Showing papers on "Lyotropic liquid crystal published in 2020"

Advances in lyotropic liquid crystal systems for skin drug delivery.

Abstract: Lyotropic liquid crystals (LLCs) are organized mesophases with intermediate properties between liquids and solids. The LLC and its liquid crystalline nanoparticles (LCNPs) have attracted great inte...

Novel Trends in Lyotropic Liquid Crystals

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 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.

Tunable Diffraction Gratings from Biosourced Lyotropic Liquid Crystals

Abstract: Diffraction gratings are important for modern optical components, such as optical multiplexers and signal processors. Although liquid crystal (LC) gratings based on thermotropic LCs have been extensively explored, they often require expensive molecules and complicated manufacturing processes. Lyotropic LCs, which can be broadly obtained from both synthetic and natural sources, have not yet been applied in optical gratings. Herein, a facile grating fabrication method using a biosourced lyotropic LC formed by cellulose nanocrystals (CNCs), a material extracted from plants, is reported. Hydrogel sheets with vertically aligned uniform periodic structures are obtained by fixing the highly oriented chiral nematic LC of CNCs in polymer networks under the cooperative effects of gravity on phase separation and a magnetic field on LC orientation. The hydrogel generates up to sixth-order diffraction spots and shows linear polarization selectivity, with tunable grating periodicity controlled through LC concentration regulation. This synthesis strategy can be broadly applied to various grating materials and opens up a new area of optical materials from lyotropic LCs.

Design and Characterization of Glyceryl Monooleate-Nanostructures Containing Doxorubicin Hydrochloride.

Abstract: Glyceryl monooleate (GMO) is one of the most popular amphiphilic lipids, which, in the presence of different amounts of water and a proper amount of stabilizer, can promote the development of well defined, thermodynamically stable nanostructures, called lyotropic liquid crystal dispersions. The aim of this study is based on the design, characterization, and evaluation of the cytotoxicity of lyotropic liquid crystal nanostructures containing a model anticancer drug such as doxorubicin hydrochloride. The drug is efficiently retained by the GMO nanosystems by a remote loading approach. The nanostructures prepared with different non-ionic surfactants (poloxamers and polysorbates) are characterized by different physico-chemical features as a function of several parameters, i.e., serum stability, temperature, and different pH values, as well as the amount of cryoprotectants used to obtain suitable freeze-dried systems. The nanostructures prepared with poloxamer 407 used as a stabilizer show an increased toxicity of the entrapped drug on breast cancer cell lines (MCF-7 and MDA-MB-231) due to their ability to sensitize multidrug-resistant (MDR) tumor cells through the inhibition of specific drug efflux transporters. Moreover, the interaction between the nanostructures and the cells occurs after just a few hours, evidencing a huge cellular uptake of the nanosystems.

Tuning Water Networks via Ionic Liquid/Water Mixtures.

Abstract: Water in nanoconfinement is ubiquitous in biological systems and membrane materials, with altered properties that significantly influence the surrounding system. In this work, we show how ionic liquid (IL)/water mixtures can be tuned to create water environments that resemble nanoconfined systems. We utilize molecular dynamics simulations employing ab initio force fields to extensively characterize the water structure within five different IL/water mixtures: [BMIM + ][BF 4 - ], [BMIM + ][PF 6 - ], [BMIM + ][OTf - ], [BMIM + ][NO 3 - ]and [BMIM + ][TFSI - ] ILs at varying water fraction. We characterize water clustering, hydrogen bonding, water orientation, pairwise correlation functions and percolation networks as a function of water content and IL type. The nature of the water nanostructure is significantly tuned by changing the hydrophobicity of the IL and sensitively depends on water content. In hydrophobic ILs such as [BMIM + ][PF 6 - ], significant water clustering leads to dynamic formation of water pockets that can appear similar to those formed within reverse micelles. Furthermore, rotational relaxation times of water molecules in supersaturated hydrophobic IL/water mixtures indicate the close-connection with nanoconfined systems, as they are quantitatively similar to water relaxation in previously characterized lyotropic liquid crystals. We expect that this physical insight will lead to better design principles for incorporation of ILs into membrane materials to tune water nanostructure.

