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Liquid Crystal-Assisted Advanced Functional Materials

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 January 2018) | Viewed by 78782

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Special Issue Editors

Prof. Dr. M. Blanca Ros

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Instituto de Nanociencia y Materiales de Aragón (INMA), Química Orgánica, Facultad de Ciencias, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Interests: bent-core liquid crystals; liquid crystal-based materials, supramolecular functional materials; biomaterials

Dr. Raquel Giménez

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Guest Editor

Instituto de Nanociencia y Materiales de Aragón (INMA), and Dpto de Química Orgánica, Facultad de Ciencias, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Interests: nanostructured functional organic materials; self-assembly; supramolecular liquid crystals; supramolecular polymers; supramolecular chirality; chemistry of organic materials; luminescent liquid crystals; luminescent organogels

Dr. Teresa Sierra

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Guest Editor

Instituto de Ciencia de Materiales de Aragón, Química Orgánica, Facultad de Ciencias, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Interests: liquid crystals; supramolecular chirality; supramolecular electronics; self-assembled materials; dendrimers; drug-delivery

Special Issue Information

Dear Colleagues,

The combination of mobility and order in liquid crystals allows them to respond to a variety of external stimuli, and this is undoubtedly an inspiring feature for the design of smart materials. In the last few years, liquid crystals have emerged as a vehicle to control the organization of matter, from the micro- to the nanoscale, through the exploitation of mesogenic driving forces to self-organize molecules into defined arrangements. As a matter of fact, the diversity of liquid crystals, calamitic, discotic, bent-core or lyotropic mesophases, and their special responses to light, temperature, electric field, magnetic field or mechanical stress, among others, provide a myriad of opportunities in the field of functional materials. Both attributes, organization and responsiveness, situate liquid crystalline materials at the forefront of the investigation and progress of those materials that rely on a well-organized internal structure to display advanced functional properties.

Nowadays, optoelectronics, membranes or nanoparticles are employing mesophases as arranging media for the preparation of innovative materials with tuneable properties. Additionally, liquid crystalline materials endowed with photoactive abilities have arisen as very appealing and multi-stimuli responsive systems and actuators. In addition to this, processing materials through mesophases yields high performance materials and devices.

With this Special Issue, we aim to highlight some new stimulating reports on liquid crystals paving the way toward advanced functional materials, focussing from fundamental aspects through applications and future perspectives. We would like to take this opportunity to invite contributions from experts working on the design, synthesis, preparation, characterization or application of functional materials that have identified and selected liquid crystals as a smart and elegant working tool for their purposes, welcoming both original research papers, as well as review articles.

Prof. M. Blanca Ros
Dr. Raquel Giménez
Dr. Teresa Sierra
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. 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

Stimuli-responsive liquid crystals
Photonics
Optoelectronics
Organic electronics
Actuators
Membranes
Nanomaterials
Sensing and detecting
Biomedical applications
Other LC-based functional materials

Published Papers (11 papers)

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Research

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16 pages, 2363 KiB

Open AccessFeature PaperArticle

Electrospun Composite Liquid Crystal Elastomer Fibers

by Anshul Sharma and Jan P. F. Lagerwall

Materials 2018, 11(3), 393; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11030393 - 07 Mar 2018

Cited by 23 | Viewed by 8698

Abstract

We present a robust method to prepare thin oriented nematic liquid crystalline elastomer-polymer (LCE-polymer) core-sheath fibers. An electrospinning setup is utilized to spin a single solution of photo-crosslinkable low molecular weight reactive mesogens and a support polymer to form the coaxial LCE-polymer fibers, where the support polymer forms the sheath via in situ phase separation as the solvent evaporates. We discuss the effect of phase separation and compare two different sheath polymers (polyvinylpyrrolidone and polylactic acid), investigating optical and morphological properties of obtained fibers, as well as the shape changes upon heating. The current fibers show only irreversible contraction, the relaxation most likely being hindered by the presence of the passive sheath polymer, increasing in stiffness on cooling. If the sheath polymer can be removed while keeping the LCE core intact, we expect LCE fibers produced in this way to have potential to be used as actuators, for instance in soft robotics and responsive textiles. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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9 pages, 333 KiB

