Dielectric Studies of 4-n-Pentylphenyl-4-Octyloxythiobenzoate

Measurements of the complex dielectric permittivity for the isotropic, nematic and smectic phases (SA and SC) of the 4-n-pentylphenyl-4-n-octyloxythiobenzoate (8S5) have been performed in the radio frequency range and at one microwave frequency of 9.38 GHz. The dielectric anisotropy of 8S5 is positive in both the radio and microwave frequency regions. However, in the smectic C phase there is a change of sign of the dielectric anisotropy which might be connected with dipole-dipole correlations. The low frequency relaxation process exhibits a Debye-type behaviour in all liquid-crystalline phases. The temperature dependence of the dielectric relaxation time will be discussed in terms of the Arrhenius law.