Dielectric behaviour of nematic phase OHMBBA at radio frequencies

Abstract

Dielectric measurements in the frequency range 0.7 to 3.0 MHz are made in the isotropic phase and in the nematic phase of OHMBBA magnetically aligned with the long molecular axis parallel to both the magnetic and rf electric fields. Measurements in the nematic phase indicate a Debyetype dispersion with a relaxation time of 7.4 × 10−8 s at 47 °C and an activation energy of 14 kcal/mol. The results can be explained by assuming the molecular rotation about a transverse axis occuring under hindering nematic potential. The dielectric permittivity (ϵ′⊥), measured with the magnetic field acting perpendicular to rf electric field, does not vary with the magnetic field intensity, which indicates that OHMBBA probably prefers homogeneous alignment with the electrodes.