Open AccessArticle

Development of Coarse-Grained Liquid-Crystal Polymer Model with Efficient Electrostatic Interaction: Toward Molecular Dynamics Simulations of Electroactive Materials

by Kenji Tagashira, Kazuaki Z. Takahashi, Jun-ichi Fukuda and Takeshi Aoyagi

Materials 2018, 11(1), 83; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11010083 - 06 Jan 2018

Cited by 10 | Viewed by 5240

Abstract

Liquid-crystal polymers (LCPs) are well known materials for functional sensor and actuators, because of their high-responsiveness to an electric field. Owing to their complex physical nature, however, the prediction of the functions of LCPs is a challenge. To attack this problem from a molecular point of view, a simulation study is a promising approach. In this work, for future applications of molecular dynamics simulations to problems involving an electric field, we develop an LCP model which consists of coarse-grained mesogenic molecules and smeared charges. For the smearing function of the electrostatic force, the Gauss error function is introduced. This smearing is optimized to attain a reasonable accuracy for phase transition phenomena of liquid crystal while numerical instabilities arising from the singularity of the Coulomb potential are circumvented. For swelling systems, our LCP model exhibits the characteristics of both liquid crystals and unentangled polymer chains; orientational order of the mesogenic units and Rouse-like relaxation dynamics. Our coarse-grained LCP model successfully incorporates electric charges and dipoles and is therefore applicable to problems concerning an electric field. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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14 pages, 2254 KiB

Open AccessArticle

Charge Transport and Phase Behavior of Imidazolium-Based Ionic Liquid Crystals from Fully Atomistic Simulations

by Michael J. Quevillon and Jonathan K. Whitmer

Materials 2018, 11(1), 64; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11010064 - 02 Jan 2018

Cited by 15 | Viewed by 5434 | Correction

Abstract

Ionic liquid crystals occupy an intriguing middle ground between room-temperature ionic liquids and mesostructured liquid crystals. Here, we examine a non-polarizable, fully atomistic model of the 1-alkyl-3-methylimidazolium nitrate family using molecular dynamics in the constant pressure–constant temperature ensemble. These materials exhibit a distinct “smectic” liquid phase, characterized by layers formed by the molecules, which separate the ionic and aliphatic moieties. In particular, we discuss the implications this layering may have for electrolyte applications. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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7939 KiB

Open AccessArticle

New SmAP_F Mesogens Designed for Analog Electrooptics Applications

by Eva D. Korblova, Edward Guzman, Joseph E. Maclennan, Matthew A. Glaser, Renfan Shao, Edgardo Garcia, Yongqiang Shen, Rayshan Visvanathan, Noel A. Clark and David M. Walba

Materials 2017, 10(11), 1284; https://0-doi-org.brum.beds.ac.uk/10.3390/ma10111284 - 09 Nov 2017

Cited by 4 | Viewed by 3896

Abstract

We have previously reported the first realization of an orthogonal ferroelectric bent-core SmAP_F phase by directed design in mesogens with a single tricarbosilane-terminated alkoxy tail. Given the potentially useful electrooptic properties of this phase, including analog phase-only electrooptic index modulation with optical latching, we have been exploring its “structure space”, searching for novel SmAP_F mesogens. Here, we report two classes of these—the first designed to optimize the dynamic range of the index modulation in parallel-aligned cells by lowering the bend angle of the rigid core, and the second expanding the structure space of the phase by replacing the tricarbosilane-terminated alkyl tail with a polyfluorinated polyethylene glycol oligomer. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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1766 KiB