Chiral shape fluctuations and the origin of chirality in cholesteric phases of DNA origamis

Abstract: Lyotropic cholesteric liquid crystal phases are ubiquitously observed in biological and synthetic polymer solutions, characterized by a complex interplay between thermal fluctuations and entropic and enthalpic forces. The elucidation of the link between microscopic features and macroscopic chiral structure, and of the relative roles of these competing contributions on phase organization, remains a topical issue. Here, we provide theoretical evidence of a previously unidentified mechanism of chirality amplification in lyotropic liquid crystals, whereby phase chirality is governed by fluctuation-stabilized helical deformations in the conformations of their constituent molecules. Our results compare favorably to recent experimental studies of DNA origami assemblies and demonstrate the influence of intramolecular mechanics on chiral supramolecular order, with potential implications for a broad class of experimentally relevant colloidal systems.

Extremely small twist elastic constants in lyotropic nematic liquid crystals.

Abstract: Recent measurements of the elastic constants in lyotropic chromonic liquid crystals (LCLCs) have revealed an anomalously small twist elastic constant compared to the splay and bend constants. Interestingly, measurements of the elastic constants in the micellar lyotropic liquid crystals (LLCs) that are formed by surfactants, by far the most ubiquitous and studied class of LLCs, are extremely rare and report only the ratios of elastic constants and do not include the twist elastic constant. By means of light scattering, this study presents absolute values of the elastic constants and their corresponding viscosities for the nematic phase of a standard LLC composed of disk-shaped micelles. Very different elastic moduli are found. While the splay elastic constant is in the typical range of 1.5 pN as is true in general for thermotropic nematics, the twist elastic constant is found to be one order of magnitude smaller (0.30 pN) and almost two orders of magnitude smaller than the bend elastic constant (21 pN). These results demonstrate that a small twist elastic constant is not restricted to the special case of LCLCs, but is true for LLCs in general. The reason for this extremely small twist elastic constant very likely originates with the flexibility of the assemblies that are the building blocks of both micellar and chromonic lyotropic liquid crystals.

Surfactant-based lyotropic liquid crystal gels – the interplay between anisotropic order and gel formation

Abstract: Surfactant-based lyotropic liquid crystal gels (LLCGs) are soft materials which combine the anisotropic order of a surfactant-based lyotropic liquid crystal with the mechanical stability of a gel. The most prominent example of a “natural“ LLCG is the biological cell. This review summarizes potential applications of surfactant-based LLCGs and the different strategies via which these materials can be obtained. The main focus, however, is on gelation with low molecular weight gelators (LMWG), which form self-assembled fibrillar networks (SAFiN). We will discuss whether or not the resulting surfactant-based LLCGs are orthogonal self-assembled systems, i.e. systems where the two coexisting structures (lyotropic liquid crystal and SAFiN) form independently.

Size-Dependent Encapsulation and Release of dsDNA from Cationic Lyotropic Liquid Crystalline Cubic Phases.

Abstract: The potential of gene therapy has not yet been realized, largely due to difficulties in the targeted delivery of DNA to tissues and cells. Lipid-based nanovectors are of potential use in gene therapy due to their ability to enhance fusion with cellular membranes and transport the large polyanionic DNA molecules into the cytoplasm. While the research to date has mainly focused on liposome-based vectors, recently, nonlamellar phases with more complex internal architectures based on hexagonal or cubic symmetry have received increasing research attention due to their fusogenic properties, which may promote uptake of the DNA into the cell. Herein, we have carried out a fundamental physicochemical study to systematically analyze the encapsulation and release of nonfunctional double-stranded (ds) DNA fragments within monoolein (MO)-based cationic lipid phases of cubic symmetry (cationic cubic phases) and their dispersed submicron particles (cationic cubosomes). MO-based cationic cubic phases, both as the bulk phase and cubosomes, were formulated using six different cationic lipids, and their nanostructure was characterized in a high-throughput manner by synchrotron small-angle X-ray scattering (SAXS). dsDNA encapsulation was confirmed using agarose gel electrophoresis, and the effect on the internal nanostructure, size, and morphology of the cubosomes was investigated using synchrotron SAXS, dynamic light scattering, and cryo-transmission electron microscopy. Synchrotron radiation circular dichroism confirmed that the structure of the dsDNA fragments was unaffected by encapsulation within the cationic cubosome. The use of commercially available dsDNA ladders consisting of a controlled mixture of dsDNA fragments allowed us to determine release rates as a function of fragment size in a reasonably high throughput manner. An improved understanding of the loading capacity and release profile of nonfunctional biomolecules in cationic cubosomes will assist in the design of novel lipid nanovectors for gene delivery.

Lamellar Lyotropic Liquid Crystal Superior to Micellar Solution for Proton Conduction in an Aqueous Solution of 1-Tetradecyl-3-methylimidazolium Hydrogen Sulfate.

Abstract: Humidified perfluorosulfonic acid polymers with a nanoscopic phase-separated morphology are highly proton-conductive materials for fuel cells, yet morphology tuning of the acidic materials for enha...

