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Polymeric Liquid Crystals and Applications
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Polymeric Liquid Crystals and Applications

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

Deadline for manuscript submissions: 30 September 2024 | Viewed by 11886

Special Issue Editors

Dr. Ana Catarina Trindade

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Guest Editor
CENIMAT/i3N Faculdade de Ciências e Tecnologia da Universidade NOVA de Lisboa, Lisboa Portugal and Norwegian University of Science and Technology, NTNU, Trondheim, Norway
Interests: molecular, mesoscopic (nano and micro scale) and macroscopic properties and behavior of soft materials and complex fluids, mainly liquid crystals (LCs) and cellulose-based systems (CBS); organic synthesis of liquid crystals and cellulose derivatives; preparation of micro and nano-membranes/wires/structures from liquid crystalline solutions to originate high-added value materials; modification, preparation and characterization of cellulose micro/nano rods; study of self-assembling, defects and photonic properties of LCs as well as CBS and cellulose nano rods
Dr. João Canejo

E-Mail Website
Guest Editor
CENIMAT/i3N FCT/NOVA, Portugal
Interests: liquid crystals; cellulosic liquid crystalline phases; cellulose-based materials; production of non-woven membranes using electrospinning; mechanical characterization of materials; morphological characterization of materials using scanning electron microscopy (SEM)
Prof. Dr. Pedro De Almeida

E-Mail Website
Guest Editor
1. Physics Department, Lisbon Superior Institute of Engineering, Rua Conselheiro Emídio Navarro, 1, 1959-007 Lisboa, Portugal
2. i3N, CENIMAT, Materials Science Department, Faculty of Sciences and Technology, NOVA University of Lisbon, Campus da Caparica, 2829-516 Caparica, Portugal
Interests: liquid crystals; liquid crystals applications; polymeric materials; liquid crystalline polymers; cellulosic materials and derivatives; cellulosic liquid crystals; solid state NMR; Rheo-NMR; electro-optical properties; anisotropic mechanical properties; mechano-optical properties
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymeric liquid crystal systems (LCPs) show the anisotropic characteristic of liquid crystals, and, at the same time, demonstrate many of the useful and versatile properties of polymers. These systems present a great variety of chemical and structural properties with potential benefits of programmed and superior material properties, thereby providing more convenient polymer processing and smart responses to different stimuli. Polymeric liquid crystals have been investigated for several decades in different research applications, with the aim of using them in numerous commercial applications.

With this Special Issue of Molecules, we aim to bring together pure and applied research papers on LCPs, including their applications. Presenting a very broad scope, this Special Issue welcomes full papers, short communications and review articles on polymer design, modelling, and synthesis, and those devoted to structure/processing/properties and applications of liquid crystalline polymers. Studies on main-chain and side-chain LCPs or polymer liquid crystalline blends, dispersions, and encapsulations and biological and bio-inspired liquid crystals are also welcome.

Dr. Ana Catarina Trindade
Dr. João Canejo
Prof. Pedro Marques de Almeida
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

  • phases, structures and ordering
  • self-assembly, colloids
  • instabilities, pattern formation and chaos, fibers
  • biological and bio-inspired liquid crystals
  • polymer-liquid crystal blends
  • conductive liquid crystals
  • switchable polymers
  • nanostructured systems, supramolecules
  • polymers, elastomers and gels
  • photosensitive liquid crystals
  • confined liquid crystals
  • molecular design, synthesis and new materials
  • sensors
  • actuators
  • O-LED and polymer LCD devices
  • conducting polymer liquid crystals
  • ferroelectrics
  • biopolymer liquid crystals
  • drug delivery
  • mathematical modelling, symmetry and topology
  • novel applications of liquid crystalline systems

Published Papers (7 papers)