Open AccessCommunication

Design of Viologen-Based Liquid Crystals Exhibiting Bicontinuous Cubic Phases and Their Redox-Active Behavior

by Tsubasa Kobayashi and Takahiro Ichikawa

Materials 2017, 10(11), 1243; https://0-doi-org.brum.beds.ac.uk/10.3390/ma10111243 - 27 Oct 2017

Cited by 11 | Viewed by 5552

Abstract

We have succeeded in developing viologen-based liquid-crystalline materials forming bicontinuous cubic phases. They are composed of amphiphilic zwitterions with a viologen ionic-head-group and sulfonyl-imide-type acids. In the bicontinuous cubic liquid-crystalline assemblies, the ionic-head groups of the amphiphiles align along a gyroid minimal surface, forming a 3D continuous viologen layer. The ionic state of the viologen-moieties can be tuned from a dication state (V²⁺) to a radical mono cation state (V^1+•) by UV irradiation and/or electric field. This redox reaction proceeds in bulk, accompanying the change of their color from colorless to purple. Interestingly, they preserve the 3D molecular assembled structures beyond the redox reaction, which has been confirmed by polarizing optical microscopy and X-ray diffraction measurements. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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3260 KiB

Open AccessArticle

Organic Solid-State Tri-Wavelength Lasing from Holographic Polymer-Dispersed Liquid Crystal and a Distributed Feedback Laser with a Doped Laser Dye and a Semiconducting Polymer Film

by Minghuan Liu, Yonggang Liu, Zenghui Peng, Shaoxin Wang, Qidong Wang, Quanquan Mu, Zhaoliang Cao and Li Xuan

Materials 2017, 10(5), 509; https://0-doi-org.brum.beds.ac.uk/10.3390/ma10050509 - 07 May 2017

Cited by 2 | Viewed by 5082

Abstract

Organic solid-state tri-wavelength lasing was demonstrated from dye-doped holographic polymer-dispersed liquid crystal (HPDLC) distributed feedback (DFB) laser with semiconducting polymer poly[-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) and laser dye [4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran] (DCM) by a one-step holography technique, which centered at 605.5 nm, 611.9 nm, and 671.1 nm. The temperature-dependence tuning range for the tri-wavelength dye-doped HPDLC DFB laser was as high as 8 nm. The lasing emission from the 9th order HPDLC DFB laser with MEH-PPV as active medium was also investigated, which showed excellent s-polarization characterization. The diffraction order is 9th and 8th for the dual-wavelength lasing with DCM as the active medium. The results of this work provide a method for constructing the compact and cost-effective all solid-state smart laser systems, which may find application in scientific and applied research where multi-wavelength radiation is required. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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Review

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18 pages, 3675 KiB

Open AccessFeature PaperReview

Recent Advances in Discotic Liquid Crystal-Assisted Nanoparticles

by Ashwathanarayana Gowda and Sandeep Kumar

Materials 2018, 11(3), 382; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11030382 - 05 Mar 2018

Cited by 31 | Viewed by 6864

Abstract

This article primarily summarizes recent advancement in the field of discotic liquid crystal (DLC) nanocomposites. Discotic liquid crystals are nanostructured materials, usually 2 to 6 nm size and have been recognized as organic semiconducting materials. Recently, it has been observed that the dispersion of small concentration of various functionalized zero-, one- and two-dimensional nanomaterials in the supramolecular order of mesophases of DLCs imparts negligible impact on liquid crystalline properties but enhances their thermal, supramolecular and electronic properties. Synthesis, characterization and dispersion of various nanoparticles in different discotics are presented. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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21 pages, 2849 KiB

Open AccessFeature PaperReview

Liquid Crystal Elastomers—A Path to Biocompatible and Biodegradable 3D-LCE Scaffolds for Tissue Regeneration

by Marianne E. Prévôt, Senay Ustunel and Elda Hegmann

Materials 2018, 11(3), 377; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11030377 - 03 Mar 2018

