Effect of Equipolar Endgroup of a Molecule on Mesomorphic-Isotropic Transition Curve

Abstract

A Homologous series:RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-OC18H37(n) (para) of chalconyl novel ester of dual character as thermotropic and lyotropically bioactive is synthesized and studied with a view to understand and establish the relation between mesomorphism and molecular structure on the basis of molecular rigidity and flexibitity through thermotropic liquid crystalline (LC) state. Novel series consists of thirteen homologues of which four homologues (C1 to C4) are non liquid crystal (NLC) and the rest of the homologues (C5 to C18) are thermotropically enantiotropic nematic without exihibition of smectic property. Thermometric transition temperatures and textures of nematogenic phase are determined by an optical polarizing microscopy equipped with a heating stage (POM).Textures of nematic phase are threaded or schilieren. Transition temperatures of novel homologues are relatively lower than the transition temperature of corresponding dimeric trans n-alkoxy cinnamic acid. Cr-N/I and N-I transition curves behaves in normal manner with negligible abnormality at C18 homologue in phase diagram of a series.Analytical and spectral data conforms the molecular structure of homologues. Thermal stability for nematic is 121.88°C whose degree of mesomorphism vary minimum from 4.0°C to a maximum of 34.0 °C, and hence novel series is of middle ordered melting type, Group efficiency order for-OC18H37 tail groups (series-1&Y) is highest irrespective of type of ester group –COO-and CH=CH-CO derived for nematic.