Molecular Crystals and Liquid Crystals, Vol.562, 177-190, 2012
Dielectric and Optical Studies in Smectic C of A Novel Hydrogen Bonded Liquid Crystal Homologous Series
A novel hydrogen bonded liquid crystalline series comprising of p-n alkyloxy benzoic acids is isolated. This series include seven complexes in which hydrogen bond is formed between undecyloxy benzoic acid and various homologues of benzoic acid varying from pentyl to dodecyloxy carbon number. All the homologues of the present series show rich mesomorphism exhibiting orthogonal and tilted phases. The formation of the hydrogen bond is confirmed by Fourier transform infrared spectroscopy studies. Transition temperatures and corresponding enthalpy values along with enantiotropic and monotropic transitions are elucidated from differential scanning calorimetry thermograms. Polarizing optical microscopy revealed various phases in the form of textures. An interesting observation is the identification of a new smectic ordering labeled as smectic X which is sandwiched between traditional nematic and convectional smectic C phases. Dielectric relaxations in smectic C phase of three homologues have been analyzed and the activation energy is calculated from respective Arrhenius plots.