Skip to content
BY-NC-ND 3.0 license Open Access Published by De Gruyter January 1, 2011

Analysis of deformations of flexoelectric homeotropic liquid crystal layers with various anchoring strengths

  • M. Buczkowska EMAIL logo and G. Derfel
From the journal Opto-Electronics Review

Abstract

Deformations of homeotropic layers of nematic liquid crystal possessing flexoelectric properties and subjected to external dc voltage were studied numerically. The influence of the anchoring strengthWwas investigated. The calculations were performed for two types of layers, one with positive dielectric anisotropy and positive sum of flexoelectric coefficients and the other with opposite signs of these parameters. Strongly blocking electrodes were assumed. The threshold voltages for deformations were computed for several anchoring strength values and for low, moderate, and high ion contents. The director distributions were also determined. They were influenced by joined effects of anchoring strength and space charge of ions. For increasing ion contents and increasing anchoring strength, remarkable change of deformation character was noticed. In the case of negative dielectric and flexoelectric parameters, the threshold was nearly proportional to W for low anchoring strength and saturated at some high value of W. In the case of positive dielectric and flexoelectric parameters, the threshold voltage increased strongly with W. In the range of enhanced ion concentrations, the deformation arose in two voltage ranges. The increasing anchoring strength damped the deformations in the whole layer, however, this effect was minor at high ion content.

[1] R.B. Meyer, “Piezoelectric effects in liquid crystals”, Phys. Rev. Lett. 22, 918–921 (1969). http://dx.doi.org/10.1103/PhysRevLett.22.91810.1103/PhysRevLett.22.918Search in Google Scholar

[2] J.C. Jones, E.L. Wood, G.P. Bryan-Brown, and V.C. Hui, “Novel configuration of the zenithal bistable nematic liquid crystal device”, SID 98 Digest, 858 (1998). 10.1889/1.1833899Search in Google Scholar

[3] J. Harden, B. Mbanga, N. Éber, K. Fodor-Csorba, S. Sprunt, J.T. Gleeson, and A. Jákli, “Giant flexoelectricity of bent-core nematic liquid crystals”, Phys. Rev. Lett. 97, 157802 (2006). http://dx.doi.org/10.1103/PhysRevLett.97.15780210.1103/PhysRevLett.97.157802Search in Google Scholar PubMed

[4] A. Derzhanski, A.G. Petrov, and M.D. Mitov, “One-dimensional dielectric-flexoelectric deformations in nematic layers”, J. Phys.-Paris 39, 273 (1978). http://dx.doi.org/10.1051/jphys:0197800390302730010.1051/jphys:01978003903027300Search in Google Scholar

[5] S. Naemura and A. Sawada, “Ion generation in liquid crystals under electric field”, Mol. Cryst. Liq. Cryst. 346, 155–168 (2000). http://dx.doi.org/10.1080/1058725000802387510.1080/10587250008023875Search in Google Scholar

[6] G. Derfel and M. Buczkowska, “Flexoelectric deformations of homeotropic nematic layers in the presence of ionic conductivity”, Liq. Cryst. 32, 1183–1190 (2005). http://dx.doi.org/10.1080/0267829050028440510.1080/02678290500284405Search in Google Scholar

[7] M. Buczkowska and G. Derfel, “Influence of ionic transport on deformations of homeotropic nematic layers with positive flexoelectric coefficients”, Liq. Cryst. 32, 1285–1293 (2005). http://dx.doi.org/10.1080/0267829050030322110.1080/02678290500303221Search in Google Scholar

[8] G. Derfel and M. Buczkowska, “Threshold voltage for purely flexoelectric deformations of conducting homeotropic nematic layers”, Liq. Cryst. 34, 113–125 (2007). http://dx.doi.org/10.1080/0267829060106154610.1080/02678290601061546Search in Google Scholar

[9] M. Buczkowska and G. Derfel, “Role of ions mobility in flexoelectric deformations of conducting homeotropic nematic layers”, Sci. Bull. Tech. Univ. Lódź, Physics 29, 5–24 (2008). Search in Google Scholar

[10] A. Rapini and M. Papoular, “Distorsion d’une lamelle nématique sous champ magnétique conditions d’ancrage aux parois”, J. Phys. Colloq. 30, C4-54–C4-56 (1969). (in French) http://dx.doi.org/10.1051/jphyscol:196941310.1051/jphyscol:1969413Search in Google Scholar

[11] G. Briere, F. Gaspard, and R. Herino, “Cinetique de dissociation et relaxation de conduction ionique en phase liquide”, J. Chim. Phys. 68, 845 (1971). (in French) Search in Google Scholar

[12] H. de Vleeschouwer, A. Verschueren, F. Bougriona, R. Van Asselt, E. Alexander, S. Vermael, K. Neyts, and H. Pauwels, “Long-term ion transport in nematic liquid crystal dislays”, Jpn. J. Appl. Phys. 40, 3272–3276 (2001). http://dx.doi.org/10.1143/JJAP.40.327210.1143/JJAP.40.3272Search in Google Scholar

[13] G. Derfel and A. Lipiñski, “Charge carrier mobility measurements in nematic liquid crystals”, Mol. Cryst. Liq. Cryst. 55, 89–99 (1979). http://dx.doi.org/10.1080/0026894790806979310.1080/00268947908069793Search in Google Scholar

[14] M.Y. Jin and J.J. Kim, “Low-frequency dielectric relaxations of a nonchiral liquid crystal, 8CB”, J. Phys. Condens. Matter 13, 4435–4446 (2001). http://dx.doi.org/10.1088/0953-8984/13/20/30510.1088/0953-8984/13/20/305Search in Google Scholar

[15] G. Derfel, “Numerical study of ionic current in dielectric liquid layer subjected to ac voltage”, J. Mol. Liq. 144, 59–64 (2009). http://dx.doi.org/10.1016/j.molliq.2008.10.00710.1016/j.molliq.2008.10.007Search in Google Scholar

[16] D. Oliveiro, L.R. Evangelista, and G. Barbero, “External electric-field effect on nematic anchoring energy”, Phys. Rev. E65, 031721 (2002). 10.1103/PhysRevE.65.031721Search in Google Scholar PubMed

Published Online: 2011-1-1
Published in Print: 2011-3-1

© 2011 SEP, Warsaw

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Downloaded on 29.3.2024 from https://www.degruyter.com/document/doi/10.2478/s11772-010-0065-0/html
Scroll to top button