Characterization of a new smectic ordering in supramolecular hydrogen bonded liquid crystals by X-ray, optical and dielectric studies

Abstract

A novel series of linear supramolecular hydrogen bonded liquid crystals (SMHBLC) has been investigated. Complimentary hydrogen bonds are formed between various alkyloxy benzoic acids. Formation of hydrogen bond is confirmed by FTIR spectroscopic studies. These homologs exhibit rich phase variance as evinced by various textures by polarizing optical microscopic (POM) studies. DSC studies revealed the transition temperatures and corresponding enthalpy values which are elucidated from the DSC thermograms. Phase diagram has been constructed through POM and DSC data. An interesting finding is the observation of a new smectic ordering labeled as smectic X. This phase has been characterized by various techniques which includes XRD. Optical tilt angle in smectic C and smectic X phases of various homologs has been measured and fitted to a power law. Dielectric relaxations have been carried out in nematic and smectic C phases of different mesogens and their activation energies are calculated. An interesting observation is the optical shuttering action of the mesogens in the nematic phase. In addition to the above phenomenon the light filtering action of these mesogens in the nematic phase has been studied.