Study of Optical Shutter in Cholesteric Phase of a Double Hydrogen-Bonded Ferroelectric Liquid Crystal with Two Chiral Carbons

Abstract

A novel series of double hydrogen-bonded liquid crystals has been isolated. A hydrogen bond was formed between a nonmesogen chiral ingredient levo tartaric acid (LTA) and mesogenic alkyl benzoic acids (nBA). Thermal and electrical properties exhibited by levo tartaric acid and alkyl benzoic acid (LTA + nBA) are discussed. An interesting feature of the present investigation is the observation of an optical shuttering action in LTA + 8BA hydrogen-bonded complex on application of a predetermined external DC bias voltage. By enhancement of the DC bias voltage the mesogen behaves like an optical shutter; thus, the hydrogen-bonded complex mesogen acts as an effective light modulator. It was noticed that this action of shuttering was reversible, in the sense that when the applied bias voltage is removed the original texture is restored. Experimental results relating to textures, helix, optical intensity profile, dielectric studies, and optical shuttering action are presented. This optical shutter property of the mesogen can be exploited for commercial and display device applications.

Keywords:

• Chemical synthesis
• dielectric properties
• differential scanning calorimetry (DSC)
• organic compounds
• phase transitions

Acknowledgment

M. L. N. Madhu Mohan acknowledges the financial support rendered by the All India Council for Technical Education (AICTE), Department of Science and Technology (DST), and Defence Research Development Organization (DRDO), New Delhi. Infrastructural support provided by the Bannari Amman Institute of Technology is gratefully acknowledged.

Notes

C = Cooling run; h = heating run.

^a Monotropic transition.

^b Merged with crystal.