Special Issue "Liquid Crystal Thin Films: Structures and Applications"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Chemical and Molecular Sciences".

Deadline for manuscript submissions: 30 August 2022 | Viewed by 2854

Special Issue Editor

Dr. Mohamed Amine Gharbi
E-Mail Website
Guest Editor
Department of Physics, University of Massachusetts Boston, Boston, MA 02125, USA
Interests: active soft matter; liquid crystals; directed self-assembly; interfacial phenomena; functional nanomaterials; biomaterials

Special Issue Information

Dear Colleagues,

Soft materials, in particular liquid crystals, assemble and reconfigure in response to external constraints. They provide a model system for fundamental physics questions and the development of novel applications. Investigating the properties of liquid crystal films can lead to the development of new means to control the assembly of colloidal objects, including functional nanomaterials, biomaterials, and active matter.  A better understanding of how these films behave when confined under particular conditions will provide a fascinating tool for the creation of a new generation of advanced materials that may respond to external conditions.

This issue highlights the properties of liquid crystal films and emphasizes their role in the development of novel applications. We are inviting submissions exploring the latest advances in studying the properties of liquid crystal films, including bulk and surface properties that can lead to potential applications in the future. In particular, we encourage the submission of papers investigating a broad range of liquid crystal mesophases. Reviews that succinctly analyze recent progress in the field will also be considered.

Dr. Mohamed Amine Gharbi 
Guest Editor

Manuscript Submission Information

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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. Applied Sciences 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 2300 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

  • confinement
  • thin films
  • interfaces
  • directed assembly
  • liquid crystal devices

Published Papers (3 papers)

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Research

Article
Orientation of Liquid Crystalline Molecules on PDMS Surfaces and within PDMS Microfluidic Systems
Appl. Sci. 2021, 11(24), 11593; https://doi.org/10.3390/app112411593 - 07 Dec 2021
Cited by 1 | Viewed by 461
Abstract
The unique components of PDMS-based microfluidic systems are those combined with liquid crystalline materials. Their functionality, especially when it comes to optical applications, highly depends on the LC molecular arrangement. This work summarizes experimental investigations on the orientation of molecules within LC:PDMS structures [...] Read more.
The unique components of PDMS-based microfluidic systems are those combined with liquid crystalline materials. Their functionality, especially when it comes to optical applications, highly depends on the LC molecular arrangement. This work summarizes experimental investigations on the orientation of molecules within LC:PDMS structures according to the manufacturing technologies. The availability of high-quality molds to pattern PDMS is a significant barrier to the creation of advanced microfluidic systems. The possibility of using inexpensive molds in the rapid and reproducible fabrication process has been particularly examined as an alternative to photolithography. Different geometries, including an innovative approach for the electrical control of the molecular arrangement within PDMS microchannels, are presented. These studies are critical for novel optofluidic systems, introducing further research on LC:PDMS waveguiding structures. Full article
(This article belongs to the Special Issue Liquid Crystal Thin Films: Structures and Applications)
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Article
Comment on the Determination of the Polar Anchoring Energy by Capacitance Measurements in Nematic Liquid Crystals
Appl. Sci. 2021, 11(16), 7387; https://doi.org/10.3390/app11167387 - 11 Aug 2021
Viewed by 536
Abstract
Capacitance measurements have been extensively used to measure the anchoring extrapolation length L at a nematic–substrate interface. These measurements are extremely delicate because the value found for L often critically depends on the sample thickness and the voltage range chosen to perform the [...] Read more.
Capacitance measurements have been extensively used to measure the anchoring extrapolation length L at a nematic–substrate interface. These measurements are extremely delicate because the value found for L often critically depends on the sample thickness and the voltage range chosen to perform the measurements. Several reasons have been proposed to explain this observation, such as the presence of inhomogeneities in the director distribution on the bounding plates or the variation with the electric field of the dielectric constants. In this paper, I propose a new method to measure L that takes into account this second effect. This method is more general than the one proposed in Murauski et al. Phys. Rev. E 71, 061707 (2005) because it does not assume that the anchoring angle is small and that the anchoring energy is of the Rapini–Papoular form. This method is applied to a cell of 8CB that is treated for planar unidirectional anchoring by photoalignment with the azobenzene dye Brilliant Yellow. The role of flexoelectric effects and the shape of the anchoring potential are discussed. Full article
(This article belongs to the Special Issue Liquid Crystal Thin Films: Structures and Applications)
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Article
Environmentally Stable Chiral-Nematic Liquid-Crystal Elastomers with Mechano-Optical Properties
Appl. Sci. 2021, 11(11), 5037; https://doi.org/10.3390/app11115037 - 29 May 2021
Cited by 2 | Viewed by 1142
Abstract
Chiral-nematic liquid crystal (N* LC) elastomers exhibit mechano-optical responsive behavior. However, practical sensor applications have been limited by the intrinsic sensitivity of N* LC elastomers to environmental conditions, such as temperature. Although densely cross-linked LC network polymers exhibit high thermal stability, they are [...] Read more.
Chiral-nematic liquid crystal (N* LC) elastomers exhibit mechano-optical responsive behavior. However, practical sensor applications have been limited by the intrinsic sensitivity of N* LC elastomers to environmental conditions, such as temperature. Although densely cross-linked LC network polymers exhibit high thermal stability, they are not proper for the mechanical sensor due to high glass transition temperatures and low flexibility. To overcome these issues, we focused on enhancing thermal stability by introducing noncovalent cross-linking sites via intermolecular interactions between LC molecules bonded to the polymer network. N* LC elastomers with a cyanobiphenyl derivative as a side-chain mesogen exhibited mechano-optical responsive behavior, with a hypsochromic shift of the reflection peak wavelength under an applied tensile strain and quick shape and color recovery owing to high elasticity. Notably, the N* LC elastomers showed high resistance to harsh environments, including high temperatures and various solvents. Interactions, such as π–π stacking and dipole–dipole interactions, between the cyanobiphenyl units can act as weak cross-links, thus improving the thermal stability of the LC phase without affecting the mechano-optical response. Thus, these N* LC elastomers have great potential for the realization of practical mechano-optical sensors. Full article
(This article belongs to the Special Issue Liquid Crystal Thin Films: Structures and Applications)
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