Determination of anchoring energy, diamagnetic susceptibility anisotropy, and elasticity of some nematics by means of semiempirical method of self-consistent director field

J. Kędzierski; M. A. Kojdecki; Z. Raszewski; J. Zieliński; L. Lipińska

doi:10.1117/12.648167

6 December 2006 Determination of anchoring energy, diamagnetic susceptibility anisotropy, and elasticity of some nematics by means of semiempirical method of self-consistent director field

J. Kędzierski, M. A. Kojdecki, Z. Raszewski, J. Zieliński, L. Lipińska

Author Affiliations +

Proceedings Volume 6023, Tenth International Conference on Nonlinear Optics of Liquid and Photorefractive Crystals; 602305 (2006) https://doi.org/10.1117/12.648167
Event: Tenth International Conference on Nonlinear Optics of Liquid and Photorefractive Crystals, 2005, Alushta, Ukraine

Abstract

Flat-parallel cells filled with several nematic liquid crystals of both planar or homeotropic steady-state alignments were exploited to study some of their properties. To make results of investigation more reliable wedge cells of the wedge angle of order of few milliradians were used to measure threshold electric and magnetic fields for the different kinds of Freedericksz transition. Nematic liquid crystals filling wedge cells were of planar orientation enforced by the treatment of flat boundary plates. A system of interference fringes appeared in a cell placed in normally incident light between analyser and polariser crossed. In the vicinity of each fringe a cell could be considered as a flat-parallel one and hence it was equivalent to a system of flat cells of different precisely determined thickness; the same relates to any cell of slowly varying thickness and flat cover plates. The threshold electric and magnetic field magnitudes were interpreted as the eigenvalues of the boundary eigenvalue problem for the operator of the second derivative; the interaction between the nematics and the substrates was described by the Rapini-Papoular formula (i.e. weak coupling was considered) or by a polynomials. The resulting formulae were used to determine the anisotropy of diamagnetic susceptibility and the splay and bend elastic constants of a few nematic liquid crystals (PCB, 6CHBT, DE) and the polar anchoring energy coefficient, after the measured threshold fields. The improved method exploiting a self-consistent director field was applied to determine all these parameters and the coupling between the nematics and the substrates made of some polyimides. The estimates of material parameters agreed pretty well with data taken from literature.

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J. Kędzierski, M. A. Kojdecki, Z. Raszewski, J. Zieliński, and L. Lipińska "Determination of anchoring energy, diamagnetic susceptibility anisotropy, and elasticity of some nematics by means of semiempirical method of self-consistent director field", Proc. SPIE 6023, Tenth International Conference on Nonlinear Optics of Liquid and Photorefractive Crystals, 602305 (6 December 2006); https://doi.org/10.1117/12.648167

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