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Twist of cholesteric liquid crystal cells: stability of helical structure and anchoring energy effects

Twist of cholesteric liquid crystal cells: stability of helical structure and anchoring energy effects
Twist of cholesteric liquid crystal cells: stability of helical structure and anchoring energy effects
We consider helical configurations of a cholesteric liquid crystal (CLC) sandwiched between two substrates with homogeneous director orientation favored at both confining plates. We study the CLC twist wave number q characterizing the helical structures in relation to the free twisting number q0 which determines the equilibrium value of CLC pitch P0=2/q0. We investigate the instability mechanism underlying transitions between helical structures with different spiral half-turn numbers. Stability analysis shows that for equal finite anchoring strengths this mechanism can be dominated by in-plane director fluctuations.
In this case the metastable helical configurations are separated by the energy barriers and the transitions can be described as the director slippage through these barriers. We extend our analysis to the case of an asymmetric CLC cell in which the anchoring strengths at the two substrates are different. The asymmetry introduces two qualitatively different effects: (a) the intervals of twist wave numbers representing locally stable configurations with adjacent helix half-turn numbers are now separated by instability gaps; and (b) sufficiently large asymmetry, when the difference between azimuthal anchoring extrapolation lengths exceeds the thickness of the cell, will suppress the jumplike behavior of the twist wave number.
1539-3755
031704-[11pp]
Kiselev, A.D.
88681c32-4e74-4cc1-bfb0-61f458d47e20
Sluckin, T.J.
8dbb6b08-7034-4ae2-aa65-6b80072202f6
Kiselev, A.D.
88681c32-4e74-4cc1-bfb0-61f458d47e20
Sluckin, T.J.
8dbb6b08-7034-4ae2-aa65-6b80072202f6

Kiselev, A.D. and Sluckin, T.J. (2005) Twist of cholesteric liquid crystal cells: stability of helical structure and anchoring energy effects. Physical Review E, 71 (3), 031704-[11pp]. (doi:10.1103/PhysRevE.71.031704).

Record type: Article

Abstract

We consider helical configurations of a cholesteric liquid crystal (CLC) sandwiched between two substrates with homogeneous director orientation favored at both confining plates. We study the CLC twist wave number q characterizing the helical structures in relation to the free twisting number q0 which determines the equilibrium value of CLC pitch P0=2/q0. We investigate the instability mechanism underlying transitions between helical structures with different spiral half-turn numbers. Stability analysis shows that for equal finite anchoring strengths this mechanism can be dominated by in-plane director fluctuations.
In this case the metastable helical configurations are separated by the energy barriers and the transitions can be described as the director slippage through these barriers. We extend our analysis to the case of an asymmetric CLC cell in which the anchoring strengths at the two substrates are different. The asymmetry introduces two qualitatively different effects: (a) the intervals of twist wave numbers representing locally stable configurations with adjacent helix half-turn numbers are now separated by instability gaps; and (b) sufficiently large asymmetry, when the difference between azimuthal anchoring extrapolation lengths exceeds the thickness of the cell, will suppress the jumplike behavior of the twist wave number.

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Published date: 22 March 2005

Identifiers

Local EPrints ID: 29603
URI: http://eprints.soton.ac.uk/id/eprint/29603
ISSN: 1539-3755
PURE UUID: d4a48210-92c6-452b-9fa1-57f1f257c4f2
ORCID for T.J. Sluckin: ORCID iD orcid.org/0000-0002-9163-0061

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Date deposited: 12 May 2006
Last modified: 08 Jan 2022 02:31

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Contributors

Author: A.D. Kiselev
Author: T.J. Sluckin ORCID iD

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