Molecules

Research

Jump to: Review

18 pages, 6363 KiB

Open AccessArticle

Programmable Complex Shape Changing of Polysiloxane Main-Chain Liquid Crystalline Elastomers

by Yuhe Zhang, Xiuxiu Wang, Wenlong Yang, Huixuan Yan, Xinyu Zhang, Dongxu Han, Yifan He, Chensha Li and Liguo Sun

Molecules 2023, 28(12), 4858; https://doi.org/10.3390/molecules28124858 - 20 Jun 2023

Cited by 1 | Viewed by 1602

Abstract

Liquid crystal elastomers (LCEs) are shape-morphing materials whose large and reversible shape transformations are caused by the coupling between the mobile anisotropic properties of liquid crystal (LC) units and the rubber elastic of polymer networks. Their shape-changing behaviors under certain stimuli are largely [...] Read more.

Liquid crystal elastomers (LCEs) are shape-morphing materials whose large and reversible shape transformations are caused by the coupling between the mobile anisotropic properties of liquid crystal (LC) units and the rubber elastic of polymer networks. Their shape-changing behaviors under certain stimuli are largely directed by the LC orientation; therefore, various strategies have been developed to spatially modulate the LC alignments. However, most of these methods are limited as they require complex fabrication technologies or have intrinsic limitations in applicability. To address this issue, programmable complex shape changes in some LCE types, such as polysiloxane side-chain LCEs, thiol-acrylate main-chain LCEs, etc., were achieved by using a mechanical alignment programming process coupled with two-step crosslinking. Here, we report a polysiloxane main-chain LCE with programmable 2- and 3D shape-changing abilities that were created by mechanically programming the polydomain LCE with two crosslinking steps. The resulting LCEs exhibited a reversible thermal-induced shape transformation between the initial and programmed shapes due to the two-way memory between the first and second network structures. Our findings expand on the applications of LCE materials in actuators, soft robotics, and smart structures where arbitrary and easily programmed shape morphing is needed. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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15 pages, 5194 KiB

Open AccessArticle

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

by Yuzhen Zhao, Chaonian Li, Tingting Lang, Yitian Sun, Qingbo Li, Xinli Shi, Ruijuan Yao, Huimin Zhang and Yang Zhao

Molecules 2023, 28(8), 3509; https://doi.org/10.3390/molecules28083509 - 16 Apr 2023

Cited by 3 | Viewed by 1917

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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8 pages, 4650 KiB

Open AccessArticle

Research of Liquid-Crystal Materials for a High-Performance FFS-TFT Display

by Haiguang Chen, Youran Liu, Maoxian Chen, Tianmeng Jiang, Lanying Zhang, Zhou Yang and Huai Yang

Molecules 2023, 28(2), 754; https://doi.org/10.3390/molecules28020754 - 11 Jan 2023

Cited by 12 | Viewed by 2004

Abstract

A novel liquid-crystal compound of more than 99.95% purity with high performance (such as a high clearing point, large dielectric anisotropy, high optical anisotropy, low viscosity, and large elastic constants) was designed and synthesized according to the fringe-field switching thin-film-transistor-liquid-crystal display requirements (FFS-TFT). [...] Read more.

A novel liquid-crystal compound of more than 99.95% purity with high performance (such as a high clearing point, large dielectric anisotropy, high optical anisotropy, low viscosity, and large elastic constants) was designed and synthesized according to the fringe-field switching thin-film-transistor-liquid-crystal display requirements (FFS-TFT). Then, a mixed liquid-crystal material suitable for an FFS-TFT display was developed by mixing this compound with other reported compounds, developing a product whose quality was that of the highest level of similar foreign products and which fully met the customer’s use requirements (BOE), and thus able to completely replace similar imported materials. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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10 pages, 3247 KiB

Open AccessArticle

Luminous Self-Assembled Fibers of Azopyridines and Quantum Dots Enabled by Synergy of Halogen Bond and Alkyl Chain Interactions

by Ying Pan, Lulu Xue, Yinjie Chen, Yingjie Hu, Zhicheng Sun, Lixin Mo, Luhai Li and Haifeng Yu

Molecules 2022, 27(23), 8165; https://doi.org/10.3390/molecules27238165 - 23 Nov 2022

Viewed by 1554

Abstract

Herein, a simple approach for the fabrication of luminous self-assembled fibers based on halogen-bonded azopyridine complexes and oleic acid-modified quantum dots (QDs) is reported. The QDs uniformly align on the edge of the self-assembled fibers through the formation of van der Waals force [...] Read more.

