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Nanomaterials
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Current Research in Nematic Liquid Crystal Nanocomposites
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Current Research in Nematic Liquid Crystal Nanocomposites

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanocomposite Materials".

Deadline for manuscript submissions: 20 August 2024 | Viewed by 3048

Special Issue Editors

Dr. Lelidis Ioannis

E-Mail Website
Guest Editor
Faculty of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, 15784 Athens, Greece
Interests: liquid crystals; nanocomposites; phase transitions; elasticity; instabilities; electrolytes; wetting
Prof. Dr. Samo Kralj

E-Mail Website
Guest Editor
1. Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska 160, 2000 Maribor, Slovenia
2. Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Interests: liquid crystals; nanocomposites; phase transitions; instabilities; wetting; topological defects
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Liquid crystals (LCs) combine the fluidity of ordinary liquids with the long-range order of crystalline matter. This combination gives rise to the high responsiveness of LCs at external fields/stimuli (electric and magnetic field, light, mechanical stress, chemical environment, etc.) which are at the origin of most LCs’ applications and devices. In recent decades, an important activity in thermotropic and lyotropic liquid crystalline materials has been the investigation of nanoparticles’ impact in LC hosts. Of particular interest is the discovery of effective materials exhibiting anomalously large responses or qualitatively new features. This research field is continuously enlarged and diversified both because new liquid crystalline phases have been discovered and because a large variety of novel nanoparticle types have been synthesized.

This Special Issue will present comprehensive research outlining progress on the impact of nanoparticles in liquid crystal physics, the emergence of new properties at the nanocomposite systems, and improvements in the performance of liquid crystal devices, as well as the invention of new kinds of applications and devices. This also includes the major problem of dispersion stability, surface activation, the use of a liquid crystal host to order nanoparticles, and theoretical description and simulations of nanocomposite systems. We invite authors to contribute original research articles and review articles covering current progress on liquid crystal nanocomposites.

Dr. Lelidis Ioannis
Prof. Dr. Samo Kralj
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. Nanomaterials 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 2900 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

  • nanocomposites
  • liquid crystals
  • nanoparticles
  • dispersion stabilization
  • nanoparticle organization
  • order
  • surface functionalization
  • topological defects
  • theory and simulations
  • characterization and experimental methods
  • applications and devices

Published Papers (4 papers)

