Dielectric relaxation processes in the nematogen 4-cyanophenyl 4-n-heptylbenzoate

Abstract

Experimental studies of the dielectric relaxation in the nematic and isotropic phases of 4-cyanophenyl 4-n-heptylbenzoate have been performed in the frequency range from 1 kHz to 1 GHz. In the nematic phase, measurements of the complex dielectric permittivity for two orientations of the director n, parallel and perpendicular to the measuring electric field E, have been carried out. It has been found that for E n, as well as in the isotropic phase, the dielectric spectra consist of two elementary domains, described by the Cole-Cole equation, whereas for E n three Cole-Cole-type domains can be distinguished. The possible molecular reorientational movements corresponding to these domains are discussed and comparison with the theoretical predictions is made.