Herein, a simple approach for the fabrication of luminous self-assembled fibers based on halogen-bonded azopyridine complexes and oleic acid-modified quantum dots (QDs) is reported. The QDs uniformly align on the edge of the self-assembled fibers through the formation of van der Waals force between the alkyl chain of oleic acid on the QD surface and the alkyl chain of the halogen-bonded complexes, 15Br or 15I. Furthermore, the intermolecular interaction mechanism was elucidated by using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and density functional theory (DFT) calculations. This approach results in retention of the fluorescence properties of the QDs in the fibers. In addition, the bromine-bonded fibers can be assembled into tailored directional fibers upon evaporation of the solvent (tetrahydrofuran) when using capillaries via the capillary force. Interestingly, the mesogenic properties of the halogen-bonded complexes are preserved in the easily prepared halogen-bonded fluorescent fibers; this provides new insight into the design of functional self-assembly materials. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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11 pages, 4156 KiB

Open AccessArticle

Electro-Optical Characteristics of Polymer Dispersed Liquid Crystal Doped with MgO Nanoparticles

by Yuzhen Zhao, Jinqian Li, Yang Yu, Yang Zhao, Zhun Guo, Ruijuan Yao, Jianjing Gao, Yongming Zhang and Dong Wang

Molecules 2022, 27(21), 7265; https://doi.org/10.3390/molecules27217265 - 26 Oct 2022

Cited by 10 | Viewed by 1743

Abstract

In this paper, inorganic oxide MgO nanoparticles-doped polymer dispersed liquid crystal (PDLC) films were made from a mixture of the prepolymer, SLC1717 liquid crystal, and MgO nanoparticles by the polymerization induced phase separation (PIPS) process. To observe the effect of MgO concentration, PDLC [...] Read more.

In this paper, inorganic oxide MgO nanoparticles-doped polymer dispersed liquid crystal (PDLC) films were made from a mixture of the prepolymer, SLC1717 liquid crystal, and MgO nanoparticles by the polymerization induced phase separation (PIPS) process. To observe the effect of MgO concentration, PDLC was dispersed with 0.2, 0.4, 0.6, and 0.8 wt.% MgO. Electro-optical properties of the films have been investigated using LCD parameter meter and Scanning Electron Microscope (SEM) at room temperature. It is established that MgO nanoparticles affect the microstructure of PDLC films significantly because of the formed agglomerates of MgO nanoparticles. Results show an improvement in the electro-optical properties and a decrease in the driving voltage for doped systems with MgO nanoparticles. When the doping amount of MgO is 0.8 wt.%, the threshold voltage (V_th) is reduced to about 7.5 V. Therefore, MgO-doped PDLC is expected to become an excellent choice in the field of energy-saving. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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13 pages, 10639 KiB

Open AccessArticle

Negative Dielectric Anisotropy Liquid Crystal with Improved Photo-Stability, Anti-Flicker, and Transmittance for 8K Display Applications

by Haiguang Chen, Youran Liu, Maoxian Chen, Tianmeng Jiang, Zhou Yang and Huai Yang

Molecules 2022, 27(21), 7150; https://doi.org/10.3390/molecules27217150 - 22 Oct 2022

Cited by 6 | Viewed by 1753

Abstract

Video systems such as 8K displays can provide a strong sense of presence and reality due to their extremely high resolution and wide field of view. However, high-resolution displays generally suffer from reduced transmittance, which requires the use of liquid crystals with high [...] Read more.

