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Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to...
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Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 15470

Special Issue Editors

Prof. Dr. Paola Astolfi

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Guest Editor
Dipartimento SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
Interests: drug delivery; lyotropic liquid crystals; colloidal nanoparticles; structural characterization by spectroscopic techniques, polymers for wastewater treatment
Prof. Dr. Michela Pisani

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Guest Editor
Dipartimento SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
Interests: liquid crystalline structures; lipid-based systems in gene and drug delivery; Liposomes; cubosomes and hexosomes dispersions; x-ray structural characterization
Prof. Dr. Francesco Vita

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Guest Editor
Dipartimento SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
Interests: liquid crystals; soft materials; X-ray diffraction; thin films; optical materials

Special Issue Information

Dear Colleagues,

Liquid crystals are fascinating soft materials characterized by the ability to self-assemble into a variety of supramolecular structures featuring a degree of ordering intermediate between that of crystalline solids and liquids. It is this complex structural organization, and its sensitivity to external stimuli, that determines the peculiar macroscopic properties of liquid crystals and makes them play a pivotal role in the most diverse fields, from electro-optics to nanomedicine, from functional materials to polymer technology.

Open to original research papers and reviews, this issue aims to highlight recent developments and novel trends in the nano-structural investigation of liquid crystals, focusing on both fundamental aspects and their technological potential. Suitable topics include, but are not limited to: the structural characterization of nanoscale liquid crystal order; its computational simulation and theoretical modelling; mesophases with unconventional supramolecular morphologies; surface properties, thin films and confined liquid crystals; hybrid, colloidal and nano-composite liquid crystalline materials; liquid crystalline nanostructures; biological and biomimetic liquid crystals.

Prof. Dr. Paola Astolfi
Prof. Dr. Michela Pisani
Prof. Dr. Francesco Vita
Guest Editors

Manuscript Submission Information

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Keywords

  • Thermotropic liquid crystals
  • Lyotropic liquid crystals
  • Self-assembly
  • X-ray diffraction
  • Nanostructured liquid crystals
  • Functional materials
  • Nanotechnology

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Published Papers (7 papers)

