Dielectric response of cyanobiphenyl in the low frequency region

Dielectric measurement of liquid crystal materials with the cyanobiphenyl group, in different phases, are described. Measurements were carried out from 10(-4) Hz to 10(4) Hz. In both isotropic and nematic phases a linear increase of DeltaC ' = C ' - C-infinity and C " with decreasing frequency is observed at f less than or equal to 0.1 Hz. C ' and C " represent the complex capacitance, C, is the capacitance at high f. Below 0.1 Hz such behavior is not significant in the area where saturation is noticed. A similar dependence of solid and smectic phases is obtained, but all plots are shifted towards the low frequencies range. Linear dopes of log DeltaC ' and log C " vs. log f have been determined in order to evaluate fractal exponents of the dispersion laws. A very weak temperature dependence of these exponents has been noticed. The frequency of maximum loss tangent depends clearly on the temperature. This maximum shifts to higher frequencies with an increase in temperature. Results obtained have been compared with theoretical predictions of the literature models by numerical adjustment of the data.