Video systems such as 8K displays can provide a strong sense of presence and reality due to their extremely high resolution and wide field of view. However, high-resolution displays generally suffer from reduced transmittance, which requires the use of liquid crystals with high transmittance and high stability. In this study, negative dielectric anisotropy liquid crystal compositions with excellent photo-stability, anti-flicker capability, and high transmittance are developed, showing potential for 8K display applications. The stability of different types of negative dielectric anisotropy liquid crystal compounds is assessed under light, and the high photo-stability compounds are obtained. In addition, it is demonstrated that the flicker can be optimized from −17.6 to −47.0 by removing the compounds with a higher ion content and a larger deformation number and adding the compounds with a smaller deformation number in the negative dielectric anisotropy liquid crystal compositions. Combining with the evaluation of the factors affecting the response time, the negative dielectric anisotropy liquid crystal mixed H is designed with improved stability and flicker; thus, the response time was decreased to 9.5 ms, and the optical transmittance was 5.5% higher than that of MAT-09-1284 (for normal) and 3.1% higher than that of BY19-J01A (for 4K). Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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10 pages, 2574 KiB

Open AccessArticle

Spatial Patterning of Fluorescent Liquid Crystal Ink Based on Inkjet Printing

by Lei Zhang, Yongfeng Cui, Qi Wang, Huimin Zhou, Hao Wang, Yuzhan Li, Zhou Yang, Hui Cao, Dong Wang and Wanli He

Molecules 2022, 27(17), 5536; https://doi.org/10.3390/molecules27175536 - 28 Aug 2022

Cited by 8 | Viewed by 2188

Abstract

Fluorescent cholesteric liquid crystal materials (FCLC) with aggregation-induced emission (AIE) properties can effectively solve the contradiction between aggregation-induced quenching (ACQ) and liquid crystal self-assembly when light-emitting materials are aggregated, and they have great application value in the fields of anti-counterfeit detection and information [...] Read more.

Fluorescent cholesteric liquid crystal materials (FCLC) with aggregation-induced emission (AIE) properties can effectively solve the contradiction between aggregation-induced quenching (ACQ) and liquid crystal self-assembly when light-emitting materials are aggregated, and they have great application value in the fields of anti-counterfeit detection and information hiding. However, generating a visually appealing design, logo, or image in the application typically requires an intricate fabrication process, such as the use of prefabricated molds and photomasks, which greatly limits the practical application of FCLC materials. Herein is reported a new method for spatially patterned liquid crystal (LC) microdroplet arrays using drop-on-demand inkjet printing technology. Through rational composition design, a spatial array composed of different liquid crystal microdroplets was established, and the array contains two entirely distinct but intact patterns at the same time, which can be reversibly switched under the irradiation of UV and natural light. This study provides a new method for the integrated preparation of different component liquid crystal materials. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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13 pages, 4162 KiB

Open AccessArticle

Light-Responsive Hexagonal Assemblies of Triangular Azo Dyes

by Mina Han and Khin Moe

Molecules 2022, 27(14), 4380; https://doi.org/10.3390/molecules27144380 - 8 Jul 2022

Cited by 1 | Viewed by 1763

Abstract

The rational design of small building block molecules and understanding their molecular assemblies are of fundamental importance in creating new stimuli-responsive organic architectures with desired shapes and functions. Based on the experimental results of light-induced conformational changes of four types of triangular azo [...] Read more.

The rational design of small building block molecules and understanding their molecular assemblies are of fundamental importance in creating new stimuli-responsive organic architectures with desired shapes and functions. Based on the experimental results of light-induced conformational changes of four types of triangular azo dyes with different terminal functional groups, as well as absorption and fluorescence characteristics associated with their molecular assemblies, we report that aggregation-active emission enhancement (AIEE)-active compound (1) substituted with sterically crowded tert-butyl (t-Bu) groups showed approximately 35% light-induced molecular switching and had a strong tendency to assemble into highly stable hexagonal structures with AIEE characteristics. Their sizes were regulated from nanometer-scale hexagonal rods to micrometer-scale sticks depending on the concentration. This is in contrast to other triangular compounds with bromo (Br) and triphenylamine (TPA) substituents, which exhibited no photoisomerization and tended to form flexible fibrous structures. Moreover, non-contact exposure of the fluorescent hexagonal nanorods to ultraviolet (UV) light led to a dramatic hexagonal-to-amorphous structure transition. The resulting remarkable variations, such as in the contrast of microscopic images and fluorescence characteristics, were confirmed by various microscopic and spectroscopic measurements. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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9 pages, 2933 KiB

Open AccessCommunication

Visible Light-Driven Alkyne-Grafted Ethylene-Bridged Azobenzene Chromophores for Photothermal Utilization

by Wenyu Fang, Yiyu Feng, Jian Gao, Hui Wang, Jing Ge, Qingbin Yang and Wei Feng

Molecules 2022, 27(10), 3296; https://doi.org/10.3390/molecules27103296 - 20 May 2022

Cited by 2 | Viewed by 1891

Abstract

Molecular photoswitches are considered to be important candidates in the field of solar energy storage due to their sensitive and reversible bidirectional optical response. Nevertheless, it is still a daunting challenge to design a molecular photoswitch to improve the low solar spectrum utilization [...] Read more.