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Research

Jump to: Review

16 pages, 7768 KiB  
Article
The Rainbow Arching over the Fluorescent Thienoviologen Mesophases
by Giuseppina Anna Corrente, Giuseppe Di Maio, Massimo La Deda, Odda Ruiz de Ballesteros, Bartolo Gabriele, Lucia Veltri, Finizia Auriemma and Amerigo Beneduci
Nanomaterials 2022, 12(23), 4284; https://doi.org/10.3390/nano12234284 - 1 Dec 2022
Cited by 1 | Viewed by 1371
Abstract
Thermofluorochromic materials exhibit tunable fluorescence emission on heating or cooling. They are highly desirable for applications ranging from temperature sensing to high-security anti-counterfeiting. Luminescent matrices based on liquid crystals are very promising, particularly those based on liquid crystals with intrinsic fluorescence. However, only [...] Read more.
Thermofluorochromic materials exhibit tunable fluorescence emission on heating or cooling. They are highly desirable for applications ranging from temperature sensing to high-security anti-counterfeiting. Luminescent matrices based on liquid crystals are very promising, particularly those based on liquid crystals with intrinsic fluorescence. However, only a few examples have been reported, suggesting ample margins for development in the field, due to the wide range of fluorophores and supramolecular organizations to be explored. Moreover, thermofluorochromic liquid crystals can be tailored with further functionalities to afford multi-stimuli responsive materials. For the first time, herein we report the thermofluorochromism of thienoviologen liquid crystals, already known to show bulk electrochromism and electrofluorochromism. In particular, we studied their photophysics in the 25 °C–220 °C range and as a function of the length of the N-linear alkyl chains, m (9 ≤ m ≤ 12 C atoms), and the type of anion, X (X = OTs-, OTf-, BF4-, NTf2-). Interestingly, by changing the parameters m, X and T, their fluorescence can be finely tuned in the whole visible spectral range up to the NIR, by switching among different mesophases. Importantly, by fixing the structural parameters m and X, an interesting thermofluorochromism can be achieved for each thienoviologen in a homologous series, leading to a switch of the emitted light from red to green and from white to blue as a consequence of the temperature-induced variation in the supramolecular interactions in the self-assembled phases. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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10 pages, 1688 KiB  
Article
Nanoscale Structure of Langmuir–Blodgett Film of Bent-Core Molecules
by Fabrizio Corrado Adamo, Federica Ciuchi, Maria Penelope De Santo, Paola Astolfi, Isabelle Warner, Eric Scharrer, Michela Pisani, Francesco Vita and Oriano Francescangeli
Nanomaterials 2022, 12(13), 2285; https://doi.org/10.3390/nano12132285 - 2 Jul 2022
Cited by 3 | Viewed by 1889
Abstract
Bent-core mesogens (BCMs) are a class of thermotropic liquid crystals featuring several unconventional properties. However, the interpretation and technological exploitation of their unique behavior have been hampered by the difficulty of controlling their anchoring at surfaces. To tackle this issue, we report the [...] Read more.
Bent-core mesogens (BCMs) are a class of thermotropic liquid crystals featuring several unconventional properties. However, the interpretation and technological exploitation of their unique behavior have been hampered by the difficulty of controlling their anchoring at surfaces. To tackle this issue, we report the nanoscale structural characterization of BCM films prepared using the Langmuir–Blodgett technique. Even though BCMs are quite different from typical amphiphilic molecules, we demonstrate that stable molecular films form over water, which can then be transferred onto silicon substrates. The combination of Brewster angle microscopy, atomic force microscopy, and X-ray reflectivity measurements shows that the molecules, once transferred onto a solid substrate, form a bilayer structure with a bottom layer of flat molecules and an upper layer of upright molecules. These results suggest that Langmuir–Blodgett films of BCMs can provide a useful means to control the alignment of this class of liquid crystals. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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11 pages, 7641 KiB  
Article
Spherical Confinement of Chromonics: Effects of a Chiral Aminoacid
by Lorenza Spina, Federica Ciuchi, Caterina Maria Tone, Riccardo Barberi and Maria Penelope De Santo
Nanomaterials 2022, 12(4), 619; https://doi.org/10.3390/nano12040619 - 12 Feb 2022
Cited by 4 | Viewed by 2060
Abstract
Induced or spontaneous chirality in natural systems is an intriguing issue. In recent years, a lot of attention has been focused on chirality of chromonic liquid crystals, a class of materials that is able to self-assemble in columnar structures. However, the mechanism involved [...] Read more.
Induced or spontaneous chirality in natural systems is an intriguing issue. In recent years, a lot of attention has been focused on chirality of chromonic liquid crystals, a class of materials that is able to self-assemble in columnar structures. However, the mechanism involved in the arising of chirality in these materials, that starts at the molecular level and controls the supramolecular structure, is poorly understood; however, it is certainly affected by ionic strength. In this work we present the results obtained doping Cromolyn, a chromonic material, with a strong helical-twisting-power peptide, and confining it in a spherical geometry. We demonstrate, by means of optical polarized microscopy and structural analysis, that both the geometrical constraint and the presence of the chiral dopant enhance the chiral effect; we also demonstrate that they favor the rise of a highly ordered helical superstructure, that may be optimized upon adding an ionic dye to the system. Finally, we report a procedure for the preparation of free-standing polymeric films, embedding and preserving the microspheres, and paving the way for the creation of biocompatible and eco-friendly optical devices to be used in the sensor and anticounterfeiting fields. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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15 pages, 3486 KiB  
Article
Converting non-Mesogenic to Mesogenic Stacking of Amino-s-Triazine-Based Dendrons with p-CN Phenyl Unit by Eliminating Peripheral Dipole
