Dependence of Liquid Crystalline Behaviors on Molecular Flexibility

Abstract

A novel homologous series of thermotropic liquid crystal (LC) has been synthesized with a view to understand and establish the effect of molecular structure on liquid crystal behaviors of a series. The present LC series consist of twelve homologues (C 1 to C 16 ); whose mesomorphic properties commence from octyloxy (C 8 ) homologue of a series. C 8 , C 10 and C 12 members of a series are monotropic smectic and C 14 , C 16 members are enantiotropically smectogenic. C 1 to C 7 homologues are nonmesomorphic. Nematogenic property is totally absent. Transition and melting temperatures are determined by an optical polarizing microscopy equipped with a heating stage. Textures of smectic mesophases are focal conic three or two dimensional networking of the type A or C. Cr-I/Sm and Sm-I or I-Sm transition curves behaved in normal manner. Analytical and spectral data confirms the molecular structures of homologues. Thermal stability of smectogenic mesophase is 100.6 o C and mesomorphic phase length is very short (12.9 o C to 15.3 o C). LC properties of a present novel series are compared with the structurally similar homologous series. Present series is partly smectogenic and partly non mesomorphic with poor degree of mesomorphism and middle ordered melting type without exhibition of nematogenic behavior.