Study of deviation from normal liquid crystal behavior of mesomorphic-isotropic transition curve in a chalconyl ester series with equipolar terminal end groups

ABSTRACT

A novel chalconyl ester homologous series RO.C₆H₄.COO.C₆H₄.CO-CH:CH-C₆H₄.OC₈H₁₇(p) synthesized and studied with a view to understanding and establishing the relation between molecular structure and Liquid Crystal (LC) properties of thermotropic mesomorphs. The novel series consists of eleven homologous (C₁ to C₁₆). Enantiotropicnematic type of mesophase formation commences from C₃ homologue and continued up to the last C₁₆ homologue of a novel series. Smectogenic character is totally absent for the novel series. Transition temperatures and the textures of nematic phase were determined through an optical polarizing microscopy (POM) equipped with a heating stage. Textures of nematic phase are threaded or Schlieren. Transition curve Cr-N/I and N-I behaved in normal manner except C₈ homologue which showed negligible deviation from normal behavior. N-I transition curve exhibited odd–even effect. Analytical and structural data supported the molecular structures of homologues. Average thermal stability for nematic is 98.88°C whose degree of mesomorphismvary from 12.0°C to 37.0°C. Evaluated thermometric data of present novel series are compared with structurally similar series. Group efficiency order for nematic on the basis of thermal stability, early commencement of mesophase and the degree of mesomorphism. Thus, present series is predominantly nematogenic and lower middle ordered melting type the low degree of mesomorphism.

KEYWORDS:

• Enantiotropy
• liquid crystal
• nematic
• smectic
• thermotropic

Acknowledgments

Authors acknowledge thanks to Dr. N.N. Vyas, the head of chemistry department and the principal of the college for their supportive view and providing research facility of present investigation. Authors are also thankful to Dr. A.V. Doshi, Ex. Principal, M.V.M. Science and Home. Sc. College, Rajkot for his valuable cooperation and support throughout this present investigation. Authors acknowledge thanks to Dept. of Chemistry, S. P. University, Vidhyanagarfor analytical and spectral series.