Liquid Crystal Research and Novel Applications in the 21st Century

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Liquid Crystals".

Deadline for manuscript submissions: 30 July 2024 | Viewed by 3701

Special Issue Editor


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Guest Editor
Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
Interests: liquid crystals; chiral liquid crystals; ferroelectric liquid crystals; polymer stabilized liquid crystals; nanoparticles in anisotropic fluids; liquid crystal-nanotube dispersions; defects and defect dynamics; phase ordering in soft matter; fractal structures
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Special Issue Information

Dear Colleagues,

For many years, the main focus of liquid crystal (LC) research was on either the fundamental properties of anisotropic fluids or applications in liquid crystal displays (LCDs). This has changed quite dramatically in the last decade, since displays and monitors have matured considerably and have become the market’s dominating technology. From a physics point of view, fundamental LC research has spread into many other areas of soft matter science, such as polymers, colloids, biological materials, dispersions, medical and pharmaceutical systems, and fundamental phenomena in physics. From a chemistry point of view, increasingly complicated molecular structures have been developed; moreover, dendrimers, ionic liquid crystals, green chemistry approaches and recycling aspects of displays have emerged. In terms of applications, liquid crystals have expanded into the fields of adaptive optics, augmented reality, optical elements, telecommunication, optical solitons and lasers, as well as other devices outside the field of Liquid Crystal Displays.

This Special Issue will highlight the latest important developments in the research and applications of liquid crystal. It will include topics beyond the traditional liquid crystal investigations of past decades, focusing on recent studies that have propelled the field of soft matter systems and application development. Moreover, we anticipate that this collection of reviews, research papers, perspective articles and roadmaps will demonstrate the multi-disciplinarity, diversity and variety of liquid crystals, LC-related systems and composites, combining aspects of physics and chemistry with those of material science, mathematics, biology and medicine.

Given the broad range of liquid crystal-related topics covered in this collection, the submission deadline has been set to 30 June 2024 to give authors sufficient time to prepare their contributions.

Research areas include, but are not limited to:

  • New nematic systems (ferroelectric, biaxial and twist-bend nematics);
  • Active liquid crystals;
  • Instabilities, pattern formation, solitons and topological defects;
  • Nanostructured systems (PSLCs, PDLCs, elastomers, actuators and gels);
  • Colloidal liquid crystals (cellulose nanocrystals, graphene oxide LCs, clays, nano-rods, etc.);
  • Biological and bio-inspired liquid crystal systems;
  • Frustrated phases;
  • Photosensitive liquid crystals and surfaces;
  • Theory and simulation of liquid crystal-based systems;
  • Optics, photonics, and non-linear optical devices;
  • Conductive liquid crystal devices;
  • Optical films, gratings and smart devices;
  • LC lasers;
  • Drug delivery;
  • Liquid crystal-based sensors;
  • LCs in medicine.

Dr. Ingo Dierking
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. Crystals is an international peer-reviewed open access monthly 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.

Published Papers (4 papers)

