Dielectric Investigations in a Room Temperature Ferroelectric Liquid Crystal

Abstract

Dielectric relaxations along with other optical and thermal properties of a room temperature ferroelectric liquid crystal (S) -1-[4`-(octyloxy carbonyl) phenyl]-4-[2-chloro-(4-benzamido acetyl) phenyl propionato]-Benzoate is reported in the low frequency range. The mesogen exhibits cholesteric, smectic A* and smectic C* phases identified by textures threaded, focal conic and broken focal conic respectively. It is interesting to note the wide thermal span of smectic C* ranging from 65 °C to -20 °C. A relaxation process in which the relaxation is suppressed by external bias voltage, named as Gold stone mode originated at around 500 Hz is investigated with respect to temperature in the entire thermal span of smectic C* phase and is analyzed by Cole-Cole plots. The relaxation frequency shifted to the lower side as the temperature is decreased indicating Arrhenius behaviour. The distribution parameter α for various relaxation processes is calculated. From the Arrhenius graph the activation energy of the smectic C* phase is elucidated. In addition, the thermal stability of three mesophases namely cholesteric, smectic A* and smectic C* is discussed. The bi-stable switching (ON and OFF states) of the mesogen are recorded. A token of evidence for memory storage is demonstrated through dielectric hysteresis data. Light filtering action in smectic C* phase is discussed.

Keywords:

• Ferroelectric liquid crystal
• Gold stone mode
• Cole-Cole plots
• bi-stable switching
• memory storage
• light filtering

Acknowledgements

The authors acknowledge the infrastructural support provided by the Bannari Amman Institute of Technology and financial support provided by SERB, New Delhi India, vide file number EMR/2017/001075.