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Research

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16 pages, 16099 KiB  
Article
Preparation and Characterization of Bilayer Polymer-Dispersed Liquid Crystals Doped with Gd2O3 Nanoparticles and Rhodamine B Base Fluorescent Dye
by Yongle Wu, Yuzhen Zhao, Xun Li, Hong Gao, Zhun Guo, Dong Wang, Yi Luan and Lei Wang
Molecules 2024, 29(5), 1126; https://doi.org/10.3390/molecules29051126 - 02 Mar 2024
Viewed by 490
Abstract
Using the polymerization-induced phase separation (PIPS) method, bilayer polymer-dispersed liquid crystal (PDLC) films with a PDLC-PVA-PDLC structure were prepared in this work. It was found that all PDLC performance indexes were affected by polymer mesh size after comparing the microscopic morphology and electro-optical [...] Read more.
Using the polymerization-induced phase separation (PIPS) method, bilayer polymer-dispersed liquid crystal (PDLC) films with a PDLC-PVA-PDLC structure were prepared in this work. It was found that all PDLC performance indexes were affected by polymer mesh size after comparing the microscopic morphology and electro-optical properties of samples with different monomer ratios. Gd2O3 nanoparticles and rhodamine B base fluorescent dyes introduced into the bilayer PDLC optimized the samples’ electro-optical properties and developed new functionalities. In addition, the bilayer PDLC doped with Gd2O3 and rhodamine B base held excellent progressive driving functions as well as stable durability properties. Samples doped with Gd2O3 nanoparticles and rhodamine B base also produced excellent anti-counterfeiting effects under UV irradiation at different angles, further exploiting the application potential of PDLC. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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8 pages, 3307 KiB  
Communication
Polymer Dispersed Liquid Crystal Imprinted by Microlens Array for Enhanced Outcoupling Efficiency of Organic Light Emitting Diode
by Seongmin Lim, Hyeon-Sik Ahn, Eun-Jeong Jang, So-Young Boo, Akpeko Gasonoo, Jin-Seog Gwag, Jae-Hyun Lee and Yoonseuk Choi
Molecules 2024, 29(1), 73; https://doi.org/10.3390/molecules29010073 - 22 Dec 2023
Viewed by 651
Abstract
In this paper, we demonstrate the use of polymer dispersed liquid crystal (PDLC) imprinted with a microlens array (MLA) via solution process to improve the outcoupling efficiency of organic light emitting diodes (OLEDs). The PDLC, well known for its scattering effect, is an [...] Read more.
In this paper, we demonstrate the use of polymer dispersed liquid crystal (PDLC) imprinted with a microlens array (MLA) via solution process to improve the outcoupling efficiency of organic light emitting diodes (OLEDs). The PDLC, well known for its scattering effect, is an excellent technology for improving the outcoupling efficiency of OLEDs. Additionally, we introduce a simple spin-coating process to fabricate PDLC which is adaptable for future solution-processed OLEDs. The MLA-imprinted PDLC applied OLED shows an enhancement factor of 1.22 in outcoupling efficiency which is a 37.5% increase compared to the existing PDLC techniques without changing the electrical properties of the OLED. Through this approach, we can expect the roll-to-roll based extremely flexible OLED, and with further research on pattering PDLC by various templates, higher outcoupling efficiency is achievable through a simple UV irradiation process. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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10 pages, 2639 KiB  
Article
Confinement-Induced Fabrication of Liquid Crystalline Polymeric Fibers
by Jae Gwang Kim, Jae Gyeong Lee and Jeong Jae Wie
Molecules 2022, 27(17), 5639; https://doi.org/10.3390/molecules27175639 - 01 Sep 2022
Cited by 1 | Viewed by 1450
Abstract
In aqueous media, liquid crystalline droplets typically form spherical shapes in order to minimize surface energy. Recently, non-spherical geometry has been reported using molecular self-assembly of surfactant-stabilized liquid crystalline oligomers, resulting in branched and randomly oriented filamentous networks. In this study, we report [...] Read more.
In aqueous media, liquid crystalline droplets typically form spherical shapes in order to minimize surface energy. Recently, non-spherical geometry has been reported using molecular self-assembly of surfactant-stabilized liquid crystalline oligomers, resulting in branched and randomly oriented filamentous networks. In this study, we report a polymerization of liquid crystalline polymeric fibers within a micro-mold. When liquid crystal oligomers are polymerized in freely suspended aqueous media, curvilinear and randomly networked filaments are obtained. When reactive liquid crystalline monomers are oligomerized in a micro-channel, however, highly aligned linear fibers are polymerized. Within a top-down microfabricated mold, a bottom-up molecular assembly was successfully achieved in a controlled manner by micro-confinement, suggesting a unique opportunity for the programming architecture of materials via a hybrid approach. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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19 pages, 7146 KiB  
Article
Three Rings Schiff Base Ester Liquid Crystals: Experimental and Computational Approaches of Mesogenic Core Orientation Effect, Heterocycle Impact
by Shady Nada, Mohamed Hagar, Omaima Farahat, Ahmed A. Hasanein, Abdul-Hamid Emwas, Abeer Ali Sharfalddin, Mariusz Jaremko and Mohamed A. Zakaria
Molecules 2022, 27(7), 2304; https://doi.org/10.3390/molecules27072304 - 01 Apr 2022
Cited by 7 | Viewed by 1860
Abstract
Three rings 2-hydroxypyridine liquid crystalline compounds have been prepared and fully characterized. The mesomorphic behavior of the prepared compounds has been investigated in terms of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Moreover, a comparative study between the prepared compounds and [...] Read more.
