Mesomorphism Dependence on Molecular Flexibility in an Azoester Series

Abstract

A novel azoester homologous series with a flouro terminal end group was synthesized and evaluated for mesomorphic properties. The novel homologous series consists of 12 members. The first two-third members of the series are nonmesogenic. The butyloxy to decyloxy homologues are enantiotropic nematogenic and the rest of the mesogenic homologoues are enantiotropic smectogenic only. Transition temperatures and textures of the mesophases were observed through an optical polarizing microscope equipped with a heating stage. The textures of the nematic phase are threaded or Schlieren as judged by a miscibility method and those of the smectic phase are of the type A or C. A phase diagram is used to illustrate the mesomorphic behavior across the series. Analytical and spectral data confirm the molecular structures of the homologues. Thermal stabilities of smectic and nematic mesophases are 114.3°C and 137.0°C respectively. The mesogenic phase lengths for smectic and nematic are vary from 8°C to 26°C and 26°C to 43°C respectively.