Dependence of mesomorphism on flexibility of lateral and terminal groups of chalconyl esters

Abstract

ABSTRACTA novel liquid crystalline homologous series of chalconyl vinyl esters with a lateral bromo substituent RO─C6H4─CH═CH─COO─C6H3─(Br)─CO-CH═CH─C6H4─C12H25(n) has been synthesized and studied with a view to understanding and establishing the relation between the molecular structure and liquid crystal (LC) behavior in terms of molecular flexibility of the lateral and terminal groups. The novel homologous series consists of thirteen (C1–C18) homologues, whose enantiotropic nematic and smectic mesomorphism commences from the C4, (C4–C18) and the C5, (C5–C18) homologue, respectively. The rest of the homologues (C1, C2, C3) are nonliquid crystals (NLC). Mesomorphism and transition temperatures were examined using an optical polarising microscope (POM) equipped with a heating stage. Textures of nematic phase are threaded or Schlieren and those of the Smectic-A or Smectic-C are focal conic. Analytical, thermal and spectral data supported molecular structures of the novel homologues. Thermal for smectic and nematic are 87.5°C and 101.1°C, respectively, whose, total mesophase length ranges from 17°C to 30°C at C14 and C7 homologue, respectively. The mesomorphic transition temperature ranges are between 70°C and 113°C.