Blue-shifting tuning of the selective reflection of polymer stabilized cholesteric liquid crystals

Soft Matter ◽  
2017 ◽  
Vol 13 (35) ◽  
pp. 5842-5848 ◽  
Author(s):  
Kyung Min Lee ◽  
Vincent P. Tondiglia ◽  
Nicholas P. Godman ◽  
Claire M. Middleton ◽  
Timothy J. White
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Dielectric Anisotropy ◽  
Cholesteric Liquid Crystals ◽  
Large Magnitude ◽  
Selective Reflection ◽  
Polymer Stabilized

We report on electrically-induced, large magnitude (>300 nm), and reversible tuning of the selective reflection in polymer stabilized cholesteric liquid crystals (PSCLCs) prepared from negative dielectric anisotropy nematic liquid crystal hosts.

Large range electrically-induced reflection notch tuning in polymer stabilized cholesteric liquid crystals

2015 ◽  
Vol 3 (34) ◽  
pp. 8788-8793 ◽  
Author(s):  
Kyung Min Lee ◽  
Vincent P. Tondiglia ◽  
Taewoo Lee ◽  
Ivan I. Smalyukh ◽  
Timothy J. White
Keyword(s):  
Liquid Crystals ◽  
Direct Current ◽  
Large Range ◽  
Dielectric Anisotropy ◽  
Cholesteric Liquid Crystals ◽  
Large Magnitude ◽  
Polymer Stabilized

This communication reports large magnitude (exceeding 1500 nm) and reversible reflection notch tuning in polymer stabilized cholesteric liquid crystals (PSCLCs) formulated with negative dielectric anisotropy (−Δε) hosts upon application of a direct current (DC) field.

Enhanced reflection band broadening in polymer stabilized cholesteric liquid crystals with negative dielectric anisotropy

2018 ◽  
Vol 267 ◽  
pp. 120-126 ◽  
Author(s):  
Hossein Nemati ◽  
Shiyi Liu ◽  
Alireza Moheghi ◽  
Vincent P. Tondiglia ◽  
Kyung Min Lee ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Dielectric Anisotropy ◽  
Band Broadening ◽  
Cholesteric Liquid Crystals ◽  
Reflection Band ◽  
Polymer Stabilized

Electrically tunable infrared reflector with adjustable bandwidth broadening up to 1100 nm

2016 ◽  
Vol 4 (16) ◽  
pp. 6064-6069 ◽  
Author(s):  
Hitesh Khandelwal ◽  
Michael G. Debije ◽  
Timothy J. White ◽  
Albertus P. H. J. Schenning
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Ethylene Glycol ◽  
Cholesteric Liquid Crystals ◽  
Anisotropic Liquid ◽  
Polymer Stabilized ◽  
Bandwidth Broadening

A tunable infrared reflector has been fabricated using polymer stabilized cholesteric liquid crystals containing a negative dielectric, anisotropic liquid crystal and a long and flexible ethylene glycol twin crosslinker.

scholarly journals Electrically Induced Splitting of the Selective Reflection in Polymer Stabilized Cholesteric Liquid Crystals

2020 ◽  
Vol 8 (19) ◽  
pp. 2000914 ◽  
Author(s):  
Brian P. Radka ◽  
Brent E. King ◽  
Michael E. McConney ◽  
Timothy J. White
Keyword(s):  
Liquid Crystals ◽  
Cholesteric Liquid Crystals ◽  
Selective Reflection ◽  
Polymer Stabilized

Thermal and electrical wavelength tuning of Bragg reflection with ultraviolet light absorbers in polymer-stabilized cholesteric liquid crystals

2018 ◽  
Vol 6 (45) ◽  
pp. 12377-12385 ◽  
Author(s):  
Amid Ranjkesh ◽  
Tae-Hoon Yoon
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Ultraviolet Light ◽  
Bragg Reflection ◽  
Cholesteric Liquid Crystal ◽  
Wavelength Tuning ◽  
Cholesteric Liquid Crystals ◽  
Light Absorbers ◽  
Polymer Stabilized

A dual thermal and electrical polymer-stabilized cholesteric liquid crystal has been fabricated by using ultraviolet light absorbers. The Bragg reflection can be autonomously controlled by temperature and manually by an electric field.

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

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 746 ◽  
Author(s):  
Kyung Min Lee ◽  
Ecklin P. Crenshaw ◽  
Mariacristina Rumi ◽  
Timothy J. White ◽  
Timothy J. Bunning ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Field Strength ◽  
Polymer Network ◽  
Dielectric Anisotropy ◽  
Cholesteric Liquid Crystals ◽  
Colored State ◽  
Electro Optic ◽  
Dc Electric Field ◽  
Polymer Stabilized ◽  
Cell Thickness

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.

Temperature dependent features of polymer stabilized cholesteric liquid crystals based on selected liquid crystal characteristics

Optik ◽  
2021 ◽  
Vol 230 ◽  
pp. 166354
Author(s):  
M. Khadem Sadigh ◽  
P. Naziri ◽  
M.S. Zakerhamidi ◽  
A. Ranjkesh ◽  
Tae-Hoon Yoon
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Cholesteric Liquid Crystals ◽  
Temperature Dependent ◽  
Polymer Stabilized

scholarly journals Enhanced Bandwidth Broadening of Infrared Reflector Based on Polymer Stabilized Cholesteric Liquid Crystals with Poly(N-vinylcarbazole) Used as Alignment Layer

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2238
Author(s):  
Limin Zhang ◽  
Qiumei Nie ◽  
Xiao-Fang Jiang ◽  
Wei Zhao ◽  
Xiaowen Hu ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Cholesteric Liquid Crystal ◽  
Critical Role ◽  
Cholesteric Liquid Crystals ◽  
Smart Window ◽  
Alignment Layer ◽  
Thermal And Electrical Properties ◽  
Polymer Stabilized

Alignment layer plays a critical role on liquid crystal (LC) conformation for most LC devices. Normally, polyimide (PI) or polyvinyl alcohol (PVA), characterized by their outstanding thermal and electrical properties, have been widely applied as the alignment layer to align LC molecules. Here, we used a semi-conductive material poly(N-vinylcarbazole) (PVK) as the alignment layer to fabricate the cholesteric liquid crystal (CLC) device and the polymer-stabilized cholesteric liquid crystals (PSCLC)-based infrared (IR) reflectors. In the presence of ultraviolet (UV) irradiation, there are hole–electron pairs generated in the PVK layer, which neutralizes the impurity electrons in the LC–PVK junction, resulting in the reduction in the built-in electric field in the LC device. Therefore, the operational voltage of the CLC device switching from cholesteric texture to focal conic texture decreases from 45 V to 30 V. For the PSCLC-based IR reflectors with the PVK alignment layer, at the same applied electric field, the reflection bandwidth is enhanced from 647 to 821 nm, ranging from 685 to 1506 nm in the IR region, which makes it attractive for saving energy as a smart window.

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