Dielectric Measurements of Guest-Host Systems

Abstract

Dielectric investigations on azo dye-5CB mixtures in the nematic and isotropic phases were carried out. The addition of the dye to the liquid crystal changes the values of the dielectric constants as well as the dielectric anisotropy, however the variations of the permittivity versus temperature and frequency are of the same type for both of the dye-5CB mixtures and the pure nematic host. It was found that the dyes having - NO₂ as the end group particularly influence the dielectric properties of the liquid crystal. The height of the potential barrier which hinders the rotation of the liquid crystal molecules in the nematic state and the order parameter of the host in the presence of a dye were estimated from the relaxation times in the nematic and isotropic phases.

Key Words:

• guest-host mixtures
• azo-dyes
• dielectric permittivity
• order parameter