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In lyotropic chromonic liquid crystals (LCLCs), twist distortion of the nematic director costs much less energy than splay or bend distortion. This feature leads to novel mirror-symmetry breaking director configurations when the LCLCs are confined by interfaces or contain suspended particles. Spherical colloids in an aligned LCLC nematic phase, for example, induce chiral director perturbations (“twisted tails”). The asymmetry of rod-like particles in an aligned LCLC offer a richer set of possibilities due to their aspect ratio (α) and mean orientation angle (〈θ〉) between their long axis and the uniform far-field director. Here we report on the director configuration, equilibrium orientation, and angular diffusion of rod-like particles with planar anchoring suspended in an aligned LCLC. Video microscopy reveals, counterintuitively, that two-thirds of the rods have an angled equilibrium orientation (〈θ〉 ≠ 0) that decreases with increasing α, while only one-third of the rods are aligned (〈θ〉 = 0). Polarized optical video-microscopy and Landau–de Gennes numerical modeling demonstrate that the angled and aligned rods are accompanied by distinct chiral director configurations. Angled rods have a longitudinal mirror plane (LMP) parallel to their long axis and approximately parallel to the substrate walls. Aligned rods have a transverse and longitudinal mirror plane (TLMP), where the transverse mirror plane is perpendicular to the rod's long axis. Effectively, the small twist elastic constant of LCLCs promotes chiral director configurations that modify the natural tendency of rods to orient along the far-field director. Additional diffusion experiments confirm that rods are angularly confined with strength that depends on α.

Understanding how soft matter deforms in response to mechanical interactions is central to the design of functional synthetic materials as well as elucidation of the behaviors of biological assemblies. Here we explore how cycles of thermally induced transitions between nematic (N) and isotropic (I) phases can be used to exert cyclical elastic stresses on dispersions of giant unilamellar vesicles (GUVs) and thereby evolve GUV shape and properties. The measurements were enabled by the finding that I–N–I phase transitions of the lyotropic chromonic liquid crystal disodium cromoglycate, when conducted via an intermediate columnar (M) phase, minimized transport of GUVs on phase fronts to confining surfaces. Whereas I to N phase transitions strained spherical GUVs into spindle-like shapes, with an efflux of GUV internal volume, subsequent N to I transitions generated a range of complex GUV shapes, including stomatocyte, pear- and dumbbell-like shapes that depended on the extent of strain in the N phase. The highest strained GUVs were observed to form buds (daughter vesicles) that we show, via a cycle of I–N–I–N phase transitions, are connected via a neck to the parent vesicle. Additional experiments established that changes in elasticity of the phase surrounding the GUVs and not thermal expansion of membranes were responsible for the shape transitions, and that I–N–I transformations that generate stomatocytes can be understood from the Bilayer-Coupling model of GUV shapes. Overall, these observations advance our understanding of how LC elastic stresses can be regulated to evolve the shapes of soft biological assemblies as well as provide new approaches for engineering synthetic soft matter.

This article demonstrates a new approach enabling the active control of swimming trajectories of flagellated bacteria in space and time. Bacteria were mixed with water solutions of disodium cromogl...

Spatial confinement of water-based lyotropic chromonic liquid crystals made of achiral molecules produces chiral structures with alternating left and right twists.

We study the effect of purification and impurities on the self-assembly and phase behavior of lyotropic chromonic liquid crystals (LCLCs). LCLC molecules in water stack to form aggregates; then, the elongated nanoaggregates align to make liquid crystalline phases. Utilizing multiple experimental techniques, we unveil impurities in commercial Sunset Yellow FCF (SSY), a representative LCLC, and how the precipitation-based purification promotes the formation of the aggregates and mesophase. We further explore the roles of intrinsic impurities, i.e., byproducts of the SSY synthesis, whose molecular structures are almost identical to that of SSY but differ only in the number and position of sulfonate groups. Combining quantum chemical calculations of molecular structures and experimental investigation of aggregate structures and phase behavior, we propose that the impurities of the planar shapes behave as planar SSY, i.e., participating in aggregate formation, whereas the nonplanar one disrupts the nematic phase. These results highlight the critical roles of the impurities and deepen our understanding of self-assembled aggregates and their aligned mesophases.

Achiral building blocks forming achiral structures is a common occurrence in nature, while chirality emerging spontaneously from an achiral system is usually associated with important scientific phenomena. We report on the spontaneous chiral symmetry-breaking phenomena upon the topographic confinement of achiral lyotropic chromonic liquid crystals in periodically arranged micrometer scale air pillars. The anisotropic fluid arranges into chiral domains that depend on the arrangement and spacing of the pillars. We characterize the resulting domains by polarized optical microscopy, support their reconstruction by numerical calculations, and extend the findings with experiments, which include chiral dopants. Well-controlled and addressed chiral structures will be useful in potential applications like programmable scaffolds for living liquid crystals and as sensors for detecting chirality at the molecular level., Well-addressed chiral domains are generated with achiral lyotropic chromonic liquid crystal materials using periodic air pillars, which can be potentially used for scaffolds for living matters.

