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Advances in Liquid Crystals
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Advances in Liquid Crystals

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Soft Matter".

Deadline for manuscript submissions: closed (20 April 2023) | Viewed by 7566

Special Issue Editor

Dr. Richard J. Mandle

E-Mail Website
Guest Editor
School of Physics and Astronomy, University of Leeds, Leeds, UK
Interests: soft matter; liquid crystals; organic synthesis; materials chemistry; nanomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Liquid crystals combine the flow properties of a liquid with the orientational and/or positional ordering of the solid state. The discovery of liquid crystals in the late 19th century generated immense scientific interest, eventually leading to the development of liquid crystal displays (LCD) in the second half of the 20th century. LCD technology enabled low-power, high information density displays to become a reality and helped to change the way we access and consume information and media.

In the 21st century, the interest in liquid crystalline materials and their applications has shown no signs of abatement, and much progress has been achieved in the development of novel materials, new applications of liquid crystalline materials, and new theoretical insights. Of particular interest is the recent discovery of polar nematic phases which display a giant ferroelectric response.

This Special Issue aims to highlight some of the recent advances in liquid crystals which have taken place in the early part of this century, such as the discovery of new mesophases, new materials classes, functional liquid crystalline materials, modulated liquid crystalline phases, mesophases in biological systems, LC polymers and elastomers, nanoparticle dispersions, guest–host liquid crystal systems and devices, active nematics and collective motion, chromonic and lyotropic systems, liquid crystalline actuators, liquid crystalline photonic materials, and liquid crystalline organic electronics.

Dr. Richard Mandle
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • liquid crystals
  • nematics
  • ferroelectric nematics
  • soft matter
  • thermotropics
  • photonics
  • elastomers
  • soft actuators
  • self-organization
  • complex matter

Published Papers (4 papers)

