Orientational Order Parameter-II – A Birefringence Study

Pardhasaradhi, P and Murthy, C S V S and Kumar, Lalitha J and Prasad, Datta P V and Srinivasulu, M and Pisipati, V G K M (2009) Orientational Order Parameter-II – A Birefringence Study. Molecular Crystals and Liquid Crystals, 511 (1). pp. 121-132. ISSN 1563-5287

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Different techniques are available for the estimation of order parameter in the nematic phase of liquid crystals. However, most of these methods are not applicable to Cholesteric and smectic phases and therefore, the experimental data regarding the order parameter in these phases are hardly available. Measurement results of birefringence and refractive index of liquid-crystalline N-(p-n-pentyloxybenzylidene)- p-n-pentylaniline, 5O.5, N-(p-n-pentylbenzylidene)-p-n-pentylaniline, 5.5, N-(p-n-pentylbenzylidene)-p-n-pentyloxyaniline, 5.O5, and N-(p-n-hexyloxybenzylidene)- p-n-pentyloxyaniline, 6O.O5, were presented. Using these data, the polarizability anisotropy was calculated for both Vuks and Neugebauer local field models. Polarizabilities calcula ted in this way were applied to determine Da (polarizability anisotropy in the case of perfect orientation) using either Haller’s and=or Subramhanyam’s normalization procedures. Further, the polarisability anisotropy in the perfect order was calculated theoretically using the d-function model developed by Lippincott et al. These procedures enabled the calculation of the orientation order parameter. Polarizabilities calculated using both local field models and from d-function model developed by Lippincott et al. have been compared. The values of polarizability anisotropy for both local electric field models differ significantly. No criterion is known to decide which value is correct. To avoid the determination of uncertain ai and Da values considering different local field models, a simple procedure developed by Kuczynski et al. was used for evaluation of S, based solely on birefringence measurement. This procedure gave very reasonable results.

Item Type: Article
Additional Information: Copyright # Taylor & Francis Group, LLC
Uncontrolled Keywords: birefringence; local field models; orientation order parameter; polarizability anisotropy
Subjects: Engineering > MIT Manipal > Chemistry
Depositing User: MIT Library
Date Deposited: 09 Feb 2013 07:46
Last Modified: 09 Feb 2013 07:46
URI: http://eprints.manipal.edu/id/eprint/78312

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