Low frequency dielectric spectroscopy of two room temperature chiral liquid crystal mixtures

Abstract

Dielectric spectroscopy of two room temperature chiral liquid crystal mixtures (W-96 and W-97) have been carried out in the frequency range of 100 mHz–10 MHz. Low frequency dielectric relaxation modes corresponding to collective behavior of molecules (Goldstone- and soft-modes) in the SmC* phase have been found to be masked by the ionic conductance. Two slow modes of dielectric relaxation due to the ionic conductance have been detected (below 15 Hz) in planar-aligned samples. It has been observed that the effect of ionic conductance decreases with the number of thermal annealing cycles on the materials. With large number of thermal annealing cycles it has been possible to wipe out the effects of ionic conductance and then to detect other weak modes of dielectric relaxation which are otherwise masked.

Keywords:

• Chiral liquid crystal mixtures
• Dielectric spectroscopy
• Ionic conduction
• SmC* phase

Acknowledgments

We thank University Grants Commission (UGC), New Delhi for financial assistance under major research project No.10-81/2001. One of us (MBP) thanks UGC especially for a research fellowship under the project.