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Current Advances in Liquid Crystals II
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Current Advances in Liquid Crystals II

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Macromolecular Chemistry".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 18472

Special Issue Editors

Prof. Dr. Pradip K. Bhowmik

E-Mail Website
Guest Editor
Department of Chemistry and Biochemistry, University of Nevada Las Vegas, 4505 S. Maryland Parkway Box 454003, Las Vegas, NV 89154-4003, USA
Interests: liquid crystalline polymers; light-emitting polymers; fire retardant polymers; viologen polymers; poly(pyridinium salts); nanostructured materials; organic synthesis; polymer synthesis; green chemistry; ionic liquids; ionic liquid crystals; luminescent organic salts; anticancer drugs
Special Issues, Collections and Topics in MDPI journals
Dr. Alfonso Martinez-Felipe

E-Mail Website
Co-Guest Editor
School of Engineering, University of Aberdeen, Scotland, UK
Interests: liquid crystals; polymers; hydrogen bonding; supramolecular chemistry; Fourier-transform infrared spectroscopy - FT-IR; thermal analysis; dielectric spectroscopy; fuel cells; electrolytes; ionic conductivity; light-responsive materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The broad field of liquid crystals (LCs) has attracted the attention of chemists, physicists, biologists, and engineers alike since the discovery of liquid crystal phase by the Austrian botanist Friedrich Reinitzer in 1888. The LC phases combine the material properties of crystals with the flow properties of liquids. As such, they have provided the foundation for a revolution in the low-power, flat-panel display technology known as liquid crystal displays (LCDs). Interestingly enough, many diversified, chemical structural architectures (rod-shaped, disc-shaped, and bent-shaped, among others) do exhibit various types of LC phases that include organic molecules, ionic molecules, zwitter ionic molecules, main-chain polymers, side-chain polymers, combinations of main-chain and side-chain polymers, hyperbranced polymers, and dedrimers, to mention a few. They have many technogical applications because of their chemical diversities and types of LC phases. For example, Kevlar—lyotropic LC aromatic polyamide—and Vectra—thermotropic aromatic LC polyester—are the basis of light-weight, high-strength materials for a number of civilian and military applications including their important contribution to body armor. Side-chain LC polymers are known to be functional polymers for nonlinear optical properties and data storage capabilities. LC elastomers have gone beyond artifical muscles to use in 3D/4D printing in soft robotics and in biomedical devices. Additionally, ionic liquid crystals (ILCs) that form columnar, smectic, and bicontinuous cubic phases can provide well-organized 1D, 2D, and 3D channels capable of transporting ions and electrons. They can be used as electrolytes for batteries and photovoltaics, semiconductors, and electroluminescence and electrochemical devices. ILCs are the recent addition to the ever-increasing field of LCs.

Therefore, we invite researchers to submit original research articles and reviews to this Special Issue of Molecules on “Liquid Crystals” that aims to identify and review the latest research on liquid crystals that have been demonstrated to have a great impact in the field. Manuscripts can be related to any aspect of liquid crystals, including (but not limited to):

  • synthesis of novel LCs;
  • structure–property–application of LCs;
  • novel types of LCs;
  • supramolecular liquid crystals;
  • metal-containing LCs
  • applications of LCs in devices;
  • biological applications of LCs;
  • physical properties of LCs;
  • computer simulations of the phase behaviour of LCs; and
  • theoretical models of LCs.

Prof. Dr. Pradip K. Bhowmik
Dr. Alfonso Martinez-Felipe
Guest Editors

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. Molecules 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 2700 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
  • ionic liquid crystals
  • zwitter ionic liquid crystals
  • nanostructured liquid crystals
  • thermotropic liquid crystals
  • lyotropic liquid crystals
  • amphotropic liquid crystals
  • liquid crystal elastomers
  • rod-shaped molecules
  • disc-shaped molecules
  • bent-shaped molecules

Related Special Issue

Published Papers (6 papers)

