Special Issue "New Trends in Lyotropic Liquid Crystals"

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

Deadline for manuscript submissions: closed (30 June 2020).

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Antonio Martins Figueiredo Neto
E-Mail Website
Guest Editor
Institute of Physics, University of São Paulo, Rua do Matão Nr.1371 CEP 05508-090 Cidade Universitária, São Paulo, Brazil
Interests: magnetic colloids; lyotropic liquid crystals; low-density lipoproteins; nonlinear optical properties; structure of mesophases
Dr. Ingo Dierking
E-Mail Website
Guest Editor
Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
Interests: liquid crystals; chiral liquid crystals; ferroelectric liquid crystals; polymer stabilized liquid crystals; nanoparticles in anisotropic fluids; liquid crystal-nanotube dispersions; defects and defect dynamics; phase ordering in soft matter; fractal structures
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Special Issue Information

Dear colleagues,

The liquid crystalline state of matter has been investigated for more than 100 years by many researchers from different branches of science, technology, and even the arts. Materials presenting liquid crystal properties are present in our daily lives (e.g., cell phones, watches, thermometers, and displays). The great majority of these materials belong to the family of thermotropic liquid crystals. Liquid crystalline properties are also present in mixtures of amphiphilic molecules and solvents, or shape-anisotropic colloids in solvents, which constitute the family of lyotropic liquid crystals. These have attracted a great deal of interest in recent years, despite the fact that technological applications of these materials are not widespread. Some outstanding aspects make lyotropics very attractive for research: The richness of their phase diagrams, showing structures not present in thermotropics; Their closeness with biological systems (e.g., the cell membrane structure); The kosmotropic and chaotropic (bonding/order inducing and disrupting) characteristic of the chemical groups present in some molecules forming lyotropics give interesting information about the water arrangement (solvation water) at the solute/solvent interface; and the possibility of exploiting their self-organization in nanotechnology, as templates. Recently, new mixtures have been proposed, enlarging the possibility of new structures and exciting new properties. It is expected that in the near future, research in lyotropics will increasingly impact biology and medicine—in particular in the field of drug delivery with low toxicity, membrane permeation, and elasticity.

We invite colleagues to submit papers exploring the different aspects of the physico-chemical properties of lyotropic liquid crystals.

The potential topics include, but are not limited to:

  • New lyotropic mixtures
  • Property characterization (structure, linear and nonlinear optics, etc.)
  • Chromonic lyotropic liquid crystals
  • Chemical stability of lyotropic mixtures
  • Inorganic and colloidal lyotropic liquid crystals
  • Defects in lyotropic mesophases
  • Elasticity in lyotropic structures
  • Biaxial and uniaxial nematic phases
  • Applications of lyotropics
  • Interface with biological and biomedical research
  • Lyotropic inorganic liquid crystals
  • Lyotropic phases from colloidal nanoparticles

Prof. Dr. Antonio Martins Figueiredo Neto
Dr. Ingo Dierking
Guest Editors

Manuscript Submission Information

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Keywords

  • structure, polymorphism, physico-chemical properties
  • interface biology, drug delivery
  • chromonics
  • shape-anisotropic colloids, nanorods, 2D materials
  • cellulose nano-crystals
  • elasticity, defects
  • flexoelectricity, ferroelectricity
  • applications

Published Papers (10 papers)

