Calculation of Optical Parameters of Liquid Crystals

Abstract

Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.

Study of optical parameters of two fluorinated isothiocyanato nematic liquid crystals exhibiting high birefringence

“…According to Haller's extrapolation me− thod, the order parameter of a LC can be approximated as [8] …”

“…In the second approach, the orientational order parameter S is calculated by using Vuks hypothesis [31] and is given as [8,19] …”

“…An NCS group placed on the terminal position of a molecule with a cyclohexylbiphenyl or cyclohexylethyl core provides strong mesogenic stability [4]. The refractive indices and birefringence of a liquid crystal, both are dependent on the molecular structure, wavelength and temperature [6][7][8]. The effect of temperature on the refractive indices and birefringence is critically important for display devices.…”

“…The effect of temperature on the refractive indices and birefringence is critically important for display devices. In order to establish a relationship of the temperature dependence of LC refractive indices, various theoretical models [6][7][8][9], as well as several experimental techniques [10][11][12][13][14] have been developed. From the study of refractive indices of liquid crystals, it is possible to obtain information on anisotropy of the light waves traversing through them [15].…”

“…The second procedure employed for the determination of order parameter is the modified Vuks method [8,19] using Haller's extrapolation [29]. In this method the well− −known Vuks relation [28] is used.…”