Mesomorphism Molecular Rigidity and Flexibility

Abstract

A novel homologous series of liquid crystalline (LC) behaviors of Schieff’s bases: RO-C6H4-CH=CH-COO-C6H4-N=CH-C6H4-OC2H5 have been synthesized and studied with a view to understand and establish the effect of molecular structure on LC properties of a novel substances. The members of a novel series are enantiotropically nematogenic (C1 to C10) or the some of the homologues (C12 to C18) are smectogenic phase nematogenic. Transition temperatures, textures and melting behaviors observed or determined by an optical polarizing microscopy equipped with a heating stage. Thermometric temperatures are varied between 102 °C and 311 °C. Textures of the nematic phases are threaded or schlieren and that of the smectic phases are of the type A or C. Smectic and nematic thermal stabilities are 122.5 °C and 270.7 °C. Total mesophase lengths vary from 111.0 °C to 194.0 °C. Analytical and spectral data confirms the molecular structures of homologues. Some LC properties o present novel series are compared with the structurally similar known series. Transition curves viz. Cr-M, Sm-N and N-I behaved in normal manner. N-I transition curve exhibited odd-even effect. Thus present novel series is partly smectogenic and fully nematogenic with high mesophase length and higher observed melting type