Mesomorphism Dependence on Positional Substitution of Same Polar Group on Same Phenyl Ring in Isomeric Homologous Series

Abstract

Novel homologous series 4-(4^′-n-alkoxy benzoyloxy) napthyl azo 2^′′ – nitro benzenes, consisted of eleven members of a series. All the eleven members (methoxy to tetradecyloxy) homologs are only enantiotropically nematogenic without exhibition of any smectogenic character. Transition temperatures and the textures are determined by an optical polarizing microscopy equipped with a heating stage. Textures of a nematic phase are threaded or schlieren. Analytical and spectral data supported the molecular structure of homologs. Transition curves viz., solid-nematic and nematic-isotropic showing phase behavior of the mesophase in a phase diagram behave in normal manner. Odd-even effect and alternation of transition temperatures are exhibited by N-I transition curve. N-I thermal stability is 129.7°C and Nematic mesophase vary from 12 to 64°C. Thus, novel series is entirely nematogenic and middle ordered melting type. Mesomorphic behavior of a novel series are compared with the structurally similar homologous series.

Keywords:

• Anisotropic
• liquid crystals
• monotropy
• nematic
• smectic

Acknowledgments

Authors acknowledge thanks to the Principal and the Management of M.V.M. Science and Home Science College, Rajkot for their valuable support and cooperation, as and when needed. Thanks are due to the CSMCRI Bhavnagar for analytical services and The M.S. Uni. of Baroda, Faculty of Tech. and Engg., Vadodara for providing microscopic facility by applied chemistry department.