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Crystals
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State-of-the-Art Liquid Crystals Research in Japan (2nd Edition)
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State-of-the-Art Liquid Crystals Research in Japan (2nd Edition)

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

Deadline for manuscript submissions: closed (30 September 2025) | Viewed by 6479

Special Issue Editors

Dr. Shigeyuki Yamada

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Guest Editor
Kyoto Institute of Technology, Faculty of Molecular Chemistry and Engineering, Kyoto, Japan
Interests: organic synthesis; fluorine; liquid crystals; fluorescence; phosphorescence; stimulus-responsive materials
Special Issues, Collections and Topics in MDPI journals
Dr. Mizuho Kondo

E-Mail Website
Guest Editor
Department of Applied Chemistry, Graduate School of Engineering, University of Hyogo, Hyogo 651-2197, Japan
Interests: liquid crystals; fluorescence; mechanochromism; polymer
Special Issues, Collections and Topics in MDPI journals
Dr. Kosuke Kaneko

E-Mail Website
Guest Editor
Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, Kyoto 603-8577, Japan
Interests: liquid crystals; electrorheology; elastomer; siloxane
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Liquid crystals (LCs) are substances with properties intermediate between those of crystals and liquids; they exhibit liquid properties (fluidity) and the optical anisotropy of crystals. LC molecules mainly consist of a rigid π structure and a flexible chain unit, which provide some directional order (orientation); however, they do not have positional order. With thermotropic or lyotropic phase transitions between the crystal, LC, and liquid phases, the molecular aggregates can be reversibly arranged and predicted by molecular dynamic simulations. The alteration of molecular aggregates is well known to significantly affect various physical behaviors, specifically photophysical, optical, electrical, and chemical characteristics. Therefore, consolidating the results of cutting-edge liquid crystal research into a single Special Issue will greatly contribute to future developments in the fields of chemistry, materials, optics, and electronics.

In 2022 and 2023, we gathered ten excellent papers by Japanese researchers and published them in the Special Issue "State-of-the-Art Liquid Crystals Research in Japan". Following on the success of this Special Issue, in 2024, we will once again collect papers for a Special Issue entitled "State-of-the-Art Liquid Crystals Research in Japan (2nd Edition)", in which we will include research results from a wide range of innovative fields, such as chemistry, physics, optics, photonics, optical alignment technology, materials, and devices, related to liquid crystal research originating in Japan.

Potential topics include, but are not limited to, the following:

  1. Exploration of novel LC materials;
  2. Development of functional materials with LC characteristics;
  3. Characterization of the structures of LC phases;
  4. Exploration of simulation techniques for LC materials;
  5. Applications using LC materials.

Dr. Shigeyuki Yamada
Dr. Mizuho Kondo
Dr. Kosuke Kaneko
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 250 words) can be sent to the Editorial Office for assessment.

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 2100 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
  • blue phase
  • stimulus responsiveness
  • photoalignment control
  • molecular dynamics simulations
  • rheology
  • X-ray diffraction
  • luminescence
  • electrical conductivity

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Further information on MDPI's Special Issue policies can be found here.

Related Special Issue

Published Papers (5 papers)