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Research

Jump to: Review

Open AccessArticle
Magnetic Field and Dilution Effects on the Phase Diagrams of Simple Statistical Models for Nematic Biaxial Systems
Crystals 2020, 10(8), 632; https://doi.org/10.3390/cryst10080632 - 22 Jul 2020
Viewed by 560
Abstract
We use a simple statistical model to investigate the effects of an applied magnetic field and of the dilution of site elements on the phase diagrams of biaxial nematic systems, with an emphasis on the stability of the Landau multicritical point. The statistical [...] Read more.
We use a simple statistical model to investigate the effects of an applied magnetic field and of the dilution of site elements on the phase diagrams of biaxial nematic systems, with an emphasis on the stability of the Landau multicritical point. The statistical lattice model consists of intrinsically biaxial nematogenic units, which interact via a Maier–Saupe potential, and which are characterized by a discrete choice of orientations of the microscopic nematic directors. According to previous calculations at zero field and in the absence of dilution, we regain the well-known sequence of biaxial, uniaxial, and disordered structures as the temperature is increased, and locate the Landau point. We then focus on the topological changes induced in the phase diagram by the application of an external magnetic field, and show that the Landau point is destabilized by the presence of an applied field. On the other hand, in the absence of a field, we show that only a quite strong dilution of nematic sites is capable of destabilizing the Landau point. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessArticle
Flexible and Structural Coloured Composite Films from Cellulose Nanocrystals/Hydroxypropyl Cellulose Lyotropic Suspensions
Crystals 2020, 10(2), 122; https://doi.org/10.3390/cryst10020122 - 16 Feb 2020
Cited by 2 | Viewed by 1365
Abstract
Lyotropic colloidal aqueous suspensions of cellulose nanocrystals (CNCs) can, after solvent evaporation, retain their chiral nematic arrangement. As water is removed the pitch value of the suspension decreases and structural colour-generating films, which are mechanically brittle in nature, can be obtained. Increasing their [...] Read more.
Lyotropic colloidal aqueous suspensions of cellulose nanocrystals (CNCs) can, after solvent evaporation, retain their chiral nematic arrangement. As water is removed the pitch value of the suspension decreases and structural colour-generating films, which are mechanically brittle in nature, can be obtained. Increasing their flexibility while keeping the chiral nematic structure and biocompatible nature is a challenging task. However, if achievable, this will promote their use in new and interesting applications. In this study, we report on the addition of different amounts of hydroxypropyl cellulose (HPC) to CNCs suspension within the coexistence of the isotropic-anisotropic phases and infer the influence of this cellulosic derivative on the properties of the obtained solid films. It was possible to add 50 wt.% of HPC to a CNCs aqueous suspension (to obtain a 50/50 solids ratio) without disrupting the LC phase of CNCs and maintaining a left-handed helical structure in the obtained films. When 30 wt.% of HPC was added to the suspension of CNCs, a strong colouration in the film was still observed. This colour shifts to the near-infrared region as the HPC content in the colloidal suspension increases to 40 wt.% or 50 wt.% The all-cellulosic composite films present an increase in the maximum strain as the concentration of HPC increases, as shown by the bending experiments and an improvement in their thermal properties. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessArticle
Ordering of Rods near Surfaces: Concentration Effects
Crystals 2019, 9(5), 265; https://doi.org/10.3390/cryst9050265 - 21 May 2019
Viewed by 915
Abstract
We study the orientation of rods in the neighborhood of a surface. A semi-infinite region in two different situations is considered: (i) the rods are located close to a flat wall and (ii) the rods occupy the space that surrounds a sphere. In [...] Read more.
We study the orientation of rods in the neighborhood of a surface. A semi-infinite region in two different situations is considered: (i) the rods are located close to a flat wall and (ii) the rods occupy the space that surrounds a sphere. In a recent paper we investigated a similar problem: the interior of a sphere, with a fixed concentration of rods. Here, we allow for varying concentration, the rods are driven from a reservoir to the neighborhood of the surface by means of a tunable chemical potential. In the planar case, the particle dimensions are irrelevant. In the curved case, we consider cylinders with dimensions comparable to the radius of curvature of the sphere; as they come close to the surface, they have to accommodate to fill the available space, leading to a rich orientational profile. These systems are studied by a mapping onto a three-state Potts model with annealed disorder on a semi-infinite lattice; two order parameters describe the system: the occupancy and the orientation. The Hamiltonian is solved using a mean-field approach producing recurrence relations that are iterated numerically and we obtain various interesting results: the system undergoes a first order transition just as in the bulk case; the profiles do not have a smooth decay but may present a step and we search for the factors that determine their shape. The prediction of such steps may be relevant in the field of self-assembly of colloids and nanotechnology. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessArticle
Effect of Crowding Agent Polyethylene Glycol on Lyotropic Chromonic Liquid Crystal Phases of Disodium Cromoglycate
Crystals 2019, 9(3), 160; https://doi.org/10.3390/cryst9030160 - 19 Mar 2019
Cited by 2 | Viewed by 1628
Abstract
Adding crowding agents such as polyethylene glycol (PEG) to lyotropic chromonic liquid crystals (LCLCs) formed by water dispersions of materials such as disodium cromoglicate (DSCG) leads to a phase separation of the isotropic phase and the ordered phase. This behavior resembles nanoscale condensation [...] Read more.
Adding crowding agents such as polyethylene glycol (PEG) to lyotropic chromonic liquid crystals (LCLCs) formed by water dispersions of materials such as disodium cromoglicate (DSCG) leads to a phase separation of the isotropic phase and the ordered phase. This behavior resembles nanoscale condensation of DNAs but occurs at the microscale. The structure of condensed chromonic regions in crowded dispersions is not yet fully understood, in particular, it is not clear whether the condensed domains are in the nematic (N) or the columnar (C) state. In this study, we report on small angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements of mixtures of aqueous solutions of DSCG with PEG and compare results to measurements of aqueous solutions of pure DSCG. X-ray measurements demonstrate that addition of PEG to DSCG in the N phase triggers appearance of the C phase that coexists with the isotropic (I) phase. Within the coexisting region, the lateral distance between the columns of the chromonic aggregates decreases as the temperature is increased. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Review

