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Title: Effect of surface viscosity, anchoring energy, and cell gap on the response time of nematic liquid crystals

Abstract

An analytical expression for the relaxation time of a nematic liquid crystal is obtained for the first time by considering the influence of surface viscosity, anchoring energy strength and cell gap, validated numerically by using the so-called relaxation method. This general equation for the molecular response time (τ{sub 0}) was derived for a vertical aligned cell and by solving an eigenvalue equation coming from the usual balance of torque equation in the Derzhanskii and Petrov formulation, recovering the usual equations in the appropriate limit. The results show that τ∼d{sup b}, where b=2 is observed only for strongly anchored cells, while for moderate to weak anchored cells, the exponent lies between 1 and 2, depending on both, surface viscosity and anchoring strength. We found that the surface viscosity is important when calculating the response time, specially for thin cells, critical for liquid crystal devices. The surface viscosity’s effect on the optical response time with pretilt is also explored. Our results bring new insights about the role of surface viscosity and its effects in applied physics. - Highlights: • The relaxation of nematic liquid crystals is calculated by taking the surface viscosity into account. • An analytical expression for the relaxation timemore » depending on surface viscosity, anchoring strength and cell gap is obtained. • The results are numerically verified. • Surface viscosity is crucial for thin and weak anchored cells. • The effect on optical time and pretilt angle is also studied.« less

Authors:
 [1];  [2]; ;  [1];  [1];  [3]
  1. Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo 5790, 87020 - 900 Maringá –PR (Brazil)
  2. Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH 44242 (United States)
  3. (Brazil)
Publication Date:
OSTI Identifier:
22314828
Resource Type:
Journal Article
Resource Relation:
Journal Name: Annals of Physics (New York); Journal Volume: 346; Journal Issue: Complete; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANALYTICAL SOLUTION; EIGENVALUES; LIQUID CRYSTALS; RELAXATION TIME; SURFACES; TIME DEPENDENCE; TORQUE; VISCOSITY

Citation Formats

Souza, R.F. de, Yang, D.-Ke, Lenzi, E.K., Evangelista, L.R., Zola, R.S., E-mail: rzola@utfpr.edu.br, and Universidade Tecnologica Federal do Paraná, Rua Marcilio Dias 635, 86812-460 Apucarana, Paraná. Effect of surface viscosity, anchoring energy, and cell gap on the response time of nematic liquid crystals. United States: N. p., 2014. Web. doi:10.1016/J.AOP.2014.04.001.
Souza, R.F. de, Yang, D.-Ke, Lenzi, E.K., Evangelista, L.R., Zola, R.S., E-mail: rzola@utfpr.edu.br, & Universidade Tecnologica Federal do Paraná, Rua Marcilio Dias 635, 86812-460 Apucarana, Paraná. Effect of surface viscosity, anchoring energy, and cell gap on the response time of nematic liquid crystals. United States. doi:10.1016/J.AOP.2014.04.001.
Souza, R.F. de, Yang, D.-Ke, Lenzi, E.K., Evangelista, L.R., Zola, R.S., E-mail: rzola@utfpr.edu.br, and Universidade Tecnologica Federal do Paraná, Rua Marcilio Dias 635, 86812-460 Apucarana, Paraná. Tue . "Effect of surface viscosity, anchoring energy, and cell gap on the response time of nematic liquid crystals". United States. doi:10.1016/J.AOP.2014.04.001.
@article{osti_22314828,
title = {Effect of surface viscosity, anchoring energy, and cell gap on the response time of nematic liquid crystals},
author = {Souza, R.F. de and Yang, D.-Ke and Lenzi, E.K. and Evangelista, L.R. and Zola, R.S., E-mail: rzola@utfpr.edu.br and Universidade Tecnologica Federal do Paraná, Rua Marcilio Dias 635, 86812-460 Apucarana, Paraná},
abstractNote = {An analytical expression for the relaxation time of a nematic liquid crystal is obtained for the first time by considering the influence of surface viscosity, anchoring energy strength and cell gap, validated numerically by using the so-called relaxation method. This general equation for the molecular response time (τ{sub 0}) was derived for a vertical aligned cell and by solving an eigenvalue equation coming from the usual balance of torque equation in the Derzhanskii and Petrov formulation, recovering the usual equations in the appropriate limit. The results show that τ∼d{sup b}, where b=2 is observed only for strongly anchored cells, while for moderate to weak anchored cells, the exponent lies between 1 and 2, depending on both, surface viscosity and anchoring strength. We found that the surface viscosity is important when calculating the response time, specially for thin cells, critical for liquid crystal devices. The surface viscosity’s effect on the optical response time with pretilt is also explored. Our results bring new insights about the role of surface viscosity and its effects in applied physics. - Highlights: • The relaxation of nematic liquid crystals is calculated by taking the surface viscosity into account. • An analytical expression for the relaxation time depending on surface viscosity, anchoring strength and cell gap is obtained. • The results are numerically verified. • Surface viscosity is crucial for thin and weak anchored cells. • The effect on optical time and pretilt angle is also studied.},
doi = {10.1016/J.AOP.2014.04.001},
journal = {Annals of Physics (New York)},
number = Complete,
volume = 346,
place = {United States},
year = {Tue Jul 15 00:00:00 EDT 2014},
month = {Tue Jul 15 00:00:00 EDT 2014}
}