ЧАСТОТНЫЕ И ТЕМПЕРАТУРНЫЕ ЗАВИСИМОСТИ ДИЭЛЕКТРИЧЕСКОЙ ПРОНИЦАЕМОСТИ И ТАНГЕНСА УГЛА ПОТЕРЬ НЕКОТОРЫХ НЕМАТИЧЕСКИХ ЖИДКИХ КРИСТАЛЛОВ

Abstract

The substances, capable to be in a liquid crystal state show the fluidity and anisotropy of properties and, as a result of it, easily change structure under the influence of external factors. By the preliminary researches made by a polarizing and optical method, it was revealed that connections form only a nematic liquid crystal phase. In work modern ideas of processes of formation of electric polarization, anisotropy in liquid crystals are studied. Depending on a temperature range in the studied samples dipole-group and dipole-segmental polarization may occur. Types (α and β) of the relaxation processes, lying on the basis of a method of dielectric spectroscopy are considered. The dielectric spectroscopy is one of the most effective methods of studying of molecular structure and intermolecular interaction in liquid crystal, polar substances. Modern methods of measurements and theories of permittivity and losses allow to connect in some cases their dependence on temperature and frequency of electric field with a structure, for example loudspeakers of molecules of liquid crystals. The technique of measurement of dielectric losses and permittivity of materials is described at various temperatures, frequencies and preparation of samples for measurements. Electric properties of liquid crystals at various temperatures are very important at creation of new technologies. Results of a experimental study of temperature dependence of dielectric parameters of three, earlier low-studied, connections in the temperature interval covering nematic and isotropic (near transition are presented to nematic) phases. The sign of dielectric anisotropy of a mesophase is defined by the magnitude and the direction of the molecular dipolar moment, anisotropy of polarizability, degree of orderliness of molecules and also a structure of supramolecular structures.