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Crystals
Special Issues
Liquid-Crystalline Ion Conductors
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Liquid-Crystalline Ion Conductors

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

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 17629

Special Issue Editor

Dr. Masafumi Yoshio

E-Mail Website
Guest Editor
1. National Institute for Materials Science, Research Center for Functional Materials, Center for Functional Sensor & Actuator, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
2. Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan
Interests: supramolecular chemistry; stimuli-responsive materials; liquid crystals; self-assembled nanofibers; organic ion and electron conductors; actuators; luminescent materials

Special Issue Information

Dear Colleagues,

The transportation of ions can be enhanced and switched using hierarchical and dynamic structures such as those formed by nanosegregatred liquid crystals and microphase-separated block copolymers. Achieving these functions should allow one not only to fabricate high-performance energy devices including capacitors, lithium batteries, solar cells, and fuell cells, but also to develop state-of-the-art ionic devices such as displays, non-volatile memories, acoustic devices, sensors, actuators, and new separation membranes for water purification. An example of conventional liquid-crystalline ion conductors is liquid-crystalline molecules tethering ion conducting moieties. Oligoethylene oxide or carbonate moieties can be employed for lithium ion conductors. Acidic groups such as sulfonic acid can be introduced into mesogenic molecules to develop proton conductors. Liquid crystals containing cationic, anionic, or zwitterionic moietes are called ionic liquid crystals, and they are also an important class of ion conductors, which can dissociate doped salts and acids into ions. In addition, there is another type of liquid-crystalline ion conductors based on two-component supramolecular assemblies of non-volatile ionic liquids and hydrogen-bonded mesomorphic molecules. To date, liquid crystal chemists have paid much attention to how the dimensions of ion transport can be controlled and then fixed into flexible solid films and how the conductivities of target ions are enhanced into liquid crystal structures from the point of view of supramolecular science and their practical applications. For such functionalization, it is important to design molecular shapes, intermolecular interactions, and segregation, and to further control the orientation of molecular assemblies in a macroscopic scale.

This Special Issue is aimed at both basic and applied research on liquid-crystalline ion conductors. We encourage the submission of original papers on the new design and synthesis of liquid crystals and polymers capable of transporting ions and their use in various applications. Topics for the issue will include the following: 

  • The synthesis and structural characterization of ionic liquid-crystalline assemblies
  • The alignment of assemblies and their fixation by polymerization
  • Electrochemical properties
  • Anisotropic properties
  • Stimuli-responsive properties upon photoirradiation, and applied electric and magnetic fields
  • Switching properties
  • Optical properties
  • Device applications

Dr. Masafumi Yoshio
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.

Keywords

  • synthesis and structural characterization of ionic liquid-crystalline assemblies
  • alignment of assemblies and their fixation by polymerization
  • electrochemical properties
  • anisotropic properties
  • stimuli-responsive properties upon photoirradiation and applied electric and magnetic fields
  • switching properties
  • optical properties
  • device applications

Published Papers (5 papers)