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Open AccessReview
The Effects of Size and Shape Dispersity on the Phase Behavior of Nanomesogen Lyotropic Liquid Crystals
Crystals 2020, 10(8), 715; https://doi.org/10.3390/cryst10080715 - 18 Aug 2020
Viewed by 1038
Abstract
Self-assembly of anisotropic nanomaterials into fluids is a key step in producing bulk, solid materials with controlled architecture and properties. In particular, the ordering of anisotropic nanomaterials in lyotropic liquid crystalline phases facilitates the production of films, fibers, and devices with anisotropic mechanical, [...] Read more.
Self-assembly of anisotropic nanomaterials into fluids is a key step in producing bulk, solid materials with controlled architecture and properties. In particular, the ordering of anisotropic nanomaterials in lyotropic liquid crystalline phases facilitates the production of films, fibers, and devices with anisotropic mechanical, thermal, electrical, and photonic properties. While often considered a new area of research, experimental and theoretical studies of nanoscale mesogens date back to the 1920s. Through modern computational, synthesis, and characterization tools, there are new opportunities to design liquid crystalline phases to achieve complex architectures and enable new applications in opto-electronics, multifunctional textiles, and conductive films. This review article provides a brief review of the liquid crystal phase behavior of one dimensional nanocylinders and two dimensional nanoplatelets, a discussion of investigations on the effects of size and shape dispersity on phase behavior, and outlook for exploiting size and shape dispersity in designing materials with controlled architectures. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessReview
Novel Trends in Lyotropic Liquid Crystals
Crystals 2020, 10(7), 604; https://doi.org/10.3390/cryst10070604 - 12 Jul 2020
Cited by 4 | Viewed by 1177
Abstract
We introduce and shortly summarize a variety of more recent aspects of lyotropic liquid crystals (LLCs), which have drawn the attention of the liquid crystal and soft matter community and have recently led to an increasing number of groups studying this fascinating class [...] Read more.
We introduce and shortly summarize a variety of more recent aspects of lyotropic liquid crystals (LLCs), which have drawn the attention of the liquid crystal and soft matter community and have recently led to an increasing number of groups studying this fascinating class of materials, alongside their normal activities in thermotopic LCs. The diversity of topics ranges from amphiphilic to inorganic liquid crystals, clays and biological liquid crystals, such as viruses, cellulose or DNA, to strongly anisotropic materials such as nanotubes, nanowires or graphene oxide dispersed in isotropic solvents. We conclude our admittedly somewhat subjective overview with materials exhibiting some fascinating properties, such as chromonics, ferroelectric lyotropics and active liquid crystals and living lyotropics, before we point out some possible and emerging applications of a class of materials that has long been standing in the shadow of the well-known applications of thermotropic liquid crystals, namely displays and electro-optic devices. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessReview
From Equilibrium Liquid Crystal Formation and Kinetic Arrest to Photonic Bandgap Films Using Suspensions of Cellulose Nanocrystals
Crystals 2020, 10(3), 199; https://doi.org/10.3390/cryst10030199 - 13 Mar 2020
Cited by 19 | Viewed by 2706
Abstract
The lyotropic cholesteric liquid crystal phase developed by suspensions of cellulose nanocrystals (CNCs) has come increasingly into focus from numerous directions over the last few years. In part, this is because CNC suspensions are sustainably produced aqueous suspensions of a fully bio-derived nanomaterial [...] Read more.
The lyotropic cholesteric liquid crystal phase developed by suspensions of cellulose nanocrystals (CNCs) has come increasingly into focus from numerous directions over the last few years. In part, this is because CNC suspensions are sustainably produced aqueous suspensions of a fully bio-derived nanomaterial with attractive properties. Equally important is the interesting and useful behavior exhibited by solid CNC films, created by drying a cholesteric-forming suspension. However, the pathway along which these films are realized, starting from a CNC suspension that may have low enough concentration to be fully isotropic, is more complex than often appreciated, leading to reproducibility problems and confusion. Addressing a broad audience of physicists, chemists, materials scientists and engineers, this Review focuses primarily on the physics and physical chemistry of CNC suspensions and the process of drying them. The ambition is to explain rather than to repeat, hence we spend more time than usual on the meanings and relevance of the key colloid and liquid crystal science concepts that must be mastered in order to understand the behavior of CNC suspensions, and we present some interesting analyses, arguments and data for the first time. We go through the development of cholesteric nuclei (tactoids) from the isotropic phase and their potential impact on the final dry films; the spontaneous CNC fractionation that takes place in the phase coexistence window; the kinetic arrest that sets in when the CNC mass fraction reaches ∼10 wt.