Influence of molecular weight on helical twisting power of oligomer chiral dopants

Wang, Xiao; He, Jialin; Wei, Qunmei; Zhang, Yang; Liu, Yu; Zhang, Zhen; Zhao, Wei; Zhou, Guofu

doi:10.1016/j.molliq.2021.116816

Cited by 5 publications

(4 citation statements)

References 33 publications

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“…The polymerization of mesogenic host (molecules 2 and 3 ) and the leaving of small molecular LC 6 result in a different LC host environment. The polymerization of chiral dopant 1 will decrease its HTP value, , while the leaving of nonpolymerizable chiral dopant 4 effectively increases the right-handed twisting effect. All these phenomena together determine the center wavelength the R-CPL reflection (Figure S4).…”

Section: Resultsmentioning

confidence: 99%

“…Inspired by the nature, scientists have been able to conceptualize versatile photonic architectures to provide appealing aesthetics and distinctive optical functions. ,− Tremendous efforts have been paid to engineer CLC materials or, more specifically, to control the helical organization of liquid crystal (LC) directors on the molecular scale. For instance, light-addressable or thermal-responsive chiral dopants allow tuning of the reflection wavelength. ,− Manipulation of the helical pitch direction or distribution provides an accessible route to realize beam steering, light diffraction, scattering, or broadband reflection. ,− Coupling helical structures of the opposite handedness can achieve hyper-reflectivity, defined as the ability to reflect both left- and right-handed circularly polarized light (L-CPL and R-CPL). − In cross-linked CLC polymers, the distortion of helical structure generates polarization-dependent pseudo-Bragg reflectors and hyper-reflectivity. − …”

Section: Introductionmentioning

confidence: 99%

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Facile Stratification-Enabled Emergent Hyper-Reflectivity in Cholesteric Liquid Crystals

Wei

Yang

et al. 2022

ACS Appl. Mater. Interfaces

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Cholesteric liquid crystals (CLCs) are chiral photonic materials with selective reflection in terms of wavelength and polarization. Helix engineering is often required in order to produce desired properties for CLC materials to be employed for beam steering, light diffraction, scattering, and adaptive or broadband reflection. Here, we demonstrate a novel photopolymerization-enforced stratification (PES)-based strategy to realize helix engineering in a chiral CLC system with initially one handedness of molecular rotation throughout the layer. PES plays a crucial role in driving the chiral dopant bundle consisting of two chiral dopants of opposite handedness to spontaneously phase separate and create a CLC bilayer structure that reflects left-and right-handed circularly polarized light (CPL). The initially hidden chiral information therefore becomes explicit, and hyper-reflectivity, i.e., reflecting both left-and right-handed CPL, successfully emerges from the designed CLC mixture. The PES mechanism can be applied to structure a wide range of liquid crystal (LC) and polymer materials. Moreover, the engineering strategy enables facile programming of the center wavelength of hyper-reflection, patterning, and incorporating stimuli-responsiveness in the optical device. Hence, the engineered hyper-reflective CLCs offer great promise for future applications, such as digital displays, lasing, optical storage, and smart windows.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Facile Stratification-Enabled Emergent Hyper-Reflectivity in Cholesteric Liquid Crystals

Wei

Yang

et al. 2022

ACS Appl. Mater. Interfaces

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“…When the pitch matches with the wavelength of light, a strong selective reflection occurs. According to the principle of the Bragg reflection, the central wavelength λ o and bandwidth Δ λ of the CLC reflection band can be represented as λ o = 〈 n 〉 p and Δ λ = Δ n · p , 29 where 〈 n 〉 and Δ n denote the average refractive index (〈 n 〉 = ( n e + n o )/2) and birefringence (Δ n = n e − n o ) of the CLC and p = 1/( βc ) is the helical pitch, 30 c is the concentration of the chiral dopant, and β is the helical twisting power.…”

Section: Methodsmentioning

confidence: 99%

A three-state label programmed using a three-color microsphere of structural, fluorescent and dye colors

Qu¹,

Li²,

Zhao³

et al. 2023

J. Mater. Chem. C

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“…When the pitch matches the wavelength of light, a strong selective reflection occurs. According to the principle of the Bragg reflection, the central wavelength λ o and bandwidth Δ λ of the CNLC reflection band can be represented as λ o = < n > p and Δ λ = Δ n ∙ p , 23 where < n > and Δ n denote the average refractive index (< n > = ( n e + n o )/2) and birefringence (Δ n = n e − n o ) of the CNLC, and p = 1/( βc ) is the helical pitch, 24 c is the concentration of the chiral dopant, and β is the helical twisting power.…”

Section: Methodsmentioning

confidence: 99%

Excellent ultraviolet‐blocking properties of chiral nematic liquid crystals

Wang

Zhang

et al. 2023

Photochem & Photobiology

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We report the evaluation of chiral nematic liquid crystal (CNLC) in blocking ultraviolet (UV). The CNLC was coated on a calcium fluoride substrate to measure the spectral transmittance, which was measured to detect the UV‐blocking effect of CNLC. The results show that CNLC could reduce UVB (290–320 nm) by 99.9% and UVA (320–400 nm) by 95.6%. The barrier effect of cake‐shaped semi‐solidified CNLC microspheres was further investigated, and it was found that cake‐shaped semi‐solidified CNLC microspheres could reduce UVB by 58.2% and UVA by 34.1%. This is due to the chemical absorption property of CNLC, which has UV‐absorbing functional groups such as the benzene rings. And the physical reflection properties of CNLC could periodically reflect a certain wavelength of light. Liquid crystal (LC) is a rich set of soft materials with rod‐like structures widely existing in nature, which is harmless to the human body and environment. Therefore, using CNLC's function of blocking UV, a new sunscreen can be developed.

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Influence of molecular weight on helical twisting power of oligomer chiral dopants

Cited by 5 publications

References 33 publications

Facile Stratification-Enabled Emergent Hyper-Reflectivity in Cholesteric Liquid Crystals

Facile Stratification-Enabled Emergent Hyper-Reflectivity in Cholesteric Liquid Crystals

A three-state label programmed using a three-color microsphere of structural, fluorescent and dye colors

Excellent ultraviolet‐blocking properties of chiral nematic liquid crystals

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