Synthesis and mesomorphic properties of chiral nematic liquid crystals based on cholesterol

Abstract

A new series of mesogenic compounds having a cholesteryl moiety has been synthesised by condensing p-amino benzoate of cholesterol and methoxy substituted 4-n-alkoxy cinnamoyl chlorides and their liquid crystalline properties has been studied. All the members of the series are enantiotropic and exhibit chiral nematic (N*) mesophase. The plot of transition temperatures versus number of carbon atoms in the alkoxy chain exhibits odd–even effect and falling tendency for N*–isotropic transition temperatures. The compounds exhibit oily streak textures that on slight disturbance change to the plane textures and show iridescent colours. High anisotropy, linearity and intermolecular hydrogen bonding confer rich mesomorphic properties on the system. Intermolecular hydrogen bonding arising from amide linkage can lead to supramolecular motifs.

Keywords:

• cholesteryl moiety
• cinnamates
• chiral nematic (N*) mesophases
• intermolecular H-bonding
• ester
• amide

Acknowledgements

The authors are grateful to Prof. N.D. Kulkarni, Head, Department of Chemistry, The M.S. University of Baroda, Vadodara, for taking interest in the work and providing necessary facilities. We wish to express our gratefulness to Prof. R.A. Vora, former Head, Applied Chemistry Department, Faculty of Technology and Engineering, the M.S. University of Baroda, Vadodara, for valuable suggestions and discussions. We are also thankful to Raman Research Institute, Bangalore, for providing various analyses. One of the authors (N.K.P.) is thankful to UGC, New Delhi, for financial assistance.