Chaining of hard disks in nematic needles: particle-based simulation of colloidal interactions in liquid crystals.

Abstract: Colloidal particles suspended in liquid crystals can exhibit various effective anisotropic interactions that can be tuned and utilized in self-assembly processes. We simulate a two-dimensional system of hard disks suspended in a solution of dense hard needles as a model system for colloids suspended in a nematic lyotropic liquid crystal. The novel event-chain Monte Carlo technique enables us to directly measure colloidal interactions in a microscopic simulation with explicit liquid crystal particles in the dense nematic phase. We find a directional short-range attraction for disks along the director, which triggers chaining parallel to the director and seemingly contradicts the standard liquid crystal field theory result of a quadrupolar attraction with a preferred $${45^{\circ }}$$ angle. Our results can be explained by a short-range density-dependent depletion interaction, which has been neglected so far. Directionality and strength of the depletion interaction are caused by the weak planar anchoring of hard rods. The depletion attraction robustly dominates over the quadrupolar elastic attraction if disks come close. Self-assembly of many disks proceeds via intermediate chaining, which demonstrates that in lyotropic liquid crystal colloids depletion interactions play an important role in structure formation processes.

Formation of ion gels by polymerization of block copolymer/ionic liquid/oil mesophases.

Abstract: In this study, we introduce a new method of developing ion gels through polymerization of lyotropic liquid crystal (LLC) templates of monomer (styrene), cross-linker (divinylbenzene), ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate), and amphiphilic block copolymers (Pluronic F127). The polymerization of the oil phase boosts the mechanical properties of the ion-conducting electrolytes. We discuss the effect of tortuosity induced by crystalline domains and LLC structure on the conductivity of ion gels. The ion transport in polymerized LLCs (polyLLCs) can be controlled by changing the composition of the mesophases. Increasing the block copolymer concentration enhances the crystallinity of PEO blocks in the conductive domains, which slows down the dynamics of PEO chain and ion transport. We show that by adjusting the composition of LLC mesophases, the mechanical strength of ion gels can be increased one order of magnitude without compromising the ionic conductivity. The polyLLCs with 45/25/30 wt% (block copolymer/IL/oil) composition has storage modulus and ionic conductivity higher than 1 MPa and 3 mS cm-1 at 70 °C, respectively. The results suggest that LLC templating is a promising method to develop highly conductive ion gels, which provides advantages in terms of variety and processing.

Structural, thermal, dielectric and optical behaviour investigations of water-free ZnO/lyotropic liquid crystal nanocolloids

Abstract: Zinc oxide (ZnO) nanoparticles of spherical symmetry (average size of ≈ 20 nm) have been synthesised via a non-aqueous lyotropic liquid crystalline (LLC) templating process. Lyotropic liquid crysta...

Structural relationships for the design of responsive azobenzene-based lyotropic liquid crystals.

Abstract: Light-responsive binary (azobenzene + solvent) lyotropic liquid crystals (LCs) were investigated by structural modification of simple azobenzene molecules. Three benzoic acid-containing azobenzene molecules 4-(4-(hydroxyphenyl)diazenyl)benzoic acid (AZO1), 3-(4-(hydroxyphenyl)diazenyl)benzoic acid (AZO2) and 5-(4-(hydroxyphenyl)diazenyl)isophthalic acid (AZO3) were produced with various amide substitutions to produce tectons with a variety of hydrophobicity, size and branching. The LC mesophases formed by binary (azobenzene + solvent) systems with low volatility solvents dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF) as well as the protic ionic liquids ethylammonium formate (EAF) and propylammonium formate (PAF), were investigated using a combination of small-angle X-ray and neutron scattering (SAXS and SANS) as well as polarising light microscopy (PLM). Increasing alkyl group length was found to have a strong influence on LC phase spacing, and changes in the position of substitution on the benzene ring influenced the preferred curvature of phases. UV-induced trans to cis isomerization of the samples was shown to influence ordering and optical birefringence, indicating potential applications in optical devices.

Lyotropic Liquid Crystal-Based Membranes for Water Remediation: Fabrication, Characterization and Performance Evaluation.

Abstract: In water remediation, biomimetic membranes are gaining much attention due to their selectivity, dynamic stability, nontoxicity, and biocompatibility. Lyotropic liquid crystals (LLCs) are self-organ...

Role of Defects in Achieving Highly Asymmetric Lamellar Self-Assembly in Block Copolymer/Homopolymer Blends.