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Research

13 pages, 4030 KB  
Article
Selenoether-Linked Liquid Crystal Trimers and the Twist-Bend Nematic Phase
by Yuki Arakawa and Takuma Shiba
Crystals 2026, 16(1), 69; https://doi.org/10.3390/cryst16010069 - 21 Jan 2026
Viewed by 484
Abstract
Bent-shaped liquid crystal (LC) dimers, trimers, and oligomers are intriguing because of their unique liquid crystallinities, which have gained further impetus after the identification of the twist-bend nematic (NTB) phase in these molecules. LC trimers exhibiting the NTB phase still [...] Read more.
Bent-shaped liquid crystal (LC) dimers, trimers, and oligomers are intriguing because of their unique liquid crystallinities, which have gained further impetus after the identification of the twist-bend nematic (NTB) phase in these molecules. LC trimers exhibiting the NTB phase still remain relatively rare compared to the predominant LC dimers. We report the first homologs of selenium-linked LC trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylseleno)alkoxy]biphenyls (CBSenOBOnSeCB) with carbon numbers in the alkyl-chain spacers, n = 7 or 9). Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction (XRD) measurements were performed to investigate the phase transition behavior and mesophase structures of the trimers. Both CBSenOBOnSeCB trimers exhibited nematic (N) and NTB phases. The XRD measurements revealed the presence of smectic A-like cybotactic clusters with a triply intercalated structure in the N and NTB phases. The LC phase transition temperatures of CBSenOBOnSeCB were lower than those of the already-known ether-linked CBOnOBOnOCB and thioether-linked CBSnOBOnSCB counterparts. This trend is ascribed to the enhanced molecular bending and molecular flexibility of CBSenOBOnSeCB, which are caused by the smaller bond angle and greater bond flexibility of C–Se–C compared to C–O–C and C–S–C. This study offers a new molecular design for multiply linked LC oligomers with heavier chalcogen atoms. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in Japan (2nd Edition))
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12 pages, 1984 KB  
Article
Electric-Field Actuation of Liquid Crystalline Elastomer Films
by Mizuho Sawada, Kosuke Kaneko, Kiyomi Fuchigami, Kimiyoshi Kaneko, Hirohiko Washiya and Tomonori Hanasaki
Crystals 2026, 16(1), 16; https://doi.org/10.3390/cryst16010016 - 26 Dec 2025
Viewed by 1016
Abstract
Liquid crystal elastomers (LCEs) are soft, stimuli-responsive materials capable of converting molecular-scale reorientation of mesogenic groups into macroscopic, reversible deformations. In this study, film-shaped LCEs were fabricated via a thiol–ene click reaction and characterized under varying electric-field strengths and tensile loads. The LCEs [...] Read more.
Liquid crystal elastomers (LCEs) are soft, stimuli-responsive materials capable of converting molecular-scale reorientation of mesogenic groups into macroscopic, reversible deformations. In this study, film-shaped LCEs were fabricated via a thiol–ene click reaction and characterized under varying electric-field strengths and tensile loads. The LCEs exhibited pronounced soft elasticity and large, reversible strains due to reorientation of mesogenic groups, in contrast to non-mesogenic elastomers. Dynamic viscoelastic measurements revealed fully reversible changes in storage modulus upon electric-field application, highlighting the critical role of mesogenic group alignment in electromechanical actuation. Electric-field-induced contraction increased with field strength and decreased with tensile load, reaching a maximum of 15% under minimal load, with additional enhancement resulting from mesogenic group reorientation along the thickness direction. Notably, unlike conventional light- or temperature-driven actuation, which is often limited by slow molecular relaxation or heat diffusion, the electric-field-driven LCE exhibited rapid, fully reversible deformation. These findings demonstrate the potential of electric-field-responsive LCEs for applications requiring fast, controllable, and large-strain actuation, and provide insights into the interplay between mesogenic group orientation, mechanical loading, and external stimuli in designing efficient soft actuators. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in Japan (2nd Edition))
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17 pages, 3533 KB  
Article
Ferroelectric Properties and Ambipolar Carrier Transport of 9-Fluorenone-Based Liquid Crystals
by Sou-un Doi, Syota Yamada, Ken’ichi Aoki and Atsushi Seki
Crystals 2025, 15(12), 1021; https://doi.org/10.3390/cryst15121021 - 28 Nov 2025
Viewed by 864
Abstract
The functional integration of chiral liquid crystals and π-conjugated compounds has great potential for creating novel exotic materials. A series of chiral donor–acceptor (D–A)-type fluorenone derivatives was synthesized to investigate the influence of molecular structure upon their liquid-crystalline phase-transition behavior, ferroelectricity, photophysical properties, [...] Read more.