%, preserving the cholesteric helical order until the film has dried; the ’coffee-ring effect’ active prior to kinetic arrest, often ruining the uniformity in the produced films; and the compression of the helix during the final water evaporation, giving rise to visible structural color in the films. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessReview
The Lyotropic Analog of the Polar SmC* Phase
Crystals 2019, 9(11), 568; https://doi.org/10.3390/cryst9110568 - 29 Oct 2019
Cited by 3 | Viewed by 815
Abstract
Only six years ago, the first clear-cut example of a ferroelectric, lyotropic liquid crystal was discovered. Since then, ongoing investigations in this new research field provided numerous instances of the missing pieces to complete the formerly blank picture of the lyotropic smectic C* [...] Read more.
Only six years ago, the first clear-cut example of a ferroelectric, lyotropic liquid crystal was discovered. Since then, ongoing investigations in this new research field provided numerous instances of the missing pieces to complete the formerly blank picture of the lyotropic smectic C* (SmC*) phase. In this review we wanted to combine these new results and put them into a wider historical and scientific context. We start by giving an introduction about characteristic features of the well-known thermotropic SmC* phase and why it is so difficult to find a lyotropic equivalent of this fascinating phase. After discussing early examples of achiral lyotropic and swollen SmC phases, we recap the discovery of the first lyotropic SmC* phase. The molecular features necessary for its formation and its properties are analyzed. We place special emphasis on discussing the long-range orientational order of the tilt direction and the corresponding chirality effects. By comparing these exceptional features with thermotropic and swollen SmC* phases, we aim to improve not only the understanding of the lyotropic SmC* phase, but also of the relationship between thermotropic and lyotropic systems in general. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessReview
Lyotropic Liquid Crystals from Colloidal Suspensions of Graphene Oxide
Crystals 2019, 9(9), 455; https://doi.org/10.3390/cryst9090455 - 31 Aug 2019
Cited by 5 | Viewed by 1479
Abstract
Lyotropic liquid crystals from colloidal particles have been known for more than a century, but have attracted a revived interest over the last few years. This is due to the developments in nanoscience and nanotechnology, where the liquid crystal order can be exploited [...] Read more.
Lyotropic liquid crystals from colloidal particles have been known for more than a century, but have attracted a revived interest over the last few years. This is due to the developments in nanoscience and nanotechnology, where the liquid crystal order can be exploited to orient and reorient the anisotropic colloids, thus enabling, increasing and switching the preferential properties of the nanoparticles. In particular, carbon-based colloids like carbon nanotubes and graphene/graphene–oxide have increasingly been studied with respect to their lyotropic liquid crystalline properties over the recent years. We critically review aspects of lyotropic graphene oxide liquid crystal with respect to properties and behavior which seem to be generally established, but also discuss those effects that are largely unfamiliar so far, or as of yet of controversial experimental or theoretical outcome. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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Open AccessReview
Experimental Conditions for the Stabilization of the Lyotropic Biaxial Nematic Mesophase
Crystals 2019, 9(3), 158; https://doi.org/10.3390/cryst9030158 - 19 Mar 2019
Cited by 2 | Viewed by 1255
Abstract
Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the [...] Read more.
Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the discovery of the third one, named biaxial nematic phase (NB) in 1980, however, some controversies in the stability of biaxial nematic phases began and still continue in the literature. From the theoretical point of view, the existence of a biaxial nematic phase is well established. This review aims to bring information about the historical development of those phases considering the early studies and then summarize the recent studies on how to stabilize different nematic phases from the experimental conditions, especially, choosing the suitable constituents of lyotropic mixtures. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
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