Molecular photoswitches are considered to be important candidates in the field of solar energy storage due to their sensitive and reversible bidirectional optical response. Nevertheless, it is still a daunting challenge to design a molecular photoswitch to improve the low solar spectrum utilization and quantum yields while achieving charging and discharging of heat without solvent assistance. Herein, a series of visible-light-driven ethylene-bridged azobenzene (b-Azo) chromophores with different alkyne substituents which can undergo isomerization reactions promoted in both directions by visible light are reported. Their visible light responsiveness improves their solar spectrum utilization while also having high quantum yields. In addition, as the compounds are liquids, there is no need to dissolve the compounds in order to exploit this switching. The photoisomerization of b-Azo can be adjusted by alkyne-related substituents, and hexyne-substituted b-Azo is able to store and release photothermal energy with a high density of 106.1 J·g⁻¹, and can achieve a temperature increase of 1.8 °C at a low temperature of −1 °C. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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12 pages, 3120 KiB

Open AccessArticle

Unidirectional Alignment of Surface-Grafted ZnO Nanorods in Micrometer-Thick Cells Using Low-Molecular-Weight Liquid Crystals

by Kaho Ogata, Kohsuke Matsumoto, Yoshiaki Kobayashi, Shoichi Kubo and Atsushi Shishido

Molecules 2022, 27(3), 689; https://doi.org/10.3390/molecules27030689 - 21 Jan 2022

Cited by 1 | Viewed by 2381

Abstract

Inorganic nanomaterials such as nanotubes and nanorods have attracted great attention due to their anisotropic properties. Although the alignment control of inorganic nanomaterials is key to the development of functional devices utilizing their fascinating properties, there is still difficulty in achieving uniform alignment [...] Read more.

Inorganic nanomaterials such as nanotubes and nanorods have attracted great attention due to their anisotropic properties. Although the alignment control of inorganic nanomaterials is key to the development of functional devices utilizing their fascinating properties, there is still difficulty in achieving uniform alignment over a large area with a micrometer thickness. To overcome this problem, we focused on liquid crystals (LCs) to promote the alignment of anisotropic nanomaterials, taking advantage of the cooperative motion of LCs. We present the uniform, one-dimensional alignment of ZnO nanorods along the direction of LCs in micrometer-thick cells by grafting nematic LC polymers from the nanorod surfaces to provide miscibility with the host LCs. Polarized optical microscopy and polarized UV–visible absorption spectroscopy revealed the unidirectional alignment of nematic LC polymer-grafted ZnO nanorods parallel to the nematic host LCs. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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10 pages, 3323 KiB

Open AccessArticle

An Electrically and Thermally Erasable Liquid Crystal Film Containing NIR Absorbent Carbon Nanotube

by Zongcheng Miao and Dong Wang

Molecules 2022, 27(2), 562; https://doi.org/10.3390/molecules27020562 - 17 Jan 2022

Cited by 5 | Viewed by 2068

Abstract

Carbon nanotubes (CNTs) coated by a poly(vinylpyrrolidone) (PVP) layer were doped in bistable cholesteric liquid crystal (ChLC) film to provide electric, thermal, or optical erasability controllable films. The CNT/PVP formed a compatible NIR-absorbing film that can generate heat to switch ChLC film from [...] Read more.

