Self-Assembly in Liquid Crystalline Materials

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

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 15833

Special Issue Editors


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Guest Editor
Department of Physics and Materials Science, University of Memphis, Memphis, TN, USA
Interests: liquid crystals; active soft matter; colloids; self-assembly

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Guest Editor
Department of Materials Science & Engineering, University of Utah, Salt Lake City, UT 84112, USA
Interests: multiscale modeling of soft-condensed matter systems; materials for energy applications
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Physics Department, University of Massachusetts, Amherst, MA 01003, USA
Interests: liquid crystal; active matter

Special Issue Information

Dear Colleagues,

Self-assembly is ubiquitous in nature, and biosystems are destined to have their own biological functions through the spontaneous assembly of molecular building blocks. Studying self-assembly will not only help us to gain a better understanding of the biological world but also shed light on designing and controlling building blocks such as DNA, fatty acid, and peptides to self-assemble into desired superstructures for bionanomaterial applications. These have attracted a great deal of interest in recent years to study self-assembly behavior in liquid crystalline materials. Thus, a whole new realm of phenomena and physics have been discovered, such as active nematics of self-assembly of non-equilibrium biological entities, programable liquid crystalline elastomers, directed micro/nanoparticles in various liquid crystalline materials, etc. It is expected that in the near future, research in self-assembly in liquid crystalline materials will find broad applications in material science, biology, and medicine.

We invite colleagues to submit papers exploring the different aspects of self-assembly in liquid crystalline materials. The potential topics include but are not limited to:

  • Directed self-assembly in liquid crystalline materials;
  • Out-of-equilibrium active nematics;
  • Microfabrication;
  • Liquid crystalline composites;
  • Multifunctional material applications;
  • Programmable liquid crystal elastomers;
  • Dynamics in liquid crystals
  • Novel liquid crystal phases (e.g. twist-bend nematic, ferroelectric nematic, etc.)

Prof. Dr. Chenhui Peng
Prof. Dr. Dmitry A. Bedrov
Prof. Dr. Shuang Zhou
Guest Editors

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Keywords

  • liquid crystals
  • active nematics
  • liquid crystal elastomer
  • active swimmer
  • colloids
  • molecular self-assembly
  • defects
  • flow pattern formation

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Published Papers (5 papers)

