Double Hydrogen Bonded Liquid Crystals: A Study of Light Modulation and Field Induced Transition (FiT)

Abstract

A novel series of double hydrogen bonded liquid crystals have been isolated. Hydrogen bond was formed between non mesogen ingredient succinic acid and mesogenic p-n alkoxy benzoic acids. Phase diagram was constructed from the transition temperatures obtained by differential scanning colorimetry (DSC) and polarizing optical microscopic (POM) studies. Thermal and electrical properties exhibited by succinic acid and nonyloxy benzoic acid (SA + 9BA) were discussed. Interesting feature of the present investigation was the observation of a field-induced transition (FiT) in SA + 9BA hydrogen bonded complex. Three threshold field values are noticed which gives rise to two new phases (E₁ and E₂) induced by external bias voltage and on further enhancement of the bias voltage the mesogen behaves like an optical shutter, thus this hydrogen bonded complex mesogen acts as an effective light modulator. It was noticed that FiT was reversible, in the sense that when applied filed was removed, the original texture was restored, theoretical modeling and experimental results were presented.

Keywords:

• Field induced transition
• hydrogen bonded liquid crystal
• light modulator
• SA + nBA

Acknowledgments

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