Mesomorphism Dependence on Molecular Flexibility by –OCH₃ and –H Terminal Units

Abstract

A novel ester homologous series: 4-(4’-n-Alkoxy benzoyloxy)-4”-methoxy benzyl cinnamates have been synthesized and studied with a view to understanding and establishing the dependence of liquid crystal behavior on molecular structure. The novel series of eleven homologues is entirely nematogenic without exhibition of any smectogenic character from the very first member of the series. Transition and melting temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curves of a phase diagram show the mesomorphism, which behaves in normal manner. An odd-even effect is exhibited by the nematic–isotropic transition curve. The textures of the nematic mesophase are threaded or schlieren in type. Analytical and spectral data confirm the molecular structures of the novel homologues. Thermal stability for the nematic phase is 211.5°C and the degree of mesomorphism varies from 17°C to 72°C and it is a high melting type series. Mesomorphic properties of the series are compared with structurally similar series.

Keywords:

• Liquid crystals
• mesomorphism
• mesomorphs
• nematic
• smectic

Acknowledgments

The authors acknowledge thanks to the Green Circle Inc. Lab for research facilities services as and when needed. The authors also thank Dr. Umed Bhoya for his valuable helping hand and microscopic facility. Thanks are due to the Sophisticated Analytical Instrumentation Facility, Punjab University, Chandigarh for analytical services.