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Research

9 pages, 2900 KiB  
Article
Ion-Conductive Nanostructured Polymer Films Formed by Photopolymerization of Lyotropic Columnar Liquid-Crystalline Monomers, Composed of a Zwitterionic Compound and a Protic Ionic Liquid
by Siyu Cao, Masafumi Yoshio and Atsushi Seki
Crystals 2020, 10(4), 276; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10040276 - 06 Apr 2020
Cited by 2 | Viewed by 3515
Abstract
Here, we report on a new family of columnar nanostructured polymer films forming protic nanochannels that exhibit good ionic conductivities in the order of 10−4–10−3 S cm−1 at ambient temperature. These polymer films were obtained by the in situ [...] Read more.
Here, we report on a new family of columnar nanostructured polymer films forming protic nanochannels that exhibit good ionic conductivities in the order of 10−4–10−3 S cm−1 at ambient temperature. These polymer films were obtained by the in situ photopolymerization of lyotropic columnar liquid crystals, consisting of a polymerizable taper-shaped zwitterionic compound and a protic ionic liquid (imidazolium bis(trifluoromethylsulfonyl)imide), in the presence of 15 wt% water. The composition of the protic ionic liquid in the mixture was changed from 40 to 60 mol%. The ionic conductivities were measured by an alternating current impedance method. The ionic conductivity increased with the increase of the protic ionic liquid. The conductivities of columnar nanostructured polymer films were about 2–3 orders of magnitude higher than those of amorphous polymer films prepared by photopolymerization of the corresponding monomers in an isotropic liquid state. The formation of nanochannels in the polymer matrices significantly enhanced the ion conduction. The present two-component lyotropic liquid-crystalline self-assembly followed by photopolymerization is a promising approach to the development of high ion-conductive polymer membranes. Full article
(This article belongs to the Special Issue Liquid-Crystalline Ion Conductors)
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12 pages, 3182 KiB  
Article
Bicontinuous Cubic and Hexagonal Columnar Liquid Crystalline Ion-Conductors at Room Temperature in Ion-Doped Dendritic Amphiphiles
by Thi Huyen Do, Ho-Joong Kim, Manh Linh Nguyen and Byoung-Ki Cho
Crystals 2020, 10(3), 193; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10030193 - 11 Mar 2020
Cited by 6 | Viewed by 3631
Abstract
A bicontinuous cubic (Cubbi) liquid crystalline (LC) phase consisting of three dimensional (3D) conducting networks is a promising structural platform for ion-conductors. For practical applications using this fascinating LC structure, it is necessary to suppress crystallization at room temperature (RT). Herein, [...] Read more.
A bicontinuous cubic (Cubbi) liquid crystalline (LC) phase consisting of three dimensional (3D) conducting networks is a promising structural platform for ion-conductors. For practical applications using this fascinating LC structure, it is necessary to suppress crystallization at room temperature (RT). Herein, we report the Cubbi structure at RT and the morphology–dependent conduction behavior in ionic samples of a non-crystallizable dendritic amphiphile. In the molecular design, branched alkyl chains were used as an ionophobic part instead of crystallizable linear alkyl chains. Two ionic samples with Cubbi and hexagonal columnar (Colhex) LC phases at RT were prepared by adding different amounts of lithium salt to the amphiphile. Impedance analysis demonstrated that the Cubbi phase contributed to the faster ion-conduction to a larger extent than the Colhex phase due to the 3D ionic networks of the Cubbi phase. In addition, the temperature–dependent impedance and electric modulus data provided information regarding the phase transition from microphase-separated phase to molecularly mixed liquid phase. Full article
(This article belongs to the Special Issue Liquid-Crystalline Ion Conductors)
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11 pages, 3103 KiB  
Article
Effect of Noncovalent Dispersion of Poly(Ethylene Oxide) in Columnar Polyether-Based Discotic Liquid Crystal on the Ionic Conductivity and Dynamics of Lithium Ions
by Jih-Dar Hwang, Po-Ying Chen, Shang-Wu Ding and Chi Wi Ong
Crystals 2019, 9(12), 627; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9120627 - 28 Nov 2019
Cited by 5 | Viewed by 2523
Abstract
The ionic conductivity of an electrolyte is represented by a product of carrier density, charge (electric), and ionic mobility. The overall goal of this study was to provide an insight into the influence of lithium ion conductivity and dynamic when a continuous discotic [...] Read more.