Three rings 2-hydroxypyridine liquid crystalline compounds have been prepared and fully characterized. The mesomorphic behavior of the prepared compounds has been investigated in terms of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Moreover, a comparative study between the prepared compounds and previously reported analogs has been discussed in terms of the orientation and position of the mesogenic core, in addition to the direction of the terminal alkyl chains. Furthermore, a detailed computational approach has been studied to illustrate the effect of geometrical and dimensional parameters on the type of the enhanced texture and the mesomorphic range and stability. The results of the DFT study revealed that the orientation of the mesogen could affect the mesomorphic behavior and this has been attributed in terms of the degree of the polarizability of the linking groups. This result has been confirmed by calculation of the net dipole moment and the molecular electrostatic potential that show how the mesogen orientation and position could impact the molecular charge separation. Finally, the effect of the pyridyl group has been also investigated in terms of the calculated aromaticity index and the π-π stacking. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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13 pages, 3877 KiB  
Article
Alcohol Selective Optical Sensor Based on Porous Cholesteric Liquid Crystal Polymer Networks
by Tai-Yuan Yeh, Ming-Fu Liu, Ru-De Lin and Shug-June Hwang
Molecules 2022, 27(3), 773; https://doi.org/10.3390/molecules27030773 - 25 Jan 2022
Cited by 6 | Viewed by 1911
Abstract
A responsive hydrogen-bonded cholesteric liquid crystal polymer (CLCP) film with controlled porosity was fabricated as an optical sensor to distinguish between methanol and ethanol in alcohol solutions. To facilitate responding the alcohols, porosity was generated by removing the nonreactive liquid crystal agent, and [...] Read more.
A responsive hydrogen-bonded cholesteric liquid crystal polymer (CLCP) film with controlled porosity was fabricated as an optical sensor to distinguish between methanol and ethanol in alcohol solutions. To facilitate responding the alcohols, porosity was generated by removing the nonreactive liquid crystal agent, and the hydrogen bridges of CLCP were broken. The sensitivities of CLCPs to ethanol and methanol were obtained by monitoring the wavelength shifts of the transmission spectrum at different alcohol concentrations and ratios of methanol/ethanol. Changes in the central wavelength of the CLCP network transmission spectrum allowed the methanol–ethanol ratio to be discriminated. A linear relationship between wavelength shift of CLCP networks and alcohol concentration was obtained experimentally, and the sensor characteristics were explored. The sensitivities of the CLCPs were 1.35 and 0.18 nm/% to ethanol and methanol, respectively. The sensing sensitivity of cholesteric networks to alcohol molecules increased as the methanol–ethanol ratio declined. Therefore, CLCP could act as a stimuli-responsive material to distinguish the concentrations of acetone and ethanol in mixed solutions. Furthermore, the impact of UV intensity for curing a CLC mixture on the sensing sensitivity to the different alcohol concentrations was also studied. The higher UV intensity could enhance the sensitivity to alcohol molecules and distinguishing ability between methanol and ethanol. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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29 pages, 2582 KiB  
Article
Influence of Liquid Crystallinity and Mechanical Deformation on the Molecular Relaxations of an Auxetic Liquid Crystal Elastomer
by Thomas Raistrick, Matthew Reynolds, Helen F. Gleeson and Johan Mattsson
Molecules 2021, 26(23), 7313; https://doi.org/10.3390/molecules26237313 - 02 Dec 2021
Cited by 5 | Viewed by 1993
Abstract
Liquid Crystal Elastomers (LCEs) combine the anisotropic ordering of liquid crystals with the elastic properties of elastomers, providing unique physical properties, such as stimuli responsiveness and a recently discovered molecular auxetic response. Here, we determine how the molecular relaxation dynamics in an acrylate [...] Read more.
Liquid Crystal Elastomers (LCEs) combine the anisotropic ordering of liquid crystals with the elastic properties of elastomers, providing unique physical properties, such as stimuli responsiveness and a recently discovered molecular auxetic response. Here, we determine how the molecular relaxation dynamics in an acrylate LCE are affected by its phase using broadband dielectric relaxation spectroscopy, calorimetry and rheology. Our LCE is an excellent model system since it exhibits a molecular auxetic response in its nematic state, and chemically identical nematic or isotropic samples can be prepared by cross-linking. We find that the glass transition temperatures (Tg) and dynamic fragilities are similar in both phases, and the T-dependence of the α relaxation shows a crossover at the same T* for both phases. However, for T>T*, the behavior becomes Arrhenius for the nematic LCE, but only more Arrhenius-like for the isotropic sample. We provide evidence that the latter behavior is related to the existence of pre-transitional nematic fluctuations in the isotropic LCE, which are locked in by polymerization. The role of applied strain on the relaxation dynamics and mechanical response of the LCE is investigated; this is particularly important since the molecular auxetic response is linked to a mechanical Fréedericksz transition that is not fully understood. We demonstrate that the complex Young’s modulus and the α relaxation time remain relatively unchanged for small deformations, whereas for strains for which the auxetic response is achieved, significant increases are observed. We suggest that the observed molecular auxetic response is coupled to the strain-induced out-of-plane rotation of the mesogen units, in turn driven by the increasing constraints on polymer configurations, as reflected in increasing elastic moduli and α relaxation times; this is consistent with our recent results showing that the auxetic response coincides with the emergence of biaxial order. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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Review

