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

ABSTRACT

An 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.

KEYWORDS:

• Azoester
• nematic
• mesomorphism
• smectic
• thermotropic

Acknowledgments

Authors acknowledge thanks to Dr. R. R. Shah, principal of K. K. Shah Jarodwala Maninagar Science College, Ahmedabad. Authors are thankful to Dr. A. V. Doshi, Ex-principal of M.V.M. Science and Home Sci. College - Rajkot for his constant support, inspirations, valuable comments, suggestions, and help, as and when needed during the course of present investigation. Authors Acknowledge thanks to NFDD Centre for the analytical and spectral services.