Impedance spectroscopy and dielectric anisotropy-type analysis in dye-doped nematic liquid crystals having different preliminary orientations

Abstract

Reorientation tendencies of liquid crystal (LC) molecules are investigated for two different fundamental orientation configurations known as homogeneous (HG) and homeotropic (HT). Dielectric anisotropy properties of a HT sample and a HG one are investigated as a function of frequency. The dielectric anisotropy changes from the positive type to the negative type. The obtained results suggest that the samples exhibit dielectrically controlled positive dielectric anisotropy (p-type Delta epsilon) with a critical frequency transition to negative dielectric anisotropy (n-type Delta epsilon) behavior. The high-frequency relaxation process exhibits non-Debye-type behavior due to dipolar rotation around the long molecular axis. The orientation configurations (HG and HT) change the dielectric anisotropy properties of the LC in a favorable manner. (c) 2005 Elsevier B.V. All rights reserved.