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24 pages, 2054 KiB  
Review
Supramolecular Aggregates: Hardness Plus Softness
by Lia Queiroz do Amaral
Molecules 2021, 26(14), 4233; https://doi.org/10.3390/molecules26144233 - 12 Jul 2021
Viewed by 2164
Abstract
The properties of supramolecular aggregates cross several disciplines, embracing the sciences of nature and joining theory, experiment, and application. There are few articles centering on the problems of interdisciplinarity, and this paper gives an alternative approach, starting with scientific divulgation, bringing concepts from [...] Read more.
The properties of supramolecular aggregates cross several disciplines, embracing the sciences of nature and joining theory, experiment, and application. There are few articles centering on the problems of interdisciplinarity, and this paper gives an alternative approach, starting with scientific divulgation, bringing concepts from their origin, to facilitate the access of young scientists to the scientific content. Didactic examples are taken from the experience of the author in changing directions of research due to several circumstances of life (including maternity), starting from the view of a rigorous student of physics and evolving to several subjects in chemistry. The scientific part starts with concepts related to nuclear interactions, using the technique of neutron scattering in reactors, and evolves to research in molecular physics. Finally, it arrives at the academic context, with research in condensed matter physics, with X-ray and other techniques, starting with detergents forming nematic lyotropic liquid crystals and the phase transition sequence of isotropic to nematics to hexagonal. The scientific subjects evolved to biological and bio-inspired liquid crystals, including DNA and also specific lipids and phospholipids in biomimetic membranes. Special attention is given to the question of distribution of matter in these complex systems and the non-trivial connections between biochemistry, structures, auto-aggregation, and biology. Full article
(This article belongs to the Special Issue Polymeric Liquid Crystals and Applications)
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