Carbon nanotubes (CNTs) coated by a poly(vinylpyrrolidone) (PVP) layer were doped in bistable cholesteric liquid crystal (ChLC) film to provide electric, thermal, or optical erasability controllable films. The CNT/PVP formed a compatible NIR-absorbing film that can generate heat to switch ChLC film from a planar texture to a focal conic texture. The appropriate content of CNT/PVP is provided to achieve a fast thermal response, satisfactory dispersion, and clear display brightness. The ChLC film containing CNT/PVP @ 0.8 (wt.%) saves 51% time at thermal erasing, compared to the ChLC mixture without NIR absorbent. The hybrid organic–inorganic bistable ChLC material reported here extends and offers new applications of ChLC writing tablets. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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11 pages, 3997 KiB

Open AccessArticle

High-Reflective Templated Cholesteric Liquid Crystal Filters

by Yao Gao, Yuxiang Luo and Jiangang Lu

Molecules 2021, 26(22), 6889; https://doi.org/10.3390/molecules26226889 - 15 Nov 2021

Cited by 15 | Viewed by 2844

Abstract

Cholesteric liquid crystals (CLCs) have been widely applied in optical filters due to Bragg reflection caused by their helical structure. However, the reflectivity of CLC filters is relatively low, commonly less than 50%, as the filters can only reflect light polarized circularly either [...] Read more.

Cholesteric liquid crystals (CLCs) have been widely applied in optical filters due to Bragg reflection caused by their helical structure. However, the reflectivity of CLC filters is relatively low, commonly less than 50%, as the filters can only reflect light polarized circularly either left- or right-handedly. Therefore, a high-reflective CLC filter with a single-layer template was proposed which may reflect both right- and left-handed polarized light. The CLC filters of the red, green, blue color were fabricated by the templating technology, which show good wavelength consistency. Additionally, a multi-phase liquid crystal filter with high reflectance was demonstrated by the single-layer templating technology. The templated CLC or multi-phase liquid crystal filters show great potential applications in the optical community, reflective display, and lasing. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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12 pages, 4009 KiB

Open AccessArticle

Effect of the Duty Cycle of Flower-like Silver Nanostructures Fabricated with a Lyotropic Liquid Crystal on the SERS Spectrum

by Shen Zhang, Zhihui Jiang, Yijin Liang, Yili Shen, Hongmin Mao, Huijuan Sun, Xin Zhao, Xiaoping Li, Wusheng Hu, Guoding Xu and Zhaoliang Cao

Molecules 2021, 26(21), 6522; https://doi.org/10.3390/molecules26216522 - 28 Oct 2021

Cited by 4 | Viewed by 1765

Abstract

Surface-enhanced Raman scattering (SERS) has been widely reported to improve the sensitivity of Raman spectra. Ordinarily, the laser is focused on the sample to measure the Raman spectrum. The size of the focused light spot is comparable with that of micro-nano structures, and [...] Read more.

Surface-enhanced Raman scattering (SERS) has been widely reported to improve the sensitivity of Raman spectra. Ordinarily, the laser is focused on the sample to measure the Raman spectrum. The size of the focused light spot is comparable with that of micro-nano structures, and the number of micro-nano structures contained in the light spot area (defined as duty cycle) will severely affect the spectrum intensity. In this study, flower-like silver nanostructures were fabricated with a soft lyotropic liquid crystal template in order to investigate the effect of duty cycle. They were observed under a scanning electron microscope, and their spectrum enhancement factor was computed with the obtained Raman spectrum. Then, their duty cycles were measured using a SERS substrate at different locations. A formula was derived to represent the relation between the duty cycle of the nanoflowers and the Raman spectral intensity. This work could promote the actual applications of SERS in high-sensitivity spectrum testing. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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11 pages, 2887 KiB

Open AccessArticle

Effect of Crosslinkers on Optical and Mechanical Behavior of Chiral Nematic Liquid Crystal Elastomers

by Kyosun Ku, Kyohei Hisano, Kyoko Yuasa, Tomoki Shigeyama, Norihisa Akamatsu, Atsushi Shishido and Osamu Tsutsumi

Molecules 2021, 26(20), 6193; https://doi.org/10.3390/molecules26206193 - 14 Oct 2021

Cited by 7 | Viewed by 2725

Abstract

Chiral nematic (N*) liquid crystal elastomers (LCEs) are suitable for fabricating stimuli-responsive materials. As crosslinkers considerably affect the N*LCE network, we investigated the effects of crosslinking units on the physical properties of N*LCEs. The N*LCEs were synthesized with different types of crosslinkers, and [...] Read more.