by Yao-Chih Lu, Yu-Tsz Hsu, Tsung-Yen Yang, I-Chun Liou, Sheng-Wei Wang, Po-Chia Huang, Jey-Jau Lee, Long-Li Lai and Hsiu-Fu Hsu
Nanomaterials 2022, 12(2), 185; https://doi.org/10.3390/nano12020185 - 6 Jan 2022
Cited by 1 | Viewed by 1475
Abstract
Three new amino-s-triazine-based dendrons, 1a, 1b, and 1c, containing an aryl-CN moiety in the dendritic skeleton were prepared in 72–81% yields (1a: R1 = − N(n-C8H17)2, R [...] Read more.
Three new amino-s-triazine-based dendrons, 1a, 1b, and 1c, containing an aryl-CN moiety in the dendritic skeleton were prepared in 72–81% yields (1a: R1 = − N(n-C8H17)2, R2 = n-OC8H17, 1b: R1 = R2 = − N(n-C8H17)2, 1c: R1 = − N(n-C8H17)2, R2 = − N(n-C4H9)2). Dendrons 1a with N(n-C8H17)2 and n-OC8H17 peripheral substituents, surprisingly, did not show any mesogenic phase during the thermal process. However, non-mesogenic 1a can be converted to mesogenic 1b or 1c by eliminating the peripheral dipole arising from the alkoxy substituent; dendron 1b only comprising the same N(n-C8H17)2 peripheral groups showed a ~25 °C mesogenic range on heating and ~108 °C mesogenic range on cooling. In contrast, dendron 1c possessing different N(n-CmH2m+1)2 (m = 8 versus m = 4) peripheral units, having similar stacking as 1b, exhibited a columnar phase on thermal treatment, but its mesogenic range (~9 and ~66 °C on heating and cooling, respectively) was much narrower than that of 1b, attributed to 1c’s less flexible alkyl chains in the peripheral part of dendron. Dendron 1a with the alkoxy substituent in the peripheral skeleton, creating additional dipole correspondingly, thus, leads to the dendritic molecules having a non-mesogenic stacking. Without the peripheral dipole for intermolecular side-by-side interaction, dendrons 1b and 1c exhibit a columnar phase on thermal treatment because of the vibration from the peripheral alkyl chain. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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20 pages, 3090 KiB  
Article
All Structures Great and Small: Nanoscale Modulations in Nematic Liquid Crystals
by Edward T. Samulski, Denisse Reyes-Arango, Alexandros G. Vanakaras and Demetri J. Photinos
Nanomaterials 2022, 12(1), 93; https://doi.org/10.3390/nano12010093 - 29 Dec 2021
Cited by 12 | Viewed by 2064
Abstract
The nature of the nanoscale structural organization in modulated nematic phases formed by molecules having a nonlinear molecular architecture is a central issue in contemporary liquid crystal research. Nevertheless, the elucidation of the molecular organization is incomplete and poorly understood. One attempt to [...] Read more.
The nature of the nanoscale structural organization in modulated nematic phases formed by molecules having a nonlinear molecular architecture is a central issue in contemporary liquid crystal research. Nevertheless, the elucidation of the molecular organization is incomplete and poorly understood. One attempt to explain nanoscale phenomena merely “shrinks down” established macroscopic continuum elasticity modeling. That explanation initially (and mistakenly) identified the low temperature nematic phase (NX), first observed in symmetric mesogenic dimers of the CB-n-CB series with an odd number of methylene spacers (n), as a twist–bend nematic (NTB). We show that the NX is unrelated to any of the elastic deformations (bend, splay, twist) stipulated by the continuum elasticity theory of nematics. Results from molecular theory and computer simulations are used to illuminate the local symmetry and physical origins of the nanoscale modulations in the NX phase, a spontaneously chiral and locally polar nematic. We emphasize and contrast the differences between the NX and theoretically conceivable nematics exhibiting spontaneous modulations of the elastic modes by presenting a coherent formulation of one-dimensionally modulated nematics based on the Frank–Oseen elasticity theory. The conditions for the appearance of nematic phases presenting true elastic modulations of the twist–bend, splay–bend, etc., combinations are discussed and shown to clearly exclude identifications with the nanoscale-modulated nematics observed experimentally, e.g., the NX phase. The latter modulation derives from packing constraints associated with nonlinear molecules—a chiral, locally-polar structural organization indicative of a new type of nematic phase. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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12 pages, 3807 KiB  
Article
Effect of Amorphous Crosslinker on Phase Behavior and Electro-Optic Response of Polymer-Stabilized Blue Phase Liquid Crystals
by Kyung Min Lee, Urice Tohgha, Timothy J. Bunning, Michael E. McConney and Nicholas P. Godman
Nanomaterials 2022, 12(1), 48; https://doi.org/10.3390/nano12010048 - 24 Dec 2021
Cited by 6 | Viewed by 2748
Abstract
Blue phase liquid crystals (BPLCs) composed of double-twisted cholesteric helices are promising materials for use in next-generation displays, optical components, and photonics applications. However, BPLCs are only observed in a narrow temperature range of 0.5–3 °C and must be stabilized with a polymer [...] Read more.
Blue phase liquid crystals (BPLCs) composed of double-twisted cholesteric helices are promising materials for use in next-generation displays, optical components, and photonics applications. However, BPLCs are only observed in a narrow temperature range of 0.5–3 °C and must be stabilized with a polymer network. Here, we report on controlling the phase behavior of BPLCs by varying the concentration of an amorphous crosslinker (pentaerythritol triacrylate (PETA)). LC mixtures without amorphous crosslinker display narrow phase transition temperatures from isotropic to the blue phase-II (BP-II), blue phase-I (BP-I), and cholesteric phases, but the addition of PETA stabilizes the BP-I phase. A PETA content above 3 wt% prevents the formation of the simple cubic BP-II phase and induces a direct transition from the isotropic to the BP-I phase. PETA widens the temperature window of BP-I from ~6.8 °C for BPLC without PETA to ~15 °C for BPLC with 4 wt% PETA. The BPLCs with 3 and 4 wt% PETA are stabilized using polymer networks via in situ photopolymerization. Polymer-stabilized BPLC with 3 wt% PETA showed switching between reflective to transparent states with response times of 400–500 μs when an AC field was applied, whereas the application of a DC field induced a large color change from green to red. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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Review

