Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field

2014 ◽  
Vol 141 (18) ◽  
pp. 184903 ◽  
Author(s):  
Akihiko Matsuyama
Keyword(s):  
Liquid Crystal ◽  
External Field ◽  
Phase Diagrams ◽  
Cholesteric Liquid Crystal

Uniqueness of director configuration states for liquid crystals in the case of weak anchoring

2019 ◽  
Vol 84 (4) ◽  
pp. 748-762
Author(s):  
Carlo Greco
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
External Field ◽  
Thin Layer ◽  
Elastic Constants ◽  
Cholesteric Liquid Crystal ◽  
Stable Configuration ◽  
Director Field ◽  
Critical Thresholds ◽  
Bounding Surfaces

Abstract In a thin layer of liquid crystal the configuration of the director field depends on the interaction between the elastic properties of the material, the thickness $d$ of the layer, the boundary conditions and the external fields that may have been applied. Suitable combinations of these factors can give rise to distorted configurations (Freedericksz transitions). In this paper we assume the Oseen-Frank model for the energy and that the director field depends only on the direction orthogonal to the layer; we assume also weak anchoring conditions at the two bounding surfaces, and we mainly study the problem of uniqueness of such distorted configurations. More precisely, we first consider the nematic case in the presence of a magnetic field $\mathbf H$, and we prove the uniqueness of the stable configuration provided the magnitude of $\mathbf H$ is between two critical thresholds, simplifying some results already known in the literature, and calculating explicitly the critical thresholds. Then we study the case of a cholesteric liquid crystal without external field. In this case the director field tends to form a right-angle helicoid around a twist axis orthogonal to the layer, and we have distorted configurations (namely oblique helicoid) for suitable value of $d$. Also in this case, with suitable restrictions on the elastic constants in the Oseen-Frank energy, we find two critical thresholds for $d$, and we prove the existence of only one stable director configuration if $d$ is between them.

scholarly journals Chiral Optical Tamm States at the Interface between a Dye-Doped Cholesteric Liquid Crystal and an Anisotropic Mirror

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3255
Author(s):  
Anastasia Yu. Avdeeva ◽  
Stepan Ya. Vetrov ◽  
Rashid G. Bikbaev ◽  
Maxim V. Pyatnov ◽  
Natalya V. Rudakova ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
External Field ◽  
Structural Parameters ◽  
Cholesteric Liquid Crystal ◽  
Chiral Medium ◽  
Dye Molecules ◽  
Field Control ◽  
Tamm State ◽  
The Media ◽  
Field Localization

The resonant splitting of optical Tamm state numerically is demonstrated. The Tamm state is localized at the interface between a resonant chiral medium and a polarization-preserving anisotropic mirror. The chiral medium is considered as a cholesteric liquid crystal doped with resonant dye molecules. The article shows that the splitting occurs when dye resonance frequency coincides with the frequency of the Tamm state. In this case the reflectance, transmittance, and absorptance spectra show two distinct Tamm modes. For both modes, the field localization is at the interface between the media. The external field control of configurable optical and structural parameters paves the way for use in tunable chiral microlaser.

Dispersion of proton spin-lattice relaxation in a cholesteric liquid crystal

1983 ◽  
Vol 44 (10) ◽  
pp. 1179-1184 ◽  
Author(s):  
M. Vilfan ◽  
R. Blinc ◽  
J. Dolinšek ◽  
M. Ipavec ◽  
G. Lahajnar ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

scholarly journals Flow-assisted self-healing of the helical structure in a cholesteric liquid crystal

2021 ◽  
Vol 155 (5) ◽  
pp. 054903
Author(s):  
Jan-Christoph Eichler ◽  
Robert A. Skutnik ◽  
Marco G. Mazza ◽  
Martin Schoen
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Helical Structure ◽  
Self Healing

scholarly journals The temperature dependence of the helical pitch in a cholesteric liquid crystal

2021 ◽  
pp. e1881638
Author(s):  
Robert A. Skutnik ◽  
Jan-Christoph Eichler ◽  
Marco G. Mazza ◽  
Martin Schoen
Keyword(s):  
Liquid Crystal ◽  
Temperature Dependence ◽  
Cholesteric Liquid Crystal ◽  
Helical Pitch

Electrically tunable cholesteric liquid crystal lines defects

2021 ◽  
Vol 114 ◽  
pp. 110960
Author(s):  
Lotfi Saadaoui ◽  
Ridha Hamdi
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal
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