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Research

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10 pages, 2094 KiB  
Article
Insertion of the Liquid Crystal 5CB into Monovacancy Graphene
by Paul A. Brown, Jakub Kołacz, Sean A. Fischer, Christopher M. Spillmann and Daniel Gunlycke
Molecules 2022, 27(5), 1664; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27051664 - 03 Mar 2022
Cited by 1 | Viewed by 1768
Abstract
Interfacial interactions between liquid crystal (LC) and two-dimensional (2D) materials provide a platform to facilitate novel optical and electronic material properties. These interactions are uniquely sensitive to the local energy landscape of the atomically thick 2D surface, which can be strongly influenced by [...] Read more.
Interfacial interactions between liquid crystal (LC) and two-dimensional (2D) materials provide a platform to facilitate novel optical and electronic material properties. These interactions are uniquely sensitive to the local energy landscape of the atomically thick 2D surface, which can be strongly influenced by defects that are introduced, either by design or as a byproduct of fabrication processes. Herein, we present density functional theory (DFT) calculations of the LC mesogen 4-cyan-4′-pentylbiphenyl (5CB) on graphene in the presence of a monovacancy (MV-G). We find that the monovacancy strengthens the binding of 5CB in the planar alignment and that the structure is lower in energy than the corresponding homeotropic structure. However, if the molecule is able to approach the monovacancy homeotropically, 5CB undergoes a chemical reaction, releasing 4.5 eV in the process. This reaction follows a step-by-step process gradually adding bonds, inserting the 5CB cyano group into MV-G. We conclude that this irreversible insertion reaction is likely spontaneous, potentially providing a new avenue for controlling both LC behavior and graphene properties. Full article
(This article belongs to the Special Issue Current Advances in Liquid Crystals II)
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17 pages, 3293 KiB  
Article
Controlling Liquid Crystal Configuration and Phase Using Multiple Molecular Triggers
by Linda M. Oster, Jake Shechter, Benjamin Strain, Manisha Shivrayan, Sankaran Thai Thayumanavan and Jennifer L. Ross
Molecules 2022, 27(3), 878; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27030878 - 27 Jan 2022
Cited by 2 | Viewed by 2777
Abstract
Liquid crystals are able to transform a local molecular interaction into a macroscopic change of state, making them a valuable “smart” material. Here, we investigate a novel polymeric amphiphile as a candidate for molecular triggering of liquid crystal droplets in aqueous background. Using [...] Read more.
Liquid crystals are able to transform a local molecular interaction into a macroscopic change of state, making them a valuable “smart” material. Here, we investigate a novel polymeric amphiphile as a candidate for molecular triggering of liquid crystal droplets in aqueous background. Using microscopy equipped with crossed polarizers and optical tweezers, we find that the monomeric amphiphile is able to trigger both a fast phase change and then a subsequent transition from nematic to isotropic. We next include sodium dodecyl sulfate (SDS), a standard surfactant, with the novel amphiphilic molecules to test phase transitioning when both were present. As seen previously, we find that the activity of SDS at the surface can result in configuration changes with hysteresis. We find that the presence of the polymeric amphiphile reverses the hysteresis previously observed during such transitions. This work demonstrates a variety of phase and configuration changes of liquid crystals that can be controlled by multiple exogenous chemical triggers. Full article
(This article belongs to the Special Issue Current Advances in Liquid Crystals II)
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7 pages, 16256 KiB  
Communication
Control of the Induced Handedness of Helical Nanofilaments Employing Cholesteric Liquid Crystal Fields
by Ju-Yong Kim, Jae-Jin Lee, Jun-Sung Park, Yong-Jun Choi and Suk-Won Choi
Molecules 2021, 26(19), 6055; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26196055 - 06 Oct 2021
Cited by 2 | Viewed by 1545
Abstract
In this paper, a simple and powerful method to control the induced handedness of helical nanofilaments (HNFs) is presented. The nanofilaments are formed by achiral bent-core liquid crystal molecules employing a cholesteric liquid crystal field obtained by doping a rod-like nematogen with a [...] Read more.
In this paper, a simple and powerful method to control the induced handedness of helical nanofilaments (HNFs) is presented. The nanofilaments are formed by achiral bent-core liquid crystal molecules employing a cholesteric liquid crystal field obtained by doping a rod-like nematogen with a chiral dopant. Homochiral helical nanofilaments are formed in the nanophase-separated helical nanofilament/cholesteric phase from a mixture with a cholesteric phase. This cholesteric phase forms at a temperature higher than the temperature at which the helical nanofilament in a bent-core molecule appears. Under such conditions, the cholesteric liquid crystal field acts as a driving force in the nucleation of HNFs, realizing a perfectly homochiral domain consisting of identical helical nanofilament handedness. Full article
(This article belongs to the Special Issue Current Advances in Liquid Crystals II)
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15 pages, 2952 KiB  
Article
Mesomorphic Behavior of Symmetric Azomethine Dimers Containing Different Chromophore Groups
by Elena Perju and Luminita Marin
Molecules 2021, 26(8), 2183; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26082183 - 10 Apr 2021
Cited by 9 | Viewed by 1885
Abstract
A series of new azomethine dimers was synthesized by the condensation reaction of flexible bis-benzaldehydes with four aromatic amines containing phenyl, naphthyl, anthracene and pyrene groups. Their right structure was confirmed by FTIR and 1H-NMR spectroscopy and their thermal properties were investigated [...] Read more.
A series of new azomethine dimers was synthesized by the condensation reaction of flexible bis-benzaldehydes with four aromatic amines containing phenyl, naphthyl, anthracene and pyrene groups. Their right structure was confirmed by FTIR and 1H-NMR spectroscopy and their thermal properties were investigated by thermogravimetric analysis, differential scanning calorimetry and polarized light optical microscopy. A view on their photophysical behavior was gained by UV-vis and photoluminescence spectroscopy. The dimers containing pyrene and anthracene presented liquid crystalline behavior, while the other dimers were crystalline compounds. Two dimers containing pyrene moieties formed mesomorphic glasses and had intense luminescence, promising properties for applications in building optoelectronic devices. Full article
(This article belongs to the Special Issue Current Advances in Liquid Crystals II)
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Review