The functional integration of chiral liquid crystals and π-conjugated compounds has great potential for creating novel exotic materials. A series of chiral donor–acceptor (D–A)-type fluorenone derivatives was synthesized to investigate the influence of molecular structure upon their liquid-crystalline phase-transition behavior, ferroelectricity, photophysical properties, and photoconductive properties. Polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analyses revealed that several D–A-type fluorenone derivatives exhibited liquid crystal (LC) phases. These chiral LC fluorenone derivatives exhibited polarization hysteresis in the chiral smectic C (SmC*) phase. Among the four fluorenone-based ferroelectric liquid crystals (FLCs), (R,R)-2a exhibited the largest spontaneous polarization (over 3.0 × 102 nC cm−2). The formation of intramolecular charge-transfer (ICT) states in each compound was evidenced by the UV–vis absorption spectroscopy. Ambipolar carrier transport in the SmC* phases of the fluorenone-based FLCs was elucidated by the time-of-flight (TOF) method. The mobilities of holes and electrons in the SmC* phases were on the order of 10−5 cm2 V−1 s−1, which is on par with the carrier mobilities of low-ordered smectic phases in conventional LC semiconductors. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in Japan (2nd Edition))
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17 pages, 3150 KB  
Article
Design of Near-UV Photoluminescent Liquid-Crystalline Dimers: Roles of Fluorinated Aromatic Ring Position and Flexible Linker
by Sorato Inui, Hayato Kitaoka, Yuto Eguchi, Motohiro Yasui, Tsutomu Konno and Shigeyuki Yamada
Crystals 2025, 15(10), 840; https://doi.org/10.3390/cryst15100840 - 27 Sep 2025
Cited by 4 | Viewed by 1131
Abstract
Near-ultraviolet photoluminescence liquid-crystalline molecules (PLLCs) have attracted attention for temperature-responsive photoluminescence (PL) modulation and ON/OFF sensing under external stimuli. We recently developed mesogenic dimers composed of two hexyloxy-substituted, fluorinated tolane-type cores linked by alkylene-1,n-dioxy chains that exhibited near-UV PL in the [...] Read more.
Near-ultraviolet photoluminescence liquid-crystalline molecules (PLLCs) have attracted attention for temperature-responsive photoluminescence (PL) modulation and ON/OFF sensing under external stimuli. We recently developed mesogenic dimers composed of two hexyloxy-substituted, fluorinated tolane-type cores linked by alkylene-1,n-dioxy chains that exhibited near-UV PL in the solid state. However, the formation of LC phases and the temperature range of the LC state were limited. To improve LC phase stability, in this study, we extended the flexible terminal chains and repositioned the fluorinated aromatic rings from the outer to the inner core positions. Accordingly, we synthesized mesogenic dimers with even-numbered alkylene-1,n-dioxy linkers (hexylene, octylene, and decylene) and outer- or inner-ring fluorination. Outer-ring fluorination led to high melting temperatures and stable crystalline phases with limited mesophase formation. In contrast, inner-ring fluorination induced nematic phases upon heating and cooling owing to zig-zag molecular structures that disrupted crystallinity. Photophysical studies confirmed near-UV PL in solution and solid states; however, the quantum yield of the solution PL was low (<0.01). In the solid state, the PL efficiencies and wavelengths were influenced by the fluorinated aromatic ring position and linker length. This study provides important molecular design criteria for developing stable LC materials with tunable near-UV luminescence for temperature-responsive optical devices. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in Japan (2nd Edition))
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14 pages, 1591 KB  
Article
Synergistic Control of Liquid Crystallinity and Phosphorescence in Gold(I) Complexes via Strategic Alkyl Chain Design
by Arushi Rawat, Kohsuke Matsumoto, Ganesan Prabusankar and Osamu Tsutsumi
Crystals 2025, 15(6), 554; https://doi.org/10.3390/cryst15060554 - 10 Jun 2025
Viewed by 2104
Abstract
Liquid crystals exhibit unique properties that can be tailored in response to external stimuli. Significant research is directed toward the development of luminescent materials exhibiting liquid crystallinity for various applications. The present work reports Au(I) complexes featuring N-heterocyclic carbene and phenyl acetylide ligands. [...] Read more.
Liquid crystals exhibit unique properties that can be tailored in response to external stimuli. Significant research is directed toward the development of luminescent materials exhibiting liquid crystallinity for various applications. The present work reports Au(I) complexes featuring N-heterocyclic carbene and phenyl acetylide ligands. Metal complexes enable the utilization of the triplet excitons through their inherent spin–orbit coupling, promoting intersystem crossing from singlet (Sn) to triplet (Tn) states to observe room-temperature phosphorescence (RTP). The strong bonds between carbene and Au enhance the thermal stability, and the substituted benzimidazole ring alters the thermodynamic and photophysical properties of the complexes. Incorporating the acetylide ligands with long alkoxy chains led to the formation of liquid crystalline (LC) phases, which exhibited stability over a wide temperature range. Additionally, the luminescence behavior was affected by the ethynyl ligands, and high quantum yields of RTP were observed. This study establishes the development of LC Au(I) complexes with a thermodynamically stable LC mesophase over a wide temperature range for applications in the field of light-emitting functional materials. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in Japan (2nd Edition))
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