Effect of terminal metamers and homologous with imine and ester groups on mesomorphism and their DFT study

Abstract

ABSTRACT Three liquid crystalline series with different terminal chains have been prepared, where two of the series are metamer of each other, and all three series are homologues of each other in context to the terminal chain. All the homologues prepared were found to be enantiotropically mesogenic and were screened under a polarising optical microscope (POM). Differential scanning calorimetry (DSC) technique was used to obtain thermograms of phase transition, enthalpy and entropy change. Characterisation of all homologues was carried out by means of standard spectroscopic methods; infrared, proton magnetic resonance and ultraviolet spectroscopy. Series I n exhibited polymorphism as of smectic C, smectic A and nematic mesophases, while series II n and III n exhibit only smectic A and nematic mesophases. The geometry of all homologues was obtained using DFT calculation, and the effect of the twist angle of the aromatic ring on mesomorphism was examined. The effect of branching and length of the broken alkoxy terminal chain on the type of the mesophase was studied by comparing the terminal chain homologues. The prepared series were also compared with four structurally similar compounds to understand the effect of the relative position of groups and the effect of molecular length on thermal stability and mesophase length.