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Research

9 pages, 2636 KiB  
Article
Polarization Coupling between Ferroelectric Liquids and Ferroelectric Solids: Effects of the Fringing Field Profile
by Stefano Marni, Raouf Barboza, Ayomide S. Oluwajoba, Riccardo Zamboni and Liana Lucchetti
Crystals 2024, 14(5), 425; https://doi.org/10.3390/cryst14050425 - 29 Apr 2024
Viewed by 533
Abstract
Recent experiments devoted to characterizing the behavior of sessile ferroelectric liquid droplets on ferroelectric solid substrates have shown the existence of a droplet electromechanical Rayleigh-like instability. The instability is induced by the bulk polarization of the ferroelectric fluid, which couples to the polarization [...] Read more.
Recent experiments devoted to characterizing the behavior of sessile ferroelectric liquid droplets on ferroelectric solid substrates have shown the existence of a droplet electromechanical Rayleigh-like instability. The instability is induced by the bulk polarization of the ferroelectric fluid, which couples to the polarization of the underlying substrate through its fringing field and solid–fluid interface coupling. With the aim of characterizing this phenomenon, namely the coupling between the polarizations of a fluid and a solid material, we studied the behavior of ferroelectric liquid droplets confined between two solid substrates, arranged in different configurations, realized to generate fringing fields with different profiles. The results show that the features of the droplets instability are indeed affected by the specific fringing field shape in a way dominated by the minimization of the electrostatic energy associated with the bulk polarization of the ferroelectric fluid. Full article
(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)
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12 pages, 4848 KiB  
Article
Structural Study of Nematogenic Compound 5OS5
by Aleksandra Deptuch, Bartosz Sęk, Sebastian Lalik, Wojciech Zając, Mirosława D. Ossowska-Chruściel, Janusz Chruściel and Monika Marzec
Crystals 2024, 14(4), 367; https://doi.org/10.3390/cryst14040367 - 13 Apr 2024
Viewed by 865
Abstract
The S-(4-pentylphenyl) 4-(pentyloxy)benzothioate, forming the nematic phase, is investigated by X-ray diffraction in temperatures between 263 K and 365 K, with the support of differential scanning calorimetry and polarizing optical microscopy. The microscopic observations show changes within the solid state, while X-ray diffraction [...] Read more.
The S-(4-pentylphenyl) 4-(pentyloxy)benzothioate, forming the nematic phase, is investigated by X-ray diffraction in temperatures between 263 K and 365 K, with the support of differential scanning calorimetry and polarizing optical microscopy. The microscopic observations show changes within the solid state, while X-ray diffraction does not indicate any transitions between the crystal phases. The Rietveld refinement shows that the crystal phase formed from the melt is the same monoclinic crystal phase with the P21/c space group as reported for a single crystal grown from an ethanol solution. The temperature dependence of the unit cell parameters in the 263–335 K range is determined and the coefficients of thermal expansion are obtained. The unit cell expands on heating along the longer ac-diagonal and b-axis while, along the shorter ac-diagonal, a very small shrinkage occurs. The diffraction patterns of the liquid crystalline nematic phase indicate the formation of dimers via hydrogen bonding. Density functional theory calculations (def2TZVPP basis set, B3LYP-D3(BJ) correlation-exchange functional) are applied for geometry optimization of an isolated molecule and selected dimers. Full article
(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)
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15 pages, 1318 KiB  
Article
Analysing the Photo-Physical Properties of Liquid Crystals
by Jordan Hobbs, Johan Mattsson and Mamatha Nagaraj
Crystals 2024, 14(4), 362; https://doi.org/10.3390/cryst14040362 - 11 Apr 2024
Viewed by 765
Abstract
Intrinsically fluorescent liquid crystals are highly sought after for a variety of applications. Most of the measurements of photo-physical properties of liquid crystals are made in dilute solutions, which is mainly due to the relative ease of both these measurements and the interpretation [...] Read more.
Intrinsically fluorescent liquid crystals are highly sought after for a variety of applications. Most of the measurements of photo-physical properties of liquid crystals are made in dilute solutions, which is mainly due to the relative ease of both these measurements and the interpretation of data. The fluorescence spectra depend on a number of parameters including the concentration in liquid crystal solutions, the device geometry, and the mesophase in which the spectra have been measured. Working with neat, or concentrated, liquid crystal samples adds experimental complexities such as the inner filter effect (IFE), which affects the collection of data, interpretation of the results, and accuracy of the conclusions. In this paper, we present a systematic study of the photo-physical properties of both a model reference material, Nile red, and a nematic liquid crystal, 4-cyano-4′-pentylbiphenyl (5CB). The influence on the emission spectra of an increasing solute concentration is investigated and discussed. Moreover, a detailed investigation of the influence of the used device geometry, as well as the choice of appropriate data fitting methodologies, are presented. Full article
(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)
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11 pages, 2073 KiB  
Article
Reconfigurable Liquid Crystal Elastomer Director Patterns for Multi-Mode Shape Morphing
by Xianbing Zeng, Tianfeng Zhou, Lei Li, Juncai Song, Ruijue Duan, Xiang Xiao, Baiqian Xu, Guanghao Wu and Yubing Guo
Crystals 2024, 14(4), 357; https://doi.org/10.3390/cryst14040357 - 10 Apr 2024
Viewed by 760
Abstract
Liquid crystal elastomers (LCEs) are a monolithic material with programmable three-dimensional (3D) morphing modes stemming from their designable non-uniform molecular orientations (or director). However, the shape morphing mode is generally fixed when director patterns of LCEs are determined. Multi-mode shape morphing is difficult [...] Read more.
Liquid crystal elastomers (LCEs) are a monolithic material with programmable three-dimensional (3D) morphing modes stemming from their designable non-uniform molecular orientations (or director). However, the shape morphing mode is generally fixed when director patterns of LCEs are determined. Multi-mode shape morphing is difficult to achieve since director patterns cannot be reconfigured. Herein, we demonstrate the ability to reconfigure LCE director patterns and initial shapes—and thus shape morphing modes—by the manual assembly and de-assembly of LCE pixels. We measured the mechanical properties of LCEs with and without UV glue and found their Young’s moduli were 9.6 MPa and 11.6 MPa. We firstly fabricate LCE pixels with designed director fields and then assemble 24 pixels with required director fields into an LCE film with a designed director pattern, which corresponds to a programmed shape morphing mode. We further exhibit that we can de-assemble the LCE film back into original pixels or new pixels with different shapes and then re-assemble them into a new film with a different initial shape and director pattern, which corresponds to a second programmed shape morphing mode. Principally, we can have a large amount of shape morphing modes if we have enough pixels. The demonstrated capability of multi-mode shape morphing enhances functions of LCEs, which broadens their applications in soft robotics, programmable origami/kirigami, responsive surfaces, and so on. Full article
(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)
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