Orientational order parameter estimated from molecular polarizabilities – an optical study

Abstract

An optical study of N-(p-n-alkyloxybenzylidene)-p-n-butyloxyanilines, nO.O4 compounds with the alkoxy chain number n = 1, 3, 6, 7, and 10 has been carried out by measuring the refractive indices using modified spectrometer and direct measurement of birefringence employing the Newton's rings method. Further, 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 polarizabilities α _e and α ₀ are calculated using Vuk's isotropic and Neugebauer anisotropic local field models. The order parameter S is estimated by employing the molecular polarizability values determined from experimental refractive indices and density data and the polarizability anisotropy values. Further, the order parameter S is also obtained directly from the birefringence data. A comparison has been carried out among the order parameter obtained from different ways and the results are compared with the body of the data available in the literature.

Keywords:

• order parameter
• refractive index
• birefringence and nO.O4 compounds

Acknowledgements

The authors D. Madhavi Latha and V.G.K.M. Pisipati thank the management of KL University, Vaddeswaram 522 502, India for their encouragement and support. Further, V.G.K.M. Pisipati acknowledges the financial support of Department of Science and Technology through the grant no.SR/S2/CMP-0071/2008. J. Lalitha Kumari and P.V. Datta Prasad express their deep appreciation to the management of The Hindu College, Machilipatnam, India for providing computational facilities. J. Lalitha Kumari acknowledges the financial support provided by CSIR in the form of SRF through the grant no. 8/557 (01) 2010-EMR-1.