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Research

25 pages, 5809 KiB  
Article
The Dominance of Pretransitional Effects in Liquid Crystal-Based Nanocolloids: Nematogenic 4-methoxybenzylidene-4′–butylaniline with Transverse Permanent Dipole Moment and BaTiO3 Nanoparticles
by Aleksandra Drozd-Rzoska, Joanna Łoś and Sylwester J. Rzoska
Nanomaterials 2024, 14(8), 655; https://0-doi-org.brum.beds.ac.uk/10.3390/nano14080655 - 09 Apr 2024
Viewed by 364
Abstract
The report presents static, low-frequency, and dynamic dielectric properties in the isotropic liquid, nematic, and solid phases of MBBA and related nanocolloids with paraelectric BaTiO3 nanoparticles (spherical, d = 50 nm). MBBA (4-methoxybenzylidene-4′–butylaniline) is a liquid crystalline compound with a permanent dipole [...] Read more.
The report presents static, low-frequency, and dynamic dielectric properties in the isotropic liquid, nematic, and solid phases of MBBA and related nanocolloids with paraelectric BaTiO3 nanoparticles (spherical, d = 50 nm). MBBA (4-methoxybenzylidene-4′–butylaniline) is a liquid crystalline compound with a permanent dipole moment transverse to the long molecular axis. The distortions-sensitive analysis of the dielectric constant revealed its hidden pretransitional anomaly, strongly influenced by the addition of nanoparticles. The evolution of the dielectric constant in the nematic phase shows the split into two regions, with the crossover coinciding with the standard melting temperature. The ‘universal’ exponential-type behavior of the low-frequency contribution to the real part of the dielectric permittivity is found. The critical-like pretransitional behavior in the solid phase is also evidenced. This is explained by linking the Lipovsky model to the Mossotti catastrophe concept under quasi-negative pressure conditions. The explicit preference for the ‘critical-like’ evolution of the apparent activation enthalpy is worth stressing for dynamics. Finally, the long-range, ‘critical-like’ behavior of the dissipation factor (D = tgδ), covering the isotropic liquid and nematic phases, is shown. Full article
(This article belongs to the Special Issue Current Research in Nematic Liquid Crystal Nanocomposites)
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10 pages, 4193 KiB  
Article
Criticality Controlling Mechanisms in Nematic Liquid Crystals
by Maha Zid, George Cordoyiannis, Zdravko Kutnjak and Samo Kralj
Nanomaterials 2024, 14(3), 320; https://0-doi-org.brum.beds.ac.uk/10.3390/nano14030320 - 05 Feb 2024
Cited by 1 | Viewed by 730
Abstract
We theoretically study the generic mechanisms that could establish critical behavior in nematic liquid crystals (NLCs). The corresponding free energy density terms should exhibit linear coupling with the nematic order parameter and, via this coupling, enhance the nematic order. We consider both temperature- [...] Read more.
We theoretically study the generic mechanisms that could establish critical behavior in nematic liquid crystals (NLCs). The corresponding free energy density terms should exhibit linear coupling with the nematic order parameter and, via this coupling, enhance the nematic order. We consider both temperature- and pressure-driven, order–disorder phase transitions. We derive a scaled effective free energy expression that describes how qualitatively different mechanisms enforce critical behavior. Our main focus is on the impact of nanoparticles (NPs) in homogeneous NP-NLC mixtures. We illustrate that in the case of pressure-driven phase changes, lower concentrations are needed to impose critical point conditions in comparison with pure temperature variations. Full article
(This article belongs to the Special Issue Current Research in Nematic Liquid Crystal Nanocomposites)
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14 pages, 4694 KiB  
Article
Biaxial Structures of Localized Deformations and Line-like Distortions in Effectively 2D Nematic Films
by Luka Mesarec, Samo Kralj and Aleš Iglič
Nanomaterials 2024, 14(3), 246; https://0-doi-org.brum.beds.ac.uk/10.3390/nano14030246 - 23 Jan 2024
Viewed by 811
Abstract
We numerically studied localized elastic distortions in curved, effectively two-dimensional nematic shells. We used a mesoscopic Landau-de Gennes-type approach, in which the orientational order is theoretically considered by introducing the appropriate tensor nematic order parameter, while the three-dimensional shell shape is described by [...] Read more.
We numerically studied localized elastic distortions in curved, effectively two-dimensional nematic shells. We used a mesoscopic Landau-de Gennes-type approach, in which the orientational order is theoretically considered by introducing the appropriate tensor nematic order parameter, while the three-dimensional shell shape is described by the curvature tensor. We limited our theoretical consideration to axially symmetric shapes of nematic shells. It was shown that in the surface regions of stomatocyte-class nematic shell shapes with large enough magnitudes of extrinsic (deviatoric) curvature, the direction of the in-plane orientational ordering can be mutually perpendicular above and below the narrow neck region. We demonstrate that such line-like nematic distortion configurations may run along the parallels (i.e., along the circular lines of constant latitude) located in the narrow neck regions of stomatocyte-like nematic shells. It was shown that nematic distortions are enabled by the order reconstruction mechanism. We propose that the regions of nematic shells that are strongly elastically deformed, i.e., topological defects and line-like distortions, may attract appropriately surface-decorated nanoparticles (NPs), which could potentially be useful for the controlled assembly of NPs. Full article
(This article belongs to the Special Issue Current Research in Nematic Liquid Crystal Nanocomposites)
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14 pages, 1616 KiB  
Article
Exploring Quantum Dots Size Impact at Phase Diagram and Electrooptical Properties in 8CB Liquid Crystal Soft-Nanocomposites
by Stefanos Basim Atata and Ioannis Lelidis
Nanomaterials 2023, 13(22), 2980; https://0-doi-org.brum.beds.ac.uk/10.3390/nano13222980 - 20 Nov 2023
Viewed by 689
Abstract
We explore the influence of functionalized core–shell CdSe/ZnS quantum dots on the properties of the host liquid crystal compound 4-cyano-4′-octylbiphenyl (8CB) through electrooptical measurements. Two different diameters of quantum dots are used to investigate the size effects. We assess both the dispersion quality [...] Read more.
We explore the influence of functionalized core–shell CdSe/ZnS quantum dots on the properties of the host liquid crystal compound 4-cyano-4′-octylbiphenyl (8CB) through electrooptical measurements. Two different diameters of quantum dots are used to investigate the size effects. We assess both the dispersion quality of the nanoparticles within the mixtures and the phase stability of the resulting anisotropic soft nanocomposites using polarizing optical microscopy. The temperature-mass fraction phase diagrams of the nanocomposites reveal deviations from the linear behavior in the phase stability lines. We measure the birefringence, the threshold voltage of the Fréedericksz transition, and the electrooptic switching times of the nanocomposite systems in planar cell geometry as functions of temperature, mass fraction, and diameter of the quantum dots. Beyond a critical mass fraction of the dopant nanoparticles, the nematic order is strongly reduced. Furthermore, we investigate the impact of the nanoparticle size and mass fraction on the viscoelastic coefficient. The anchoring energy at the interfaces of the liquid crystal with the cell and the quantum dots is estimated. Full article
(This article belongs to the Special Issue Current Research in Nematic Liquid Crystal Nanocomposites)
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