Research

21 pages, 9451 KiB

Open AccessArticle

Design and Investigation of a Side-Chain Liquid Crystalline Polysiloxane with a N_tb-Phase-Forming Side Chain

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Wanhe Jiang

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Georg H. Mehl

Crystals 2023, 13(12), 1614; https://doi.org/10.3390/cryst13121614 - 21 Nov 2023

Viewed by 276

Abstract

A new mesogenic non-symmetric dimeric monomer with a terminal olefin function, forming a twist bend nematic (N_tb) as well as a nematic (N) phase, was synthesized, using an enhanced synthetic methodology, which avoids isomerization of the terminal double bond in the [...] Read more.

A new mesogenic non-symmetric dimeric monomer with a terminal olefin function, forming a twist bend nematic (N_tb) as well as a nematic (N) phase, was synthesized, using an enhanced synthetic methodology, which avoids isomerization of the terminal double bond in the preparation of the dimer. This monomer was attached to a pentamethyldisiloxane group, resulting in the SmA LC phase behavior of the ensuing material. Linking the monomer to a siloxane main chain resulted in nematic phase behavior. Detailed studies with the N_tb phase forming dimer DTC5C7 show full miscibility of the dimer and the new LC polymer in the LC state, suggesting that the side-chain LC polymer forms a N_tb phase as the low-temperature nematic phase. Copolymerizing the monomer with a cyanobiphenyl-based monomer allows us to tune the glass transition and phase behavior further. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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13 pages, 13885 KiB

Open AccessFeature PaperArticle

Effect of Liquid Crystalline Acrylates on the Electro-Optical Properties and Micro-Structures of Polymer-Dispersed Liquid Crystal Films

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Crystals 2023, 13(9), 1294; https://doi.org/10.3390/cryst13091294 - 22 Aug 2023

Viewed by 581

Abstract

Polymer-dispersed liquid-crystal (PDLC) films have wide applications in light shutters, smart windows for cars and buildings, dimming glasses, and smart peep-proof films due to their switchable optical states under electrical fields as well as large area processibility. They are usually prepared with liquid [...] Read more.

Polymer-dispersed liquid-crystal (PDLC) films have wide applications in light shutters, smart windows for cars and buildings, dimming glasses, and smart peep-proof films due to their switchable optical states under electrical fields as well as large area processibility. They are usually prepared with liquid crystals (LCs) and non-liquid crystalline monomers (NLCMs). Introduction of liquid crystalline monomers (LCMs) into PDLCs might spark new functionality or high-performance devices such as polymer-dispersed and -stabilized liquid crystals. In this study, the effect of molecular structures and doping concentrations of acrylate LCMs on the electro-optical properties and micro-structures of PDLC films is systematically studied. The pore size of polymer networks and the driving voltage of the PDLC films are affected by the molecular polarity and degree of functionality of the LCMs. The electro-optical properties of the PDLC films are affected by the synergistic influence of molecular structure of LCMs and micro-structures of PDLCs. These results might provide the experimental and theoretical basis for constructing the relationship between the molecular structure of LCM, micro-structure and electro-optical response of PDLC films. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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13 pages, 9329 KiB

Open AccessArticle

Colored PDLC Films with Wide Gamut Range

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Crystals 2023, 13(8), 1216; https://doi.org/10.3390/cryst13081216 - 05 Aug 2023

Viewed by 572

Abstract

Due to the discoloration properties under different applied voltages, dye-doped polymer-dispersed liquid crystal (PDLC) films are widely used as camouflage nets and invisibility cloaks. However, the range of the discoloration has an intuitive effect on their applications. In this work, we studied the [...] Read more.

Due to the discoloration properties under different applied voltages, dye-doped polymer-dispersed liquid crystal (PDLC) films are widely used as camouflage nets and invisibility cloaks. However, the range of the discoloration has an intuitive effect on their applications. In this work, we studied the gamut range of PDLC film doped with dyes of red, green, blue, and yellow, with the concentration corresponding to the minimum haze of these dyes. The influence of the applied voltage on the color range of single-layer and double-layer films with different backgrounds was studied. The relationship of the voltage with the color was set from 0 V to 60 V at steps of 5 V, to characterize the discoloration of the PDLC films. The results showed that the films could cover 42.48% of the sRGB gamut and even exceed the range. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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13 pages, 5049 KiB

Open AccessArticle

Synthesis of Thiophene-Based Derivatives and the Effects of Their Molecular Structure on the Mesomorphic Behavior and Temperature Range of Liquid-Crystalline Blue Phases

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Crystals 2023, 13(6), 916; https://doi.org/10.3390/cryst13060916 - 06 Jun 2023

Viewed by 548

Abstract

The development of blue-phase liquid crystal (BPLC) materials with a wide temperature range is of great significance for practical applications in the optoelectronic field. In the study, bent-core derivatives with a 3-hexyl-2,5-disubstituted thiophene central ring in the λ-shaped molecular structure were designed and [...] Read more.