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Research

8 pages, 2196 KiB  
Communication
Effect of Nematogen Doping in Bent-Core Molecular Systems with a Helical Nanofilament and Dark Conglomerate
by Jae-Jin Lee and Suk-Won Choi
Materials 2023, 16(2), 548; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16020548 - 05 Jan 2023
Cited by 1 | Viewed by 1094
Abstract
Two types of binary mixtures were prepared. One consisted of a calamitic nematogen and bent-core molecule with a helical nanofilament, whereas the other contained a calamitic nematogen and bent-core molecule with a dark conglomerate. The chiroptical features of these two mixtures were investigated [...] Read more.
Two types of binary mixtures were prepared. One consisted of a calamitic nematogen and bent-core molecule with a helical nanofilament, whereas the other contained a calamitic nematogen and bent-core molecule with a dark conglomerate. The chiroptical features of these two mixtures were investigated using polarized optical microscopy and circular dichroism. In addition, X-ray diffraction analysis was performed on the two binary mixtures. The chiroptical features of the two mixtures were remarkably different. One mixture showed enhanced chiroptical features, whereas the other did not show chiroptical features. This method may help in distinguishing between helical nanofilaments and dark conglomerates which originate from bent-core molecular systems. Full article
(This article belongs to the Special Issue Advances in Liquid Crystals)
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15 pages, 4037 KiB  
Article
Direct Observation of Biaxial Nematic Order in Auxetic Liquid Crystal Elastomers
by Zhenming Wang, Thomas Raistrick, Aidan Street, Matthew Reynolds, Yanjun Liu and Helen F. Gleeson
Materials 2023, 16(1), 393; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16010393 - 31 Dec 2022
Cited by 4 | Viewed by 1684
Abstract
Auxetic materials exhibit a negative Poisson’s ratio, i.e., they become thicker rather than thinner in at least one dimension when strained. Recently, a nematic liquid crystal elastomer (LCE) was shown to be the first synthetic auxetic material at a molecular level. Understanding the [...] Read more.
Auxetic materials exhibit a negative Poisson’s ratio, i.e., they become thicker rather than thinner in at least one dimension when strained. Recently, a nematic liquid crystal elastomer (LCE) was shown to be the first synthetic auxetic material at a molecular level. Understanding the mechanism of the auxetic response in LCEs is clearly important, and it has been suggested through detailed Raman scattering studies that it is related to the reduction of uniaxial order and emergence of biaxial order on strain. In this paper, we demonstrate direct observation of the biaxial order in an auxetic LCE under strain. We fabricated ~100 μm thick LCE strips with complementary geometries, exhibiting either planar or homeotropic alignment, in which the auxetic response is seen in the thickness or width of the sample, respectively. Polarized Raman scattering measurements on the planar sample show directly the reduction in the uniaxial order parameters on strain and suggest the emergence of biaxial order to mediate the auxetic response in the sample thickness. The homeotropic sample is studied via conoscopy, allowing direct observation of both the auxetic response in the width of the sample and increasing biaxiality in the LCE as it is strained. We verified that the mechanism of the auxetic response in auxetic LCEs is due to the emergence of the biaxial order and conclude such materials can be added to the small number of biaxial nematic systems that have been observed. Importantly, we also show that the mechanical Frèedericksz transition seen in some LCEs is consistent with a strain-induced transition from an optically positive to an optically negative biaxial system under strain, rather than a director rotation in a uniaxial system. Full article
(This article belongs to the Special Issue Advances in Liquid Crystals)
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13 pages, 2956 KiB  
Article
Thioether-Linked Liquid Crystal Trimers: Odd–Even Effects of Spacers and the Influence of Thioether Bonds on Phase Behavior
by Yuki Arakawa, Kenta Komatsu, Yuko Ishida, Takuma Shiba and Hideto Tsuji
Materials 2022, 15(5), 1709; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15051709 - 24 Feb 2022
Cited by 9 | Viewed by 1969
Abstract
We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3–11). All CBSnOBOnSCB [...] Read more.
We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3–11). All CBSnOBOnSCB homologs exhibited LC phases. Interestingly, even-n and odd-n homologs showed monotropic layered smectic A (SmA) and pseudo-layered twist-bend nematic (NTB) phases, respectively, below a nematic (N) phase. This alternate formation, which depends on spacer chain parity, is attributed to different average molecular shapes, which are associated with the relative orientations of the biphenyl moieties: linear and bent shapes for even-n and odd-n homologs, respectively. In addition, X-ray diffraction analysis indicated a strong cybotactic N phase tendency, with a triply intercalated structure. The phase-transition behavior and LC phase structures of thioether-linked CBSnOBOnSCB were compared with those of the all-ether-linked classic LC trimers CBOnOBOnOCB. Overall, thioether linkages endowed CBSnOBOnSCB with a monotropic LC tendency and lowered phase-transition temperatures, compared to those of CBOnOBOnOCB, for the same n. This is attributed to enhanced flexibility and bending (less molecular anisotropy) of the molecules, caused by the greater bond flexibility and smaller inner bond angles of the C–S–C bonds, compared to those of the C–O–C bonds. Full article
(This article belongs to the Special Issue Advances in Liquid Crystals)
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17 pages, 3146 KiB  
Article
On the Miscibility of Nematic Liquid Crystals with Ionic Liquids and Joint Reaction for High Helical Twisting Power Product(s)
by Maciej Czajkowski, Joanna Feder-Kubis, Bartłomiej Potaniec, Łukasz Duda and Joanna Cybińska
Materials 2022, 15(1), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15010157 - 26 Dec 2021
Cited by 2 | Viewed by 2305
Abstract
Mixtures of nematic liquid crystals (LCs) with chiral ionic liquids (CILs) may find application as active materials for electrically driven broadband mirrors. Five nematic liquid crystal hosts were mixed with twenty three ionic liquids, including chiral ones, and studied [...] Read more.
Mixtures of nematic liquid crystals (LCs) with chiral ionic liquids (CILs) may find application as active materials for electrically driven broadband mirrors. Five nematic liquid crystal hosts were mixed with twenty three ionic liquids, including chiral ones, and studied in terms of their miscibility within the nematic phase. Phase diagrams of the mixtures with CILs which exhibited twisted nematic phase were determined. Miscibility, at levels between 2 and 5 wt%, was found in six mixtures with cyanobiphenyl-based liquid crystal host—E7. On the other hand, the highest changes in the isotropization temperature was found in the mixtures with isothiocyanate-based liquid crystal host—1825. Occurrence of chemical reactions was found. A novel chiral binaphtyl-based organic salt [N11116][BNDP] was synthesized and, in reaction to the 1825 host, resulted in high helical twisting power product(s). Selectivity of the reaction with the isothiocyanate-based liquid crystal was found. Full article
(This article belongs to the Special Issue Advances in Liquid Crystals)
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