H-shaped symmetrical twin liquid crystalline compounds with polar-terminal substituents

Abstract

The conventional H-shaped symmetrical dimeric liquid crystalline compounds were synthesised and their thermotropic properties were studied by hot-stage of a polarising microscope. These compounds consist of azoester–ether mesogenic unit with different polar-terminal substituents (–NO₂ and –Cl) for series I and series II, interconnected through flexible spacer (n = 4) via ether linking unit to itself at the lateral hydroxyl position of azoesters. All these compounds were characterised by combination of elemental analysis and standard spectroscopic methods. These compounds were found to exhibit monotropic smectic A or smectic C and/or unknown smectic X mesophases. The effect of different terminal substituents on mesomorphism is discussed.

Keywords:

• H-shaped azoester dimers
• ether–ester linkage
• flexible spacers
• smectic mesophases

Acknowledgements

The authors are thankful to the dean, Faculty of Technology and Engineering, and head, Applied Chemistry Department, for providing the research facilities. The authors are also thankful to Prof. Sandeep Kumar, Raman Research Institute, Bangaluru, for his constructive suggestions and fruitful discussions. One of us (AKP) is grateful to the University Grants Commission, New Delhi, India, for the award of UGC Major Research Project {F. 30–68/2004(SR)} for financial support.