Dielectric Anisotropy and AC Conductivity of Bicomponent Mixtures of Liquid Crystals Cholesteryl Pelargonate and Nonyloxybenzoic Acid

Abstract

Dielectric constant (ε′) and electrical conductivity ([sgrave]) of the binary mixtures of cholesteryl pelargonate (ChP) and nonyloxybenzoic acid (NOBA) of different concentrations have been measured in the frequency range of 100 Hz to 10 MHz from room temperature to 150°C both in planar and homeotropic alignments. These mixtures do not show the dielectric dispersion upto 10 MHz. Dielectric constants parallel and perpendicular to helical axes (ε′_∥ and ε′^⊥) and the dielectric anisotropy (Δε′ = ε′_∥ - ε′^⊥) have been determined in different mesophases. Dielectric anisotropy (Δε′) of the mixtures changes sign from negative to a positive value for NOBA concentrations above 75 mole %. From the measured frequency dependent conductivity [sgrave](f), d.c. conductivity [sgrave](dc) has been obtained using the universal power law equation. Activation energy (W _a) of the d.c. conduction process has been determined in different mesophases.

Key Words:

• Liquid crystal mixture
• cholesteryl pelargonate
• nonyloxybenzoic acid
• dielectric anisotropy
• conductivity