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Research

20 pages, 2120 KiB  
Article
2-Pyridinyl-Terminated Iminobenzoate: Type and Orientation of Mesogenic Core Effect, Geometrical DFT Investigation
by Jehan Y. Al-Humaidi, Shady Nada, Mariam Gerges, Marwa Ehab, Mariusz Jaremko, Abdul-Hamid Emwas and Mohamed Hagar
Crystals 2022, 12(7), 902; https://doi.org/10.3390/cryst12070902 - 24 Jun 2022
Cited by 3 | Viewed by 1935
Abstract
A new liquid crystal series of pyridin-2-yl 4-[4-(alkylphenyl)iminomethyl]benzoate was synthesized and characterized for their mesomorphic behavior. These compounds contain Schiff base and carboxylate ester mesogenic cores, in addition to terminal alkyl chains with a different number of carbons. The structures were confirmed via [...] Read more.
A new liquid crystal series of pyridin-2-yl 4-[4-(alkylphenyl)iminomethyl]benzoate was synthesized and characterized for their mesomorphic behavior. These compounds contain Schiff base and carboxylate ester mesogenic cores, in addition to terminal alkyl chains with a different number of carbons. The structures were confirmed via FT-IR, and 1H NMR spectroscopy. The phase transitions were studied by differential thermal analysis (DSC) and the mesophase types were identified by polarized optical microscopy (POM). A comparative study was performed between the synthesized compounds and previously reported compounds. Density functional theory (DFT) calculations were included in the study to compute the dipole moment and the polarizability, as well as the frontier molecular orbitals and the charge distribution mapping, which impact the terminal and lateral interactions of the compounds. The theoretical results were discussed to confirm the experimental data and explain the mesomorphic behavior of the compounds. Finally, the energy gap, global softness, and chemical hardness were calculated to determine the suitability of the liquid crystalline compounds to be employed in applications. Full article
(This article belongs to the Special Issue Self-Assembly in Liquid Crystalline Materials)
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9 pages, 4468 KiB  
Article
Self-Localized Liquid Crystal Micro-Droplet Arrays on Chemically Patterned Surfaces
by Jakub Kołacz and Qi-Huo Wei
Crystals 2022, 12(1), 13; https://doi.org/10.3390/cryst12010013 - 22 Dec 2021
Cited by 5 | Viewed by 3696
Abstract
Liquid crystal (LC) micro-droplet arrays are elegant systems that have a range of applications, such as chemical and biological sensing, due to a sensitivity to changes in surface properties and strong optical activity. In this work, we utilize self-assembled monolayers (SAMs) to chemically [...] Read more.
Liquid crystal (LC) micro-droplet arrays are elegant systems that have a range of applications, such as chemical and biological sensing, due to a sensitivity to changes in surface properties and strong optical activity. In this work, we utilize self-assembled monolayers (SAMs) to chemically micro-pattern surfaces with preferred regions for LC occupation. Exploiting discontinuous dewetting, dragging a drop of fluid over the patterned surfaces demonstrates a novel, high-yield method of confining LC in chemically defined regions. The broad applicability of this method is demonstrated by varying the size and LC phase of the droplets. Although the optical textures of the droplets are dictated by topological constraints, the additional SAM interface is shown to lock in inhomogeneous alignment. The surface effects are highly dependent on size, where larger droplets exhibit asymmetric director configurations in nematic droplets and highly knotted structures in cholesteric droplets. Full article
(This article belongs to the Special Issue Self-Assembly in Liquid Crystalline Materials)
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21 pages, 5206 KiB  
Article
Interplay of Active Stress and Driven Flow in Self-Assembled, Tumbling Active Nematics
by Weiqiang Wang and Rui Zhang
Crystals 2021, 11(9), 1071; https://doi.org/10.3390/cryst11091071 - 4 Sep 2021
Cited by 8 | Viewed by 2787
Abstract
Lyotropic chromonic liquid crystals (LCLCs) are a special type of hierarchical material in which self-assembled molecular aggregates are responsible for the formation of liquid crystal phases. Thanks to its unusual material properties and bio compatibility, it has found wide applications including the formation [...] Read more.
Lyotropic chromonic liquid crystals (LCLCs) are a special type of hierarchical material in which self-assembled molecular aggregates are responsible for the formation of liquid crystal phases. Thanks to its unusual material properties and bio compatibility, it has found wide applications including the formation of active nematic liquid crystals. Recent experiments have uncovered tumbling character of certain LCLCs. However, how tumbling behavior modifies structure and flow in driven and active nematics is poorly understood. Here, we rely on continuum simulation to study the interplay of extensile active stress and externally driven flow in a flow-tumbling nematic with a low twist modulus to mimic nematic LCLCs. We find that a spontaneous transverse flow can be developed in a flow-tumbling active nematic confined to a hybrid alignment cell when it is in log-rolling mode at sufficiently high activities. The orientation of the total spontaneous flow is tunable by tuning the active stress. We further show that activity can suppress pressure-driven flow of a flow-tumbling nematic in a planar-anchoring cell but can also promote a transition of the director field under a pressure gradient in a homeotropic-anchoring cell. Remarkably, we demonstrate that the frequency of unsteady director dynamics in a tumbling nematic under Couette flow is invariant against active stress when below a threshold activity but exhibits a discontinuous increase when above the threshold at which a complex, periodic spatiotemporal director pattern emerges. Taken together, our simulations reveal qualitative differences between flow-tumbling and flow-aligning active nematics and suggest potential applications of tumbling nematics in microfluidics. Full article
