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Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy

It has previously been shown that for polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, the position and bandwidth of the selective reflection notch can be controlled by a direct-current (DC) electric field. The field-induced deformation of the polymer netw...

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Autores principales: Lee, Kyung Min, Crenshaw, Ecklin P., Rumi, Mariacristina, White, Timothy J., Bunning, Timothy J., McConney, Michael E.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040647/
https://www.ncbi.nlm.nih.gov/pubmed/32041240
http://dx.doi.org/10.3390/ma13030746
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author Lee, Kyung Min
Crenshaw, Ecklin P.
Rumi, Mariacristina
White, Timothy J.
Bunning, Timothy J.
McConney, Michael E.
author_facet Lee, Kyung Min
Crenshaw, Ecklin P.
Rumi, Mariacristina
White, Timothy J.
Bunning, Timothy J.
McConney, Michael E.
author_sort Lee, Kyung Min
collection PubMed
description It has previously been shown that for polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, the position and bandwidth of the selective reflection notch can be controlled by a direct-current (DC) electric field. The field-induced deformation of the polymer network that stabilizes the devices is mediated by ionic charges trapped in or near the polymer. A unique and reversible electro-optic response is reported here for relatively thin films (≤5 μm). Increasing the DC field strength redshifts the reflection notch to longer wavelength until the reflection disappears at high DC fields. The extent of the tuning range is dependent on the cell thickness. The transition from the reflective to the clear state is due to the electrically controlled, chirped pitch across the small cell gap and not to the field-induced reorientation of the liquid crystal molecules themselves. The transition is reversible. By adjusting the DC field strength, various reflection wavelengths can be addressed from either a different reflective (colored) state at 0 V or a transparent state at a high DC field. Relatively fast responses (~50 ms rise times and ~200 ms fall times) are observed for these thin PSCLCs.
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spelling pubmed-70406472020-03-09 Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy Lee, Kyung Min Crenshaw, Ecklin P. Rumi, Mariacristina White, Timothy J. Bunning, Timothy J. McConney, Michael E. Materials (Basel) Article It has previously been shown that for polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, the position and bandwidth of the selective reflection notch can be controlled by a direct-current (DC) electric field. The field-induced deformation of the polymer network that stabilizes the devices is mediated by ionic charges trapped in or near the polymer. A unique and reversible electro-optic response is reported here for relatively thin films (≤5 μm). Increasing the DC field strength redshifts the reflection notch to longer wavelength until the reflection disappears at high DC fields. The extent of the tuning range is dependent on the cell thickness. The transition from the reflective to the clear state is due to the electrically controlled, chirped pitch across the small cell gap and not to the field-induced reorientation of the liquid crystal molecules themselves. The transition is reversible. By adjusting the DC field strength, various reflection wavelengths can be addressed from either a different reflective (colored) state at 0 V or a transparent state at a high DC field. Relatively fast responses (~50 ms rise times and ~200 ms fall times) are observed for these thin PSCLCs. MDPI 2020-02-06 /pmc/articles/PMC7040647/ /pubmed/32041240 http://dx.doi.org/10.3390/ma13030746 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Lee, Kyung Min
Crenshaw, Ecklin P.
Rumi, Mariacristina
White, Timothy J.
Bunning, Timothy J.
McConney, Michael E.
Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
title Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
title_full Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
title_fullStr Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
title_full_unstemmed Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
title_short Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy
title_sort effect of cell thickness on the electro-optic response of polymer stabilized cholesteric liquid crystals with negative dielectric anisotropy
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040647/
https://www.ncbi.nlm.nih.gov/pubmed/32041240
http://dx.doi.org/10.3390/ma13030746
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