Abstract: Lamellar structure is a prominent state in soft condensed matter. Swelling lamellar layers to highly asymmetric structures by a second component is a facile, cost-effective strategy to impart materials with adaptive size and tunable properties. One key question that remains unsolved is how defects form and affect the asymmetric lamellar order. This study unravels the role of defects by swelling a miktoarm block copolymer with a homopolymer. Ordered lamellae first lose translational order by a significant increase in the number of dislocations and then lose orientational order by the generation of disclinations. The homopolymers are not uniformly distributed in defective lamellae and primarily segregate in the vicinity of disclination cores. The free energy of defects is mainly contributed by molecular splay and significantly alleviated by an increased radius of local curvature. This study provides direct evidence to reveal the role of defects and lamellar order in block copolymer/homopolymer blends and also sheds light on understanding analogous structural transitions in other soft systems, including lyotropic liquid crystals, phospholipid membranes, and polymer nanocomposites.

Mesomorphic Ceramic Films Synthesized via Lyotropic Self-Assembly of Metal Oxide Nanorods Complete with Sintering

Abstract: Mesomorphic ceramics are broadly defined as solid systems with morphologies intermediate between isotropic materials and single crystals. To illustrate this materials concept, a class of mesomorphi...

A Lyotropic Liquid Crystal from a Flexible Oligopeptide Amphiphile in Dimethyl Sulfoxide

Abstract: Despite the rapid progress in peptide liquid crystals (LCs) due to their prominent properties, our investigation on flexible peptide-based LCs is incomplete, mainly resulted from their unclear form...

Peculiar hydrogen bonding behaviour of water molecules inside the aqueous nanochannels of lyotropic liquid crystals

Abstract: In spite of the widespread utilizations of lyotropic liquid crystals (LLCs) in food technology, as nanoreactors and in biomedical fields, the exact nature of their aqueous nanochannels which are deemed to dictate these applications are not completely understood. In this context, elucidation of the hydrogen bonding properties of the water molecules inside the nanochannels will contribute towards obtaining a complete picture of the LLC materials. In this study, we use two molecules exhibiting an excited state intramolecular proton transfer (ESIPT), fisetin and 3-hydroxyflavone, to determine the hydrogen bond donating and accepting parameters of the LLC water molecules. The steady state results imply a heterogeneity in the hydrogen bond accepting and donating properties inside the LLC nanochannels. Upon photoexcitation of the normal form of the ESIPT molecules, we notice that despite a reported general alcohol like polarity of the LLC nanochannels, the hydrogen bonding behaviour of the water molecules is similar to that of moderately polar aprotic solvents such as acetonitrile. In contrast, on excitation of the anionic species we observe that the spectral pattern is similar to that in alcohols. Additionally, the effect of the LLC water molecules on the rate of the intramolecular hydrogen transfer process has been explored. The ESIPT rates of both the probes, which are ultrafast (<20 ps) in neat polar protic and aprotic solvents, get slowed down dramatically by almost 15 times inside the LLC phases. Such an extent of retardation in the ESIPT rate is extremely rare in the literature, which signals towards the unique behaviour of the water molecules inside the LLC nanochannels. The structural topology of the LLC phases also influences the ESIPT rate with the timescale of the process increasing from the cubic to the hexagonal phase.

A nanostructured bifunctional acid–base catalyst resin formed by lyotropic liquid crystal monomers

Abstract: An ordered, nanoporous polymer resin was prepared from the self-assembly of lyotropic liquid crystal monomers and employed as a heterogeneous, bifunctional catalyst. This material contains antagoni...

3D Volumetric Structural Hierarchy Induced by Colloidal Polymerization of a Quantum-Dot Ionic Liquid Monomer Conjugate

Abstract: Hierarchically structured emissive quantum dot (CdS/CdSe) poly(ionic liquid) composites are synthesized through colloidal polymerization within a lyotropic liquid crystal, yielding a solvent-respon...