(This article belongs to the Special Issue Self-Assembly in Liquid Crystalline Materials)
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15 pages, 4485 KiB  
Article
Pyridine-Based Three-Ring Bent-Shape Supramolecular Hydrogen Bond-Induced Liquid Crystalline Complexes: Preparation and Density Functional Theory Investigation
by Sayed Z. Mohammady, Daifallah M. Aldhayan and Mohamed Hagar
Crystals 2021, 11(6), 628; https://doi.org/10.3390/cryst11060628 - 31 May 2021
Cited by 13 | Viewed by 3217
Abstract
A series of new supramolecular three-ring bent-shape Schiff base liquid crystal (LC) complexes were prepared and studied. On one side, two alkoxy chain lengths of the carboxylic acids were used, namely eight and sixteen carbons. Moreover, on the other side, terminal small compact [...] Read more.
A series of new supramolecular three-ring bent-shape Schiff base liquid crystal (LC) complexes were prepared and studied. On one side, two alkoxy chain lengths of the carboxylic acids were used, namely eight and sixteen carbons. Moreover, on the other side, terminal small compact groups, which substituted aniline, with different polarities were utilized. Furthermore, the hydrogen-bonding interactions in the formed complexes were elucidated by Fourier-transform infrared (FT–IR) spectroscopy. The mesomorphic thermal and optical characteristics of the samples were determined by differential thermal analysis (DSC) and polarized optical microscopy (POM). The complexes exhibited enantiotropic and dimorphic mesophase behaviors. The results indicate that the polarity of the compact groups and the lengths of the alkoxy chains greatly impacted the mesomorphic characteristics and thermal stabilities of the mesophases. The observed values of the enthalpy changes (ΔH) associated with the crystalline smectic-A (TCr-SmA) transitions were extremely small compared with the conventional values that characterize supramolecular hydrogen-bonded liquid crystalline complexes. ΔH, which corresponded to the nematic isotropic transitions (TN-I), varied from 0.13 to 9.54 kJ/mol depending mainly on the polarity of the groups that were para-attached to the aniline moiety. Finally, the theoretical results obtained by density functional theory (DFT) calculations were discussed. The DFT geometrical structures showed non-coplanar structures. The mesomorphic range was correlated with the calculated dipole moment, polarizability and the aspect ratios of the investigated compounds. Full article
(This article belongs to the Special Issue Self-Assembly in Liquid Crystalline Materials)
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14 pages, 3770 KiB  
Article
The Electro-Optical Properties and Adhesion Strength of Epoxy-Polymercaptan-Based Polymer Dispersed Liquid Crystal Films
by Gang Chen, Wei Hu, Le Zhou, Huimin Zhang, Ling Wang, Cuihong Zhang, Jian Sun, Lanying Zhang, Xiaotao Yuan and Siquan Zhu
Crystals 2021, 11(6), 576; https://doi.org/10.3390/cryst11060576 - 21 May 2021
Cited by 12 | Viewed by 2772
Abstract
Polymer dispersed liquid crystal (PDLC) films were prepared by thermal polymerization-induced phase separation in epoxy/polymercaptan/liquid crystal (LC)/accelerator mixtures. The effects of the concentration of LC and accelerator, the curing temperature, and the structure of epoxy monomer on the electro-optical (E-O) properties and adhesion [...] Read more.
Polymer dispersed liquid crystal (PDLC) films were prepared by thermal polymerization-induced phase separation in epoxy/polymercaptan/liquid crystal (LC)/accelerator mixtures. The effects of the concentration of LC and accelerator, the curing temperature, and the structure of epoxy monomer on the electro-optical (E-O) properties and adhesion strength of the PDLC films were studied systematically via E-O, peel strength, DSC, IR, and gel measurements. It showed that different polymer structures and the properties of the polymer can be obtained by changing the compositions and the curing temperature, which had significant impacts on the E-O properties of the PDLC films. Meanwhile, the polymer matrix with high glass-transition temperature (Tg) and small pore size will improve the adhesion strength of the PDLC film, and these kinds of epoxy-polymercaptan-based PDLC films have better performance than traditional acrylate-based PDLC in the aspect of the adhesion strength. This work may provide some inspiration in preparing epoxy-polymercaptan-based PDLC films, which both have excellent E-O performance and good adhesion strength, towards roll-to-roll processes and large-scale flexible applications. Full article
(This article belongs to the Special Issue Self-Assembly in Liquid Crystalline Materials)
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