Effect of dye dispersion on the relaxation modes of smectic C* phase

Abstract

We study how the dye dispersion influences the properties of ferroelectric liquid crystal (FLC). The polarisation measurement shows the decreasing linear behaviour with the increasing concentration of dye, indicating the orientation of dye in a direction opposite to FLC molecules. Accordingly, the response time increases with increasing concentration of dye. Dielectric data clearly show the existence of two relaxation phenomena in FLC and dye–dispersed systems. The relaxation strength of the Goldstone mode, which is observed around 200 Hz, has decreased with the dispersion of dye, and the relaxation frequency of this mode shifts towards the lower frequency side, due to increase in the rotational viscosity. The second relaxation mode, observed at ∼30 KHz, arises due to the formation of domains at the surface interface. This domain mode got suppressed with the dispersion of dye into FLC.

Keywords:

• ferroelectric liquid crystal
• Goldstone mode
• dye dispersion
• spontaneous polarisation
• guest–host effect
• response time

Acknowledgements

We are grateful to Dr. R. Dhar, Allahabad University, for useful discussion and to the Department of Science and Technology (DST), New Delhi, for the financial support.