Molecular Crystals and Liquid Crystals, Vol.642, No.1, 1-8, 2017
Role of molecular structural flexibility on mesomorphism
A homologous series of novel chalconyl ester derivatives: RO.C6H4.COO.C6H4.CO.CH:CH.C6H4.OC6H13(n) shave been synthesized and studied for its thermotropic liquid crystal (LC) properties with a view to understanding and establishing the relation between molecular structure and LC properties. The homologous series consists of eleven members whose, mesomorphism commences from C-3 of the series and continues up to the C-16 homologue. The C-1 and C-2 homologues are nonliquid crystals. All the LC homologues are enantiotropically nematogenic with absence of smectogenic character. Transition temperatures were determined by an optical polarizing microscope (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Analytical and spectral data confirms the molecular structures of homologues. Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibits an odd even effect; descended at C-10 homologue and then again rises at C-12 and descended from and beyond C-12 homologue. Thus it partly deviates from normal behaviour. Thermal stability for nematic is 95-89 degrees C and nematogenic upper and lower mesophase lengths are 41.0 degrees C and 07.0 degrees C respectively. Group efficiency order for nematic on the basis of thermal stability is -OC8H17(n)> -OC6H13(n) > -OC10H21(n) and it is a low order melting type series.