Cited by 52 | Viewed by 9831

Abstract

The development of appropriate materials that can make breakthroughs in tissue engineering has long been pursued by the scientific community. Several types of material have been long tested and re-designed for this purpose. At the same time, liquid crystals (LCs) have captivated the scientific community since their discovery in 1888 and soon after were thought to be, in combination with polymers, artificial muscles. Within the past decade liquid crystal elastomers (LCE) have been attracting increasing interest for their use as smart advanced materials for biological applications. Here, we examine how LCEs can potentially be used as dynamic substrates for culturing cells, moving away from the classical two-dimensional cell-culture nature. We also briefly discuss the integration of a few technologies for the preparation of more sophisticated LCE-composite scaffolds for more dynamic biomaterials. The anisotropic properties of LCEs can be used not only to promote cell attachment and the proliferation of cells, but also to promote cell alignment under LCE-stimulated deformation. 3D LCEs are ideal materials for new insights to simulate and study the development of tissues and the complex interplay between cells. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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18 pages, 9888 KiB

Open AccessReview

Nanoporous Polymers Based on Liquid Crystals

by Jody Lugger, Dirk Jan Mulder, Rint Sijbesma and Albert Schenning

Materials 2018, 11(1), 104; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11010104 - 11 Jan 2018

Cited by 30 | Viewed by 8193

Abstract

In the present review, we discuss recent advances in the field of nanoporous networks based on polymerisable liquid crystals. The field has matured in the last decade, yielding polymers having 1D, 2D, and 3D channels with pore sizes on the nanometer scale. Next to the current progress, some of the future challenges are presented, with the integration of nanoporous membranes in functional devices considered as the biggest challenge. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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10638 KiB

Open AccessFeature PaperReview

Thermotropic Liquid Crystal-Assisted Chemical and Biological Sensors

by Nicolai Popov, Lawrence W. Honaker, Maia Popova, Nadezhda Usol’tseva, Elizabeth K. Mann, Antal Jákli and Piotr Popov

Materials 2018, 11(1), 20; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11010020 - 23 Dec 2017

Cited by 67 | Viewed by 13380

Abstract

In this review article, we analyze recent progress in the application of liquid crystal-assisted advanced functional materials for sensing biological and chemical analytes. Multiple research groups demonstrate substantial interest in liquid crystal (LC) sensing platforms, generating an increasing number of scientific articles. We review trends in implementing LC sensing techniques and identify common problems related to the stability and reliability of the sensing materials as well as to experimental set-ups. Finally, we suggest possible means of bridging scientific findings to viable and attractive LC sensor platforms. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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4536 KiB

Open AccessFeature PaperReview

Upgrading the Performance of Cholesteric Liquid Crystal Lasers: Improvement Margins and Limitations

by Josu Ortega, César L. Folcia and Jesús Etxebarria

Materials 2018, 11(1), 5; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11010005 - 21 Dec 2017

Cited by 40 | Viewed by 5056

Abstract

The topic of cholesteric-liquid-crystal lasers is a rapidly expanding research area in the field of soft-matter photonics. The increasing interest in this field is due to the high versatility that these lasers may possibly present and the prospects of giving rise to new miniaturized devices. However, further improvements in their operation capabilities are still required for potential applications. In this paper, we critically analyze the main strategies proposed up to now to optimize their performance. We show theoretically and experimentally that possible innovations in the device structure cannot produce lasers with threshold energies below a certain limit. This limit is determined by the light scattering and absorption losses inside the liquid crystal. Even assuming the case of samples free of defects and perfectly non-absorbing, an intrinsic light scattering, typical of mesogens, still remains. Numerical estimates of the thresholds indicate that these lasers could hardly be driven by compact light sources such as current electroluminescent or light-emitting diodes. Since the improvement possibilities regarding cell architecture seem to be exhausted, the advance must come from the use of new dye molecules. These molecules should show enhanced emission cross-sections and be efficiently integrable within the mesogenic solvent. In addition, the fluorescent systems must present very small quantum yields to triplet states if continuous-wave lasing is sought. In this respect, quantum dots are an alternative to explore for further investigations. Full article

(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)

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