Synthesis and Characterization of Novel Thermotropic Liquid Crystals with a Lateral Chloro Group

Abstract

Twelve novel homologues having azolinkage of the series 4-Carbethoxy-[3′chloro-4′ (4″-n-alkoxy benzoyloxy)] azobenzenes has been synthesized. The methyl to n-hexyl homologues exhibit only a nematic mesophase, while the n-heptyl to n-dodecyl homologues exhibit both smectic and nematic mesophases. The n-tetradecyl and n-hexadecyl homologues exhibit only smectic mesophases. The plot of transition temperatures versus number of carbon atoms in alkoxy chain exhibits an odd-even effect for the nematic-isotropic transition temperatures. The mesogenic behavior of present series is explained by comparing its homologue with other homologue of related mesogenic series. The synthesized compounds were characterized by combination of elemental analysis and standard spectroscopic methods. For the exhibition of mesomorphic property the role of ester and azo linkages has been discussed. The impact of lateral chloro group on mesomorphism is also discussed.