Synthesis and Characterization of Some Boomerang Imine‐Ester Mesogenic Materials Based on Thiophene Unit

Abstract

A new homologous series of imine‐ester compounds ({(1E)‐[5‐(4‐nitrophenyl)‐2‐thienyl]methylene}amino)phenyl‐4‐alkoxybenzoate (series IIIa‐k) comprising thiophene ring as a rigid core has been synthesized. The molecular structures of these esters were proven by means of Fourier‐transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance (1H‐NMR, 13C‐NMR) and mass spectrometry (MS). Different liquid‐crystalline textures (nematic and smectic A) have been observed by optical polarizing microscopy (OPM) and differential scanning calorimetry (DSC) techniques. The first four homologues in this series (IIIa‐IIId) displayed a nematic phase while the most of homologues that have longer alkyl group exhibited both nematic and smectic phases. The liquid crystalline phases of these compounds are dependent on the length of alkyl chain of the molecules. The mesomorphic phase stability of the prepared compounds in the presence of thiophene ring within chemical structures of the mesogens has been discussed comprehensively, and the liquid crystalline behaviors of these compounds have been compared with other reported mesogens that have similar chemical structures.