Twist of cholesteric liquid crystal cells: Stability of helical structures and anchoring energy effects

被引:35
|
作者
Kiselev, AD
Sluckin, TJ
机构
[1] Chernigov State Technol Univ, UA-14027 Chernigov, Ukraine
[2] Univ Southampton, Sch Math, Southampton SO17 1BJ, Hants, England
来源
PHYSICAL REVIEW E | 2005年 / 71卷 / 03期
关键词
D O I
10.1103/PhysRevE.71.031704
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
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 q(0) which determines the equilibrium value of CLC pitch P-0=2 pi/q(0). 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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页数:11
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