Chiral nematic (N*) liquid crystal elastomers (LCEs) are suitable for fabricating stimuli-responsive materials. As crosslinkers considerably affect the N*LCE network, we investigated the effects of crosslinking units on the physical properties of N*LCEs. The N*LCEs were synthesized with different types of crosslinkers, and the relationship between the N*LC polymeric system and the crosslinking unit was investigated. The N*LCEs emit color by selective reflection, in which the color changes in response to mechanical deformation. The LC-type crosslinker decreases the helical twisting power of the N*LCE by increasing the total molar ratio of the mesogenic compound. The N*LCE exhibits mechano-responsive color changes by coupling the N*LC orientation and the polymer network, where the N*LCEs exhibit different degrees of pitch variation depending on the crosslinker. Moreover, the LC-type crosslinker increases the Young’s modulus of N*LCEs, and the long methylene chains increase the breaking strain. An analysis of experimental results verified the effect of the crosslinkers, providing a design rationale for N*LCE materials in mechano-optical sensor applications. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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Review

Jump to: Research

38 pages, 11626 KiB

Open AccessReview

Recent Development of Tunable Optical Devices Based on Liquid

by Qi Wu, Hongxia Zhang, Dagong Jia and Tiegen Liu

Molecules 2022, 27(22), 8025; https://doi.org/10.3390/molecules27228025 - 18 Nov 2022

Cited by 12 | Viewed by 3977

Abstract

Liquid opens up a new stage of device tunability and gradually replaced solid-state devices and mechanical tuning. It optimizes the control method and improves the dynamic range of many optical devices, exhibiting several attractive features, such as rapid prototyping, miniaturization, easy integration and [...] Read more.

Liquid opens up a new stage of device tunability and gradually replaced solid-state devices and mechanical tuning. It optimizes the control method and improves the dynamic range of many optical devices, exhibiting several attractive features, such as rapid prototyping, miniaturization, easy integration and low power consumption. The advantage makes optical devices widely used in imaging, optical control, telecommunications, autopilot and lab-on-a-chip. Here, we review the tunable liquid devices, including isotropic liquid and anisotropic liquid crystal devices. Due to the unique characteristics of the two types of liquids, the tuning principles and tuning methods are distinguished and demonstrated in detail firstly and then some recent progress in this field, covering the adaptive lens, beam controller, beam filter, bending waveguide, iris, resonator and display devices. Finally, the limitations and future perspectives of the current liquid devices are discussed. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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20 pages, 7261 KiB

Open AccessReview

Research Progress of Cholesteric Liquid Crystals with Broadband Reflection

by Huimin Zhou, Hao Wang, Wanli He, Zhou Yang, Hui Cao, Dong Wang and Yuzhan Li

Molecules 2022, 27(14), 4427; https://doi.org/10.3390/molecules27144427 - 11 Jul 2022

Cited by 20 | Viewed by 4617

Abstract

Cholesteric liquid crystal (ChLC) materials with broadband reflection are witnessing a significant surge in interest due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship. Nowadays, by the virtue [...] Read more.

Cholesteric liquid crystal (ChLC) materials with broadband reflection are witnessing a significant surge in interest due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship. Nowadays, by the virtue of building self-organized nanostructures with pitch gradient or non-uniform pitch distribution, extensive work has already been performed to obtain ChLC films with a broad reflection band. This critical review systematically summarizes the optical background of the ChLCs with broadband reflection characteristics, methods to obtain broadband reflection of ChLCs, as well as the application in this area. Combined with the research status and the advantages in the field, the challenges and opportunities of applied scientific problems in the research direction are also introduced. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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17 pages, 14047 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Self-Assembly and Application of Para-Aramids

by Chunjie Xie, Shixuan Yang, Ran He, Jianning Liu, Yuexi Chen, Yongyi Guo, Zhaoxia Guo, Teng Qiu and Xinlin Tuo

Molecules 2022, 27(14), 4413; https://doi.org/10.3390/molecules27144413 - 9 Jul 2022

Cited by 11 | Viewed by 3716

Abstract

Poly(p-phenylene terephthalamide) (PPTA) is one kind of lyotropic liquid crystal polymer. Kevlar fibers performed from PPTA are widely used in many fields due to their superior mechanical properties resulting from their highly oriented macromolecular structure. However, the “infusible and insoluble” characteristic [...] Read more.

