DIELECTRIC PROPERTIES OF A 4-PENTIL-4’-CYANOBIPHENYL LIQUID CRICTAL IN A WIDE TEMPERATURE RANGE

Abstract

Aim. We study experimentally the dispersion of the permittivity of a 5CB nematic liquid crystal in a wide temperature range and numerically approximate the obtained dependences. Methodology. The longitudinal and transverse components of the complex permittivity of a 5CB liquid crystal are measured in a wide temperature range from 263 to 318 K and in the frequency range from 100 Hz to 1 MHz by the capacitive method and at a frequency of 39.25 GHz by the waveguide method. Results. The supercooled liquid crystal phase of the substance in question, which is a combination of nematic molecules and molecular associations, is found and studied. The numerical approximation of the dielectric spectra of the nematic and supercooled liquid crystal phases is performed. Research implications. It is shown that dispersion of the longitudinal and transverse components of the permittivity of a 5CB liquid crystal in the nematic phase is satisfactorily described by the Debye equations, and in the supercooled phase by the Cole-Cole equations. The relaxation times of the dipole polarization are calculated.