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36 pages, 4908 KiB  
Review
Development and Application of Liquid Crystals as Stimuli-Responsive Sensors
by Sulayman A. Oladepo
Molecules 2022, 27(4), 1453; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27041453 - 21 Feb 2022
Cited by 17 | Viewed by 3845
Abstract
This focused review presents various approaches or formats in which liquid crystals (LCs) have been used as stimuli-responsive sensors. In these sensors, the LC molecules adopt some well-defined arrangement based on the sensor composition and the chemistry of the system. The sensor usually [...] Read more.
This focused review presents various approaches or formats in which liquid crystals (LCs) have been used as stimuli-responsive sensors. In these sensors, the LC molecules adopt some well-defined arrangement based on the sensor composition and the chemistry of the system. The sensor usually consists of a molecule or functionality in the system that engages in some form of specific interaction with the analyte of interest. The presence of analyte brings about the specific interaction, which then triggers an orientational transition of the LC molecules, which is optically discernible via a polarized optical image that shows up as dark or bright, depending on the orientation of the LC molecules in the system (usually a homeotropic or planar arrangement). The various applications of LCs as biosensors for glucose, protein and peptide detection, biomarkers, drug molecules and metabolites are extensively reviewed. The review also presents applications of LC-based sensors in the detection of heavy metals, anionic species, gases, volatile organic compounds (VOCs), toxic substances and in pH monitoring. Additionally discussed are the various ways in which LCs have been used in the field of material science. Specific attention has been given to the sensing mechanism of each sensor and it is important to note that in all cases, LC-based sensing involves some form of orientational transition of the LC molecules in the presence of a given analyte. Finally, the review concludes by giving future perspectives on LC-based sensors. Full article
(This article belongs to the Special Issue Current Advances in Liquid Crystals II)
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24 pages, 52702 KiB  
Review
Flexible Liquid Crystal Polymer Technologies from Microwave to Terahertz Frequencies
by Zepeng Zhou, Wenqing Li, Jun Qian, Weihong Liu, Yiming Wang, Xijian Zhang, Qinglei Guo, Yevhen Yashchyshyn, Qingpu Wang, Yanpeng Shi and Yifei Zhang
Molecules 2022, 27(4), 1336; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27041336 - 16 Feb 2022
Cited by 15 | Viewed by 5464
Abstract
With the emergence of fifth-generation (5G) cellular networks, millimeter-wave (mmW) and terahertz (THz) frequencies have attracted ever-growing interest for advanced wireless applications. The traditional printed circuit board materials have become uncompetitive at such high frequencies due to their high dielectric loss and large [...] Read more.
With the emergence of fifth-generation (5G) cellular networks, millimeter-wave (mmW) and terahertz (THz) frequencies have attracted ever-growing interest for advanced wireless applications. The traditional printed circuit board materials have become uncompetitive at such high frequencies due to their high dielectric loss and large water absorption rates. As a promising high-frequency alternative, liquid crystal polymers (LCPs) have been widely investigated for use in circuit devices, chip integration, and module packaging over the last decade due to their low loss tangent up to 1.8 THz and good hermeticity. The previous review articles have summarized the chemical properties of LCP films, flexible LCP antennas, and LCP-based antenna-in-package and system-in-package technologies for 5G applications, although these articles did not discuss synthetic LCP technologies. In addition to wireless applications, the attractive mechanical, chemical, and thermal properties of LCP films enable interesting applications in micro-electro-mechanical systems (MEMS), biomedical electronics, and microfluidics, which have not been summarized to date. Here, a comprehensive review of flexible LCP technologies covering electric circuits, antennas, integration and packaging technologies, front-end modules, MEMS, biomedical devices, and microfluidics from microwave to THz frequencies is presented for the first time, which gives a broad introduction for those outside or just entering the field and provides perspective and breadth for those who are well established in the field. Full article
(This article belongs to the Special Issue Current Advances in Liquid Crystals II)
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