Thermal/photophysical properties of cyanobiphenyl based unsymmetrical molecules: synthesis and evaluation

Abstract

New set of mesogens based on cyanobiphenyl at one side and other side arms containing three or four phenyl rings linked through alkyl spacer and ester groups were synthesized via convergent approach. All the synthesized mesogens and their intermediates were structurally well characterized using FT-IR, 1H NMR, 13C NMR and CHNS analysis. The mesophase characterization carried out using the combination of hot stage polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The structural changes made in the mesogens i.e. increase of terminal chain length and aromatic groups with ester groups show decreasing the transition temperatures and phase stability to a wide temperature range. Nematic and smectic phases were observed for the mesogens with short/long terminal chain length.