Poly(p-phenylene terephthalamide) (PPTA) is one kind of lyotropic liquid crystal polymer. Kevlar fibers performed from PPTA are widely used in many fields due to their superior mechanical properties resulting from their highly oriented macromolecular structure. However, the “infusible and insoluble” characteristic of PPTA gives rise to its poor processability, which limits its scope of application. The strong interactions and orientation characteristic of aromatic amide segments make PPTA attractive in the field of self-assembly. Chemical derivation has proved an effective way to modify the molecular structure of PPTA to improve its solubility and amphiphilicity, which resulted in different liquid crystal behaviors or supramolecular aggregates, but the modification of PPTA is usually complex and difficult. Alternatively, higher-order all-PPTA structures have also been realized through the controllable hierarchical self-assembly of PPTA from the polymerization process to the formation of macroscopic products. This review briefly summarizes the self-assembly methods of PPTA-based materials in recent years, and focuses on the polymerization-induced PPTA nanofibers which can be further fabricated into different macroscopic architectures when other self-assembly methods are combined. This monomer-started hierarchical self-assembly strategy evokes the feasible processing of PPTA, and enriches the diversity of product, which is expected to be expanded to other liquid crystal polymers. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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24 pages, 9105 KiB

Open AccessReview

Photothermal-Driven Liquid Crystal Elastomers: Materials, Alignment and Applications

by Wei Zhang, Yifei Nan, Zongxuan Wu, Yajing Shen and Dan Luo

Molecules 2022, 27(14), 4330; https://doi.org/10.3390/molecules27144330 - 6 Jul 2022

Cited by 16 | Viewed by 7838

Abstract

Liquid crystal elastomers (LCEs) are programmable deformable materials that can respond to physical fields such as light, heat, and electricity. Photothermal-driven LCE has the advantages of accuracy and remote control and avoids the requirement of high photon energy for photochemistry. In this review, [...] Read more.

Liquid crystal elastomers (LCEs) are programmable deformable materials that can respond to physical fields such as light, heat, and electricity. Photothermal-driven LCE has the advantages of accuracy and remote control and avoids the requirement of high photon energy for photochemistry. In this review, we discuss recent advances in photothermal LCE materials and investigate methods for mechanical alignment, external field alignment, and surface-induced alignment. Advances in the synthesis and orientation of LCEs have enabled liquid crystal elastomers to meet applications in optics, robotics, and more. The review concludes with a discussion of current challenges and research opportunities. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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28 pages, 10294 KiB

Open AccessReview

Recent Progress in Azopyridine-Containing Supramolecular Assembly: From Photoresponsive Liquid Crystals to Light-Driven Devices

by Hao Ren, Peng Yang and Haifeng Yu

Molecules 2022, 27(13), 3977; https://doi.org/10.3390/molecules27133977 - 21 Jun 2022

Cited by 11 | Viewed by 3704

Abstract

Azobenzene derivatives have become one of the most famous photoresponsive chromophores in the past few decades for their reversible molecular switches upon the irradiation of actinic light. To meet the ever-increasing requirements for applications in materials science, biomedicine, and light-driven devices, it is [...] Read more.

Azobenzene derivatives have become one of the most famous photoresponsive chromophores in the past few decades for their reversible molecular switches upon the irradiation of actinic light. To meet the ever-increasing requirements for applications in materials science, biomedicine, and light-driven devices, it is usually necessary to adjust their photochemical property from the molecular level by changing the substituents on the benzene rings of azobenzene groups. Among the diverse azobenzene derivatives, azopyridine combines the photoresponsive feature of azobenzene groups and the supramolecular function of pyridyl moieties in one molecule. This unique feature provides pH-responsiveness and hydrogen/halogen/coordination binding sites in the same chromophore, paving a new way to prepare multi-functional responsive materials through non-covalent interactions and reversible chemical reactions. This review summarizes the photochemical and photophysical properties of azopyridine derivatives in supramolecular states (e.g., hydrogen/halogen bonding, coordination interactions, and quaternization reactions) and illustrates their applications from photoresponsive liquid crystals to light-driven devices. We hope this review can highlight azopyridine as one more versatile candidate molecule for designing novel photoresponsive materials towards light-driven applications. Full article

(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)

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Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display

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