Dependence of Mesomorphism on Molecular Rigidity

A novel smectogenic homologous series of twelve homologues synthesized and studied with a view to understand and establish the effect of molecular structure on liquid crystal properties (LC) and LC behaviors of thermotropic homologues. First (C1) to last (C16) member of a series exhibited only enantiotropically smectogenic property without showing nematic property which is absent even in the monotropic condition. Transition and melting temperature including textures of homologues were determined by an optical polarizing microscopy equipped with a heating stage, texture of a smectic phase are of the type A or C. Smectogenic phase length ranger between 5.1oC to 22.6oC. SmecticIsotropic (Sm-I) thermal stability is 153.55oC. Analytical, spectral and thermal data supported molecular structures of homologues. LC behaviors of present novel series are compared with the structurally similar homologous series. Transition curves viz. Cr-Sm and Sm-I transition curves of a phase diagram behaved in normal manner.