Effects of Different Terminal Substituents on the Mesomorphic Behavior of Some Azo-Schiff Base and Azo-Ester-Based Liquid Crystals

Abstract

In order to investigate the influence of the terminal substitution on mesomorphism, two new series of azo-Schiff base and azo-ester liquid crystals having the following structures have been synthesized. All the compounds possess mesomorphic properties. In series A compounds A₁ and A₃ exhibit only a nematic mesophase, whereas compounds A₂, A₄, A₅, A₆, A₇, A₈, A₉, and A₁₀ exhibit a smectic as well as a nematic phase. In series B compounds B₁ to B₉ exhibit only a nematic mesophase, and compounds B₁₀ and B₁₁ exhibit a smectic as well as a nematic phase, but compound B₁₂ exhibits only a smectic phase. All these compounds were characterized by elemental analyses and spectroscopic techniques (Fourier transform infrared [FTIR], ¹H nuclear magnetic resonance [NMR], and mass spectroscopy). Their mesomorphic properties were measured by optical polarized light microscopy and differential scanning calorimetry (DSC).

Keywords:

• Azo
• azo benzene
• ester
• mesophase
• nematic
• smectic

Acknowledgment

We are thankful to Solvay Chemicals Ltd., Ankleshwar (Gujarat), for providing thermal studies (DSC) and the Department of Applied Chemistry, Faculty of Technology and Engineering, M. S. University of Baroda, Vadodara, for providing us with an optical polarizing microscope for mesophase studies.

Notes

^a Monotropic mesophase.