Dielectric properties of nematic liquid crystal with impurities of supramolecular Ni-TMTAA-TCNQ complexes

Abstract

Within the temperature range 288-343 K and frequencies 10-1-10 6 Hz, the dielectric properties of planar and homeotropic oriented nematic liquid crystal 6CHBT with the impurity of 0-3 wt.% Ni-TMTAA-TCNQ molecules have been investigated. It has been shown that at the lowest frequencies, the dispersion of components of the complex dielectric permittivity in the case of a planar oriented liquid crystal is caused by oscillations of molecular dipoles within the range of angles corresponding to fluctuations of the order parameter under the action of electric field. The values of relaxation times have been estimated, and it has been shown that with the increase in the impurity concentration, the value of the relaxation time decreases. The temperature dependences of the values inverse to the relaxation time have been analyzed. It has been shown that for the middle frequency range the obtained dielectric spectra characterize the bulk properties of the samples, in particular the value of the electrical conductivity. It has been found that with increasing the molecular concentration, the activation energy for the temperature dependence of the electrical conductivity increases. This dependence for the whole range of studied temperatures correlates with the temperature dependence of the values inverse to the relaxation time. It has been shown that at the concentration of the impurity up to 1 wt.%, the conductivity of the samples both in homeotropic and planar orientations of molecules varies according to the power law of the impurity concentration. It has been estimated the value of the exponent for the concentration dependence of conductivity, and it has been shown that it is the same for various molecular orientations.