Modification of Mesoporous LiMn2O4 and LiMn2−xCoxO4 by SILAR Method for Highly Efficient Water Oxidation Electrocatalysis

Abstract: DOI: 10.1002/admt.202000353 in recent years.[6–11] However, cobalt is a toxic, and relatively low abundant element that needs to be changed with a more abundant and less toxic element, such as manganese. Manganese oxides and mixed oxides have also been investigated that displayed a lower OER efficiency and lower stability.[12–17] Most studies show that the cobalt is a key element for an efficient OER such that incorporation of cobalt into manganese oxide lattice improves the OER efficiency and stability of a modified electrode.[17] Mesoporous metal oxides have been targeted as efficient electrocatalysts for the OER. Several synthetic protocols, including hard and soft templating methods have been developed to produce mesoporous metal oxides.[21–27] Hard templating method typically uses ordered mesoporous silica or carbon as a mold to produce ordered mesoporous metal oxide powders.[24,25]Soft templating methods, such as evaporation induced self-assembly[23] and molten salt assisted selfassembly (MASA)[24–27]processes, have been developed for the fabrication of mesoporous metal oxide thin films that would be more practical in an electrochemical process. The MASA process is a more applicable method to produce disordered mesoporous transition metal oxides of metals that do not have alkoxide precursors; the metal precursors used in this process are usually metal nitrate, metal acetate, or metal chloride salts.[24–27] In the MASA process, a transition metal salt that has low melting point (such as first raw transition metal nitrates) or high solubility (such as most lithium salts) could be used as a solvent to assemble surfactant molecules into a lyotropic liquid crystalline mesophase.[28–31] Salt is in a molten phase in the mesophase (confined nanospace in hydrophilic domains) due to nanospace effect (NE).[30] The NE, not only reduces the melting point of the salts,[30] also enhances the solubility of the salts.[31] Moreover, presence of two salts (lithium and transition metal salts) creates a synergistic effect that further improves the stability and high salt uptake of the salt-surfactant mesophases. Coating of a mesophase as a thin film and its calcination at elevated temperatures produce mesoporous metal oxide thin films.[26–38] The MASA process has already been employed to two groups of metal oxides. In the first group, a silica or titania precursor is used as a polymerizing agent at room temperature together with a transition metal nitrate salt to produce Iridium, ruthenium, and cobalt oxides are target materials as efficient and stable mesoporous metal oxide electrocatalysts for oxygen evolution reaction (OER). However, they are costly, toxic, and not practical for an efficient OER process. Here, a two-step method is introduced, based on earthabundant manganese; molten salt-assisted self-assembly process to prepare mesoporous LiMn2−xCoxO4 (x = 0–0.5) modified electrodes, in which a systematic incorporation of Co(II) into the structure is performed using successive ionic layer adsorption and reaction followed by an annealing (SILAR-AN) process. Applying SILAR-AN over a stable m-LiMn1.6Co0.4O4 electrode improves the OER performance; the Tafel slope and overpotential drop from 66 to 46 mV dec−1 and 304 to 265 mV (at 1.0 mA cm−2), respectively. The performance of the modified electrodes is comparable to benchmark IrO2 and RuO2 catalysts and much better than cobalt oxide electrodes. Electronic interactions between the neighboring Mn and Co sites synergistically amplify the OER performance of the m-LiMn2−xCoxO4 electrodes. The data are compatible with an eight steps nucleophilic acid-base reaction mechanism during OER.

Evolution of structural dimensions in mesoporous template precursor from hexagonal lyotropic liquid crystals

Abstract: Producing nanopores from hexagonal lyotropic liquid crystals (LLCs) templates requires not only retaining phase morphology of the templates but also precisely controlling structural dimensions of unit cells. In this study, SAXS and 2H NMR are used to investigate dimensional evolutions of ternary systems consisting of polymerizable species, (ethylene glycol) diacrylate (PEGDA) and/or 2-hydroxyethyl methacrylate (HEMA), in a LLCs template of hexagonally packed cylinders formed from dodecyl trimethylammonium bromide (DTAB) and water. With the addition of those polymerizable species, the system rearranges into a new hexagonal system with a smaller aggregation number, smaller pores and a thicker pore wall thickness. The hexagonal system will coexist with an aqueous-rich phase containing isotropically distributed DTAB if sufficient PEGDA is applied but the single hexagonal system could be restored by partially replacing the PEGDA with HEMA. The mobility of DTAB molecules within the aggregates varies depending on monomer compositions. The changes in structural dimensions of the unit cells and phase behaviors after adding polymerizable monomers allow dimensional control of mesochannels and potentially enable the control of selectivity and robustness of polymerized nanomaterials via molecular design.

Lyotropic liquid crystal to measure residual dipolar couplings in dimethyl sulfoxide based on modified cellulose nanocrystals

Abstract: A novel lyotropic liquid crystal (LCC) was developed by grafting polymer brushes onto cellulose nanocrystals (CNCs) via free radical polymerization. It shows alignment properties to measure residual dipolar couplings (RDCs) of small organic molecules in DMSO without interference from background NMR signals of the polymer.

The Effects of Size and Shape Dispersity on the Phase Behavior of Nanomesogen Lyotropic Liquid Crystals

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, 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.