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

Sadigh, M. Khadem; Naziri, Pouriya; Zakerhamidi, M.S.; Ranjkesh, Amid; Yoon, Tae–Hoon

doi:10.1016/j.ijleo.2021.166354

Cited by 8 publications

(4 citation statements)

References 23 publications

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“…Additionally, the chiral core of most chiral materials is sensitive to temperature changes and increasing or decreasing the temperature can lead to an increase or decrease in the cholesteric pitch. For example, as previously shown [16], it was found that the chiral dopant S811 is susceptible to temperature changes. As the temperature fluctuates, the reflection color of the sample rapidly changes, indicating a shift in the cholesteric pitch and, consequently, a change in the wavelength of the central Bragg reflection for this material.…”

Section: Validation Of the Four-parameter Modelsupporting

confidence: 53%

“…The reflection bandwidth in these materials typically falls within the range of 50 to 100 nm and is influenced by the birefringence of the LC's and the chirality of the chiral material. NLCs acting as a host medium for chiral dopants are thermotropic and highly sensitive to temperature changes [15,16]; this temperature sensitivity of nematics is reflected in a change in LC birefringence, which, in turn, results in a variation in the reflection bandwidth in cholesterics [17,18]. The temperature response of CLCs serves as the foundation for constructing thermal sensors, low-power smart windows, smart labels, and temperature-sensitive single-layer films [19].…”

Section: Introductionmentioning

confidence: 99%

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Effect of different surface alignment layers and temperature changes on bandwidth of Bragg reflection in chiral nematic liquid crystal

Khalil Sarbaz,

Zakerhamidi,

Rezaei

et al. 2024

Phys. Scr.

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In recent years, the practical properties of cholesteric liquid crystals (CLCs) have been widely studied due to their unique feature of selective Bragg reflection. In this study, we investigated the following aspects: i) the effect of surface alignment using polyvinyl alcohol, polyamide, and polyimide as covering substrate, ii) the impact of temperature changes on the reflection bandwidth and, consequently, variations in the cholesteric pitch. Furthermore, we extended Li's four-parameter model to the cholesteric environment using Haller's assumption and Vuk's equations for nematic liquid crystals (NLCs) and Fergason's theory for CLCs. The fit of the experimental data with this model demonstrated an excellent agreement. The experimental data revealed that the S5011 chiral dopant, with left-handedness, used in the NLC environment of the host, exhibits a significant helical twist power (HTP). This leads to the narrowing of the reflection band width with increasing temperature, without causing a noticeable change in the wavelength of the central reflection. This feature highlights the high potential of these types of chiral materials as thermally stable materials for creating selective-reflective optical filters that remain stable with temperature changes, particularly away from the cholesteric to isotropic transition point.

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Section: Validation Of the Four-parameter Modelsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Effect of different surface alignment layers and temperature changes on bandwidth of Bragg reflection in chiral nematic liquid crystal

Khalil Sarbaz,

Zakerhamidi,

Rezaei

et al. 2024

Phys. Scr.

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show abstract

“…The reflection bands of the filters associated with the helical pitch, order parameter, and refractive indices are related to temperature due to the thermodynamic behavior of the LC molecules [65][66][67]. The temperature-dependent characteristics of the LC filters cover the central wavelength and Bragg reflection bandwidth.…”

Section: Temperature Variationmentioning

confidence: 99%

Optical Filters Based on Cholesteric, Blue and Sphere Mesophases

Sun

2022

Polymers

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An optical filter is one of the indispensable devices in massive and high-speed communication, optical signal processing, and display. Twist-structure liquid crystals, cholesteric liquid crystals, blue-phase liquid crystals, and sphere-phase liquid crystals show potential application in optical filters originating from the periodic nanostructures. Wavelength and bandwidth tuning can be controlled via temperature, electric fields, light, angle, spatial control, and templating technology. In this review, we discuss the recent developments of twist-structure liquid crystal filters.

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“…The crosslinked polymer obtained from prepolymer is used to stabilize/lock the oriented liquid crystal molecules and to reduce the switching time and driving voltage [5,6]. In addition, the polymer networks in PSBCLC have a significant effect on the transmittance, response time, absorbance, and dielectric properties of the films [7][8][9]. Therefore, the PSBCLC has received extensive attention, especially in the field of bistable cholesteric liquid crystal reflective displays [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films

Zhao

Lang

et al. 2023

Molecules

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Brightening polymer-stabilized bistable cholesteric liquid crystal (PSBCLC) films with doped fluorescent dyes were prepared using the polymerization-induced phase separation (PIPS) method. The transmittance performance behavior of these films in both states (focal conic and planar) and absorbance change in multiple dye concentrations were studied using a UV/VIS/NIR spectrophotometer. The change occurring in dye dispersion morphology with different concentrations was obtained by means of the polarizing optical microscope. The maximum fluorescence intensity of different dye-doped PSBCLC films was measured using a fluorescence spectrophotometer. Moreover, the contrast ratios and driving voltages of these films were calculated and recorded to demonstrate film performance. Finally, the optimal concentration of dye-doped PSBCLC films with a high contrast ratio and a relatively low drive voltage was found. This is expected to have great potential applications in cholesteric liquid crystal reflective displays.

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

Cited by 8 publications

References 23 publications

Effect of different surface alignment layers and temperature changes on bandwidth of Bragg reflection in chiral nematic liquid crystal

Effect of different surface alignment layers and temperature changes on bandwidth of Bragg reflection in chiral nematic liquid crystal

Optical Filters Based on Cholesteric, Blue and Sphere Mesophases

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films

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