Dependence of Liquid-Crystal Behavior of a Substance on Molecular Structure

Abstract

A novel azoester homologous series of liquid crystals (LCs) consisting of 12 members has been synthesized and evaluated. All members of the series exhibit the nematic mesophase enantiotropically without the exhibition of a smectic mesophase. The textures of the nematic phase are threaded or Schlieren in type. The transition curves in the phase diagram behave in a normal manner. The N-I transition curves exhibit an odd-even effect. The analytical and spectral data support the molecular structures of the homologs. The transition temperatures and mesophase morphology were determined by an optical polarizing microscope equipped with a heating stage. The azoester compounds consist of three phenyl rings with a meta substituted ‒Cl group at the middle phenyl ring and –OR and ‒OCH₃ as terminal end groups. The average nematic thermal stability is 195°C and the nematogenic mesophase length ranges from 9°C to 186°C. The LC behaviors of the series are compared with a structurally similar series. The novel series is entirely nematogenic and of a high melting point type.

Keywords:

• Liquid crystal
• mesomorphism
• nematic
• odd-even effect

Acknowledgments

The authors are thankful to Head and Teaching staff of Applied Chemistry of Faculty of Technology and Engineering, M.S. University, Vadodara, for their valuable cooperation in the work. Authors are also thankful to CSMCRI, Bhavnagar, for the analysis of samples.