The development of blue-phase liquid crystal (BPLC) materials with a wide temperature range is of great significance for practical applications in the optoelectronic field. In the study, bent-core derivatives with a 3-hexyl-2,5-disubstituted thiophene central ring in the λ-shaped molecular structure were designed and synthesized. Their mesomorphic behavior and effect on the blue-phase (BP) temperature range were investigated. Interestingly, a BP was achieved both during the heating and cooling processes by doping with a proper concentration of chiral compound into the thiophene bent-shaped molecule with high rigidity, while derivatives with fluorine atom substitution only exhibited cholesteric phase no matter how many chiral compounds were added. This result proved that BP is highly sensitive to the molecular structures of bent-shaped molecules. Moreover, the BP temperature range was broadened when adding these molecules into a BPLC host, which thus improved the BP temperature range from the initial value, no more than 4 °C, to as much as 24 °C. The experimental phenomena were reasonably explained through molecular simulation calculations. The study may provide some experimental basis and theoretical guidance for the design of novel bent-shaped molecules and BPLC material with a wide temperature range. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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13 pages, 8480 KiB

Open AccessArticle

Role of Hydroxy Group in the Electro-Optical Properties of Polymer-Dispersed Liquid Crystals

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Crystals 2023, 13(5), 843; https://doi.org/10.3390/cryst13050843 - 19 May 2023

Cited by 2 | Viewed by 847

Abstract

In this work, hydroxylated compounds are applied to prepare polymer-dispersed liquid crystal (PDLC) films and the role of the hydroxy group is studied in detail by comparing the effects of the hydroxylated acrylate monomer, the hydroxylated mesogenic component and their corresponding non-hydroxylated components. [...] Read more.

In this work, hydroxylated compounds are applied to prepare polymer-dispersed liquid crystal (PDLC) films and the role of the hydroxy group is studied in detail by comparing the effects of the hydroxylated acrylate monomer, the hydroxylated mesogenic component and their corresponding non-hydroxylated components. It is revealed that the hydroxylated acrylate monomer plays a more important role in modifying the morphology of the polymer matrix and thereby the electro-optical performance of the PDLC films. Parameters of the polymer matrix, such as size and density of voids, can be affected by various components, but only the hydroxylated acrylate monomer can alter its type from the typical Swiss-cheese type to the polymer-microsphere type. Essentially, the hydroxylated mesogenic component takes effect through changing the ratio of the liquid crystal phase, while the hydroxylated acrylate monomer can participate in the polymerization and impact the development of the polymer matrix. It is anticipated that this research can help in understanding the role of the hydroxy group in PDLC films. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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14 pages, 8566 KiB

Open AccessArticle

Research on the Morphology, Electro-Optical Properties and Mechanical Properties of Electrochromic Polymer-Dispersed Liquid Crystalline Films Doped with Anthraquinone Dyes

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Crystals 2023, 13(5), 735; https://doi.org/10.3390/cryst13050735 - 27 Apr 2023

Cited by 3 | Viewed by 1003

Abstract

In this paper, dye-doped polymer-dispersed liquid crystalline (DDPDLC) films were prepared with high mechanical properties and low driving voltage by doping different dichroic anthraquinone dyes. The effects of various dye and doping concentrations on microscopic morphology, electro-optical characteristics, and mechanical characteristics were investigated. [...] Read more.

In this paper, dye-doped polymer-dispersed liquid crystalline (DDPDLC) films were prepared with high mechanical properties and low driving voltage by doping different dichroic anthraquinone dyes. The effects of various dye and doping concentrations on microscopic morphology, electro-optical characteristics, and mechanical characteristics were investigated. The optimal doping concentrations of different dyes were also explored. The results show that the addition of all dyes decreased the contrast ratio (CR) and the transmittance and mechanical properties of the polymer-dispersed liquid crystalline (PDLC) films. Similar mechanisms underlie the effects of solvent red 111 and solvent blue 104, which lower the driving voltages of the PDLC films. With the increasing concentration of the dye, the haze of the films first decreased and then increased after the content of the dye reached a certain level. For PDLC films doped with solvent green 28, the driving voltage and haze increased with the increasing content of the dye. According to different influencing factors, the dye content corresponding to the best performance of solvent red 111, solvent green 28 and solvent blue 104 is 0.8 wt%, 2.0 wt% and 0.3 wt%. Electrochromic PDLC films have been prepared based on the research results of dye content. The mechanical properties, electro-optical properties and microstructures of the films have been studied. The results show that the DDPDLC films could change color by tuning the applied voltages. The research provides a theoretical basis for obtaining PDLC films with a wider color gamut and supports the practical application of visible light camouflage technology in the military. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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10 pages, 3743 KiB

