Mesomorphism and Molecular Structure of Ester Homologous Series Containing Carboxy and Vinyl Carboxy Linking Groups

Abstract

A novel homologous series 4-(4′-n-alkoxy benzoyloxy)-isopentyl cinnamates consisting of eleven homologs is reported. Mesomorphism commences from the hexyloxy homolog up to the hexadecyloxy homolog. The hexyloxy and hexadecyloxy derivatives are only enantiotropically nematogenic while, but the octyl, decyl, dodecyl, and tetradecyl homologs exhibit enantiotropic nematogenic and smectogenic mesophases. The rest of the homologs are nonmesogenic. The textures of nematic phase are threaded or Schlieren and that of the smectic mesophase is focal conic smectic A or C type. The transition curves of the phase diagram behave in a normal manner without the exhibition of an odd-even effect. Analytical and spectral data confirm the molecular structure of the homologs. Overall mesogenic phase temperature range varies from 11.0°C to 59.0°C. The average thermal stabilities of smectic and nematic are 122.25°C and 139.0°C, respectively. The series is predominantly nematogenic and partly smectogenic with a middle-ordered melting type and a considerable range of liquid crystallinity. Melting points and transition temperatures were determined using an optical polarizing microscope equipped with a heating stage. The mesomorphic properties are compared with structurally similar series.