out by a detailed IR spectral investigation.