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15 pages, 2881 KiB  
Review
Unconventional Approaches to Prepare Triazine-Based Liquid Crystal Dendrimers
by Yao-Chih Lu, Hsiu-Fu Hsu and Long-Li Lai
Nanomaterials 2021, 11(8), 2112; https://doi.org/10.3390/nano11082112 - 19 Aug 2021
Cited by 7 | Viewed by 2313
Abstract
Most triazine-based liquid crystalline (LC) dendrimers reported thus far are the main-chain LC macromolecules with long flexible chains at their periphery and attached to internal rigid or semi-rigid frameworks. Their formation of mesogenic phases often depends on the intermolecular face-to-face π–π interactions between [...] Read more.
Most triazine-based liquid crystalline (LC) dendrimers reported thus far are the main-chain LC macromolecules with long flexible chains at their periphery and attached to internal rigid or semi-rigid frameworks. Their formation of mesogenic phases often depends on the intermolecular face-to-face π–π interactions between dendritic molecules, which are unusual. Their mesogenic phases can also be formed by incorporation of mesogenic units to the dendritic skeletons through long flexible chains, as most side-chain LC dendrimers, in which the peripheral mesogenic units generally play the important roles. For main-chain triazine-based dendrimers, their morphology is maintained by restricted freedom of rigid or semi-rigid connecting units, and their formations of LC phases are therefore not straightforward to be controlled. In this review, we thus describe modulating of the intermolecular face-to-face π–π interactions between the triazine-based dendritic molecules, with the aim of forming LC phases through molecular design. Full article
(This article belongs to the Special Issue Recent Advances in Nanostructured Liquid Crystals: From Supramolecular Order to Applications)
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