The analysis of phase transition temperatures of SmA liquid crystal by dielectric characterization

Abstract

Due to determining true phase transition temperatures for technological device applications of liquid crystals becomes important. The differential scanning calorimetry (DSC) technique and polarizing microscope (PM) measurement methods are frequently used methods for better understanding of the phase transition temperatures in LCs. We have also researched the dielectric parameters of the liquid crystal in detail. In this study, as an alternative method, phase transition temperatures and dielectric parameters of liquid crystal which exhibits enantiotropic SmA mesophase have been analyzed by means of dielectric spectroscopy measurements. The dielectric parameters of liquid crystal have been calculated by the capacitance method via Impedance Analyzer within the frequency range of 100Hz-10MHz. In order to analyze phase transition temperatures of the LC, the temperature dependences of the real and imaginary parts of the dielectric constant of LC have been calculated. In this way, the influence of temperatures on the dielectric properties of LC and how the dielectric properties change depending on the LC phase within the temperature interval of 25-118 degrees C have been revealed. The transition temperatures of LC have been verified by the dielectric measurements by drawing graphics in three dimensions. Dielectric relaxation mechanism of LC has been analyzed by Cole-Cole curves. These curves have been exhibited semicircle and straight line. Vertical lines in Cole-Cole plot is accepted as a super-capacitive behavior.