The ionic conductivity of an electrolyte is represented by a product of carrier density, charge (electric), and ionic mobility. The overall goal of this study was to provide an insight into the influence of lithium ion conductivity and dynamic when a continuous discotic liquid crystal (DLC) matrix of hexaazatrinapthylene-polyether, HATN-TEG-1, is doped with a small amount of polyethylene oxide (PEO, 5% of MW 8000). The favorable non-covalent interactions between PEO and the DLC triethylene glycol side-chains is supported by the maintenance of the mesophase. The lithium ionic conductivity of HATN-TEG-1 was found to be 1.1 × 10−6 S cm−1, which is better than the corresponding HATN-TEG-1-5%PEO-8000 with a value of 6.06 × 10−7 S cm−1. These results are further supported by the dynamics of the lithium ions in HATN-TEG-1 and HATN-TEG-1-5%PEO-8000 as characterized by 7Li, and 1H NMR spin-lattice relaxation time and self-diffusion coefficient measurements. Though the additional PEO was found to increase the ion carriers, the significant lowering of the ionic conductivity may be attributed to the more pronounced decrease of the mobility of the ionic part when the HATN-TEG-1 matrix is dispersed with PEO. This finding indicates that the doping of 5% PEO onto the matrix of HATN-TEG-1 DLC has an adverse effect on both its diffusion rate and ion conductivity. Full article
(This article belongs to the Special Issue Liquid-Crystalline Ion Conductors)
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7 pages, 1472 KiB  
Article
Synthesis of an Adduct-Type Organic Ionic Crystal with Solid-State Ionic Conductivity from A Thiocyanate-Based Ionic Liquid and B(C6F5)3
by Yui Oki and Makoto Moriya
Crystals 2019, 9(11), 567; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9110567 - 29 Oct 2019
Cited by 3 | Viewed by 2927
Abstract
We synthesized the novel adduct-type organic ionic crystal [C3mim][SCN·B(C6F5)3] (1) by the reaction of 1–methyl–3–propylimidazolium thiocyanate ([C3mim][SCN]), which is a room temperature ionic liquid, and B(C6F5)3, a bulky Lewis [...] Read more.
We synthesized the novel adduct-type organic ionic crystal [C3mim][SCN·B(C6F5)3] (1) by the reaction of 1–methyl–3–propylimidazolium thiocyanate ([C3mim][SCN]), which is a room temperature ionic liquid, and B(C6F5)3, a bulky Lewis acid. The formation of a coordinative B–N bond between the SCN anion and the B(C6F5)3 in 1 was revealed by single-crystal X-ray diffractometry. We showed that 1 displays ionic conductivity in the crystalline state and that doping 1 with sodium thiocyanate and B(C6F5)3 results in a dramatic increase in ionic conductivity compared to that of 1. Full article
(This article belongs to the Special Issue Liquid-Crystalline Ion Conductors)
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9 pages, 2799 KiB  
Communication
Design of Ionic Liquid Crystals Forming Normal-Type Bicontinuous Cubic Phases with a 3D Continuous Ion Conductive Pathway
by Takahiro Ichikawa, Yui Sasaki, Tsubasa Kobayashi, Hikaru Oshiro, Ayaka Ono and Hiroyuki Ohno
Crystals 2019, 9(6), 309; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9060309 - 14 Jun 2019
Cited by 4 | Viewed by 4431
Abstract
We have prepared a series of pyridinium-based gemini amphiphiles. They exhibit thermotropic liquid–crystalline behavior depending on their alkyl chain lengths and anion species. By adjusting the alkyl chain lengths and selecting suitable anions, we have obtained an ionic amphiphile that exhibits a normal-type [...] Read more.
We have prepared a series of pyridinium-based gemini amphiphiles. They exhibit thermotropic liquid–crystalline behavior depending on their alkyl chain lengths and anion species. By adjusting the alkyl chain lengths and selecting suitable anions, we have obtained an ionic amphiphile that exhibits a normal-type bicontinuous cubic phase from 38 °C to 12 °C on cooling from an isotropic phase. In the bicontinuous cubic liquid–crystalline assembly, the pyridinium-based ionic parts align along a gyroid minimal surface forming a 3D continuous ionic domain while their ionophobic alkyl chains form 3D branched nanochannel networks. This ionic compound can form homogeneous mixtures with a lithium salt and the resultant mixtures keep the ability to form normal-type bicontinuous cubic phases. Ion conduction measurements have been performed for the mixtures on cooling. It has been revealed that the formation of the 3D branched ionophobic nanochannels does not disturb the ion conduction behavior in the ionic domain while it results in the conversion of the state of the mixtures from fluidic liquids to quasi-solids, namely highly viscous liquid crystals. Although the ionic conductivity of the mixtures is in the order of 10–7 S cm–1 at 40 °C, which is far lower than the values for practical use, the present material design has a potential to pave the way for developing advanced solid electrolytes consisting of two task-specific nanosegregated domains: One is an ionic liquid nano-domain with a 3D continuity for high ionic conductivity and the other is ionophobic nanochannel network domains for high mechanical strength. Full article
(This article belongs to the Special Issue Liquid-Crystalline Ion Conductors)
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