Study of the molecular structure on liquid crystal properties with reference to thermotropic azoester derivatives

Abstract

ABSTRACTAn azoester homologues series: RO‒C6H4‒COO‒C10H6‒N˭N‒C6H4‒OC5H11 (para) as novel liquid crystalline (LC) materials has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties with reference to laterally substituted phenyl ring and terminally substituted ‒OR and ‒OC5H11 (n) groups; including ‒COO‒ and ‒N˭N‒ central bridges. Novel homologous series of thermotropic LC variety consists of thirteen homologues (C1 to C18). C1 to C3 derivatives are nonliquid crystal (NLC); C4 is only nematogenic and C5 to C18 are smectogenic plus nematogenic. All the mesogenic homologues (C4 to C18) are enantiotropically nematogenic or/and smectogenic as confirmed by a polarizing optical microscopy (POM) equipped with a heating stage. Transition curves Cr-I/M, Sm‒N, and N‒I behaved in normal manner in a phase diagram. Odd-even effect is exhibited by Sm‒N and N‒I transition curves. Analytical, spectral and thermal data confirms the molecular structure of novel homologues. Novel azoester series is predominantly nematogenic and partly smectogenic whose mesogenic temperatures ranges minimum to maximum from 79.0°C to 162.0°C. Thermal stability for smectic and nematic are 128.2°C and 147.7 °C, respectively. Thus, it is a middle ordered melting type of novel series whose total mesophaselength ranges from 20.0°C to 56.0°C. Textures of nematic are threaded or schlieren and that of smectic are smectic A or C.