Open AccessArticle

Effect of Curing Temperature on the Properties of Electrically Controlled Dimming Film with Wide Working Temperature Range

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Crystals 2022, 12(11), 1551; https://doi.org/10.3390/cryst12111551 - 30 Oct 2022

Cited by 2 | Viewed by 1010

Abstract

In this paper, a polymer dispersed liquid crystal (PDLC) film with good electro-optical properties and wide working temperature range was prepared by the UV-polymerization induced phase separation (PIPS) method by optimizing the curing temperature using a LC with wide temperature range. The investigation [...] Read more.

In this paper, a polymer dispersed liquid crystal (PDLC) film with good electro-optical properties and wide working temperature range was prepared by the UV-polymerization induced phase separation (PIPS) method by optimizing the curing temperature using a LC with wide temperature range. The investigation found that when the polymerization temperature was at the clearing point of the prepolymer/LC mixture, the film had better electro-optical properties and a high contrast ratio of 51 at 90 °C, and the rise time and decay time were respectively as fast as 241.5 ms and 1750 ms at −20 °C. This study provides further methodological guidance for the curing process of PDLC film, and promotes its application in outdoor smart windows. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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8 pages, 1315 KiB

Open AccessArticle

The Effect of Chemically Modified Multi-Walled Carbon Nanotubes on the Electro-Optical Properties of a Twisted Nematic Liquid Crystal Display Mode

by

Zheng Ma

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Yanzi Gao

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Hui Cao

Crystals 2022, 12(10), 1482; https://doi.org/10.3390/cryst12101482 - 19 Oct 2022

Cited by 1 | Viewed by 1013

Abstract

In this study, we have chemically modified multi-walled carbon nanotubes (MWNTs) with different side chains for better dispersion in liquid crystal solutions, and fabricated twisted nematic liquid crystal cells doped with such MWNT derivatives. The introduction of MWNT derivatives affects the alignment of [...] Read more.

In this study, we have chemically modified multi-walled carbon nanotubes (MWNTs) with different side chains for better dispersion in liquid crystal solutions, and fabricated twisted nematic liquid crystal cells doped with such MWNT derivatives. The introduction of MWNT derivatives affects the alignment of LC molecules with or without external electric fields. Electro-optical property tests showed that the contrast ratio changed slightly with the sharp decrease in drive voltage, improving the drive ability of the twisted nematic liquid crystal display (TN-LCD) mode. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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12 pages, 2237 KiB

Open AccessArticle

Evaluation of the Skin Permeation-Enhancing Abilities of Newly Developed Water-Soluble Self-Assembled Liquid Crystal Formulations Based on Hexosomes

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Crystals 2022, 12(9), 1238; https://doi.org/10.3390/cryst12091238 - 01 Sep 2022

Cited by 4 | Viewed by 1214

Abstract

The present study aimed to develop polyethylene glycol–liquid crystals (PEG-LC) ointment formulations, assess their formulation characteristics, and establish their biocompatibility and impact on transdermal drug administration. PEG-LC formulations were prepared using a hydrophilic molecule, p-aminobenzoic acid (PAB). Formulation characterizations such as small-angle [...] Read more.

The present study aimed to develop polyethylene glycol–liquid crystals (PEG-LC) ointment formulations, assess their formulation characteristics, and establish their biocompatibility and impact on transdermal drug administration. PEG-LC formulations were prepared using a hydrophilic molecule, p-aminobenzoic acid (PAB). Formulation characterizations such as small-angle X-ray scattering, viscosity, pH, zeta potential, and the particle sizes of the formulations were examined to determine the physicochemical properties of the prepared formulations. The drug release profile of PEG-LC ointment formulations was assessed with a dialysis membrane. In vitro skin permeation testing was performed to establish whether the PEG-LC formulations improved drug skin penetration. The MTT and comet assays were performed to assess the biocompatibility of the formulations. Our data showed that the method is effective in forming hexosome-type PEG-LC formulations and that they were biocompatible. Furthermore, the PEG-LC formulations significantly improved PAB skin penetration when compared with commercial PEG. The PEG-LC formulation is a promising carrier for the delivery of hydrophilic drugs. Full article

(This article belongs to the Special Issue Liquid Crystal Phases and Phase Transitions)

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