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

• 作者: D. Bhuyan D. Madhavi Latha K. N. Singh P. Pardhasaradhi P. V. Datta Prasad Parameswara Rao Alapati V. G. K. M. Pisipati
• 来源期刊: 凝固态物理国际期刊(英文)
• 学科: 化学
• 关键词: SYMMETRIC Liquid CRYSTAL DIMERS Refractive Index Orientational Order PARAMETER MOLECULAR POLARIZABILITY
• 年，卷（期）: 2011,（4）
• 页码范围: 167-174
• 页数: 8页
• 分类号: O6

摘要

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, αe and αo 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.