Study of Molecular Polarizabilities and Orientational Order Parameter in the Nematic Phase of 6.O12O.6 and 7.O12O.7

Abstract

As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an optical study of two nematogenic compounds of this series viz., 6.O12O.6 and 7.O12O.7 by carrying out the measurement of extraordinary and ordinary refractive indices using modified spectrometer. The molecular polarizability anisotropies are evaluated using Lippincott δ-function model, the molecular vibration method, Haller’s extrapolation method and scaling factor method. The molecular polrizabilities, α<sub>e</sub> and α<sub>o</sub> are calculated using Vuks’ isotropic field model and Neugebauer’s anisotropic field model. The orientational order parameter, S, is estimated by using the molecular polarizability values calculated from refractive index and denstity data as well as polarizability anisotropy values calculated as a function of temperature in the nematic phase of both of the dimers. These values are discussed with reference to the order parameter values obtained directly from the optical birefringence, Δn, data without assuming any internal field. A comparison of the order parameter values from all of these methods was carried out in the light of available literature data

Molecular spectroscopy and adverse optical properties of N-(p-hexyloxy-benzylidene)–p-toluidine (HBT) liquid crystal molecule studied by DFT methodology

“…The nematic phase exhibits long-range orientational order but no positional order of the molecule [4]. The impact of the external electric field on liquid crystal can be studied by analyzing the polarizability of the molecule [5,6]. In liquid crystals, the molecular polarizability and its anisotropy are important inherent molecular properties because the intermolecular interaction energies depend on them [7].…”

Polarizability study of nematic liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) and its nitrogen derivatives

“…Depending on the polarizability of a material, an applied electric field causes its polarization so that material can be used for a desired purpose. In liquid crystals, the molecular polarizability and its anisotropy are important inherent molecular properties because the intermolecular interaction energies depend on them [7].…”