Lyotropic chromonic liquid crystals (LCLCs) confined in cylindrical cavity can form an escaped-twisted (ET) configuration, resulting from the saddle-splay elastic constant is great much than twist ...

In a cylindrical cavity with a degenerate planar anchoring, the lyotropic chromonic nematic liquid crystals without intrinsic chirality tend to exhibit an escaped twisted configuration for the larg...

Coating-type polarizing films with a high dichroic ratio (DR) and polarization efficiency in the visible region were fabricated using a solution of ternary lyotropic chromonic liquid crystals (LCLCs). Optical characteristics of these anisotropic LCLC polarizing films were then determined. DR increased with increasing LCLC concentrations. Molecular ordering of these LCLCs on a rubbed polyimide (PI) layer increased because LCLC molecules' orientation was enhanced by the dielectric anisotropy effect from rubbing the surface of the PI. In addition, this study demonstrated how the interaction between liquid crystal aggregates and the PI surface with different LCLC solutions correlated with LCLC molecular orientations on the PI which is significantly dependent on whether the coating direction of the LCLC solution was parallel or perpendicular to the PI rubbing direction. It was found that the ordering direction at high LCLC concentrations was determined by shearing direction of the LCLC solution coating, whereas the ordering direction at low LCLC concentrations was governed by the dielectric anisotropy effect from the PI rubbing direction.

Positional order in the lyotropic chromonic liquid crystals (LCLCs) is investigated in the supramolecular assembly of benzene 1,3,5-tricarboxamide (BTA) derivatives with the glucono-delta-lactone (GdL) acid additive by high-resolution synchrotron radiation small-angle X-ray scattering. The formation of positionally ordered hexagonal phase is found to profoundly depend on the concentrations of BTA derivatives, cBTA, and GdL additives, caddtive, giving rise to unusual behavior distinctive from conventional lyotropic liquid crystals (LCs) with covalent bonds and fixed length. The hexagonal phase is observed to coexist with another phase in certain range of caddtive/cBTA. Intriguingly, the lattice spacing R of the hexagonal phase remains almost constant by varying caddtive but changes with cBTA. The above observations are attributed to unique sensitivities of the LCLC properties, such as the contour length and flexibility of individual cylinder assemblies and phase coexistence, to additives in the solutions. Our study reveals the complexity in positional ordering in the LCLCs which not only relates to the underlying principles of hierarchical reversible self-assembly but also attracts fundamental interests in LCs.

Ionic self-assembly is a simple yet powerful method to obtain robust nanostructures. Herewith, we use mixtures of oppositely-charged porphyrins that can act as mesogens to form chromonic liquid crystals in water, i.e., molecular stacks with orientational (nematic) or positional (hexagonal) order. Electrostatic locking coupled with π–π interactions between aromatic groups within the stacks, together with inter-stack hydrogen bonding induce formation of all-organic crystalline nanofibers with high aspect ratio (a few tenths of nanometers in width but several tenths of micrometers in length) and that display branching. The nanofibers prepared from metal-free porphyrin units feature interesting optical properties, including an absorption spectrum that is different from the simple sum of the individual spectra of the components, which is attributed to a striking aggregation-induced chromism. When in contact with some polar organic solvents the materials become fluorescent, as a result of disaggregation. In a proof-of-concept, the obtained self-assembled one-dimensional (1D) materials were carbonized (yield ca. 60%) to produce nitrogen-doped carbon nanofibers that can be used as active electrode materials for energy storage applications., C. R. acknowledges the financial support from Generalitat de Catalunya (2017SGR1778 grant), and from the Spanish Ministry of Science, Innovation and Universities (CTQ2017-84998-P project). C. R. is also grateful to the Agencia Estatal de Investigación and to the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER). We thank ALBA staff for their help and support in the Synchrotron SAXS experiments performed at BL11-NCD beamline at ALBA (Spain). This work is partially supported by supported by JSPS KAKENHI Grant Number JP 16H06518 (Coordination Asymmetry), CREST JST Grant Number JPMJCR1665, and Grants-in-Aid for Scientific Research (C) Grant Number 20K05590.

Perylene tetracarboxylic acid bisimides are compounds that show intense visible light absorption and exhibit excellent chemical, photochemical and thermal stability. As such, they have been widely used as dyes and have a range of industrial applications. These dyes have also been investigated for various applications in aqueous media as chromonic liquid crystals: lyotropic systems characterised by the association of aromatic mesogenic cores into stacked structures. In this study, we focus on one perylene dye bis-(N,N-diethylaminoethyl)perylene-3,4,9,10-tetracarboxylic diimide dihydrochloride, PER, and study its self-assembly in aqueous solution through both atomistic and coarse-grained molecular models. All-atom molecular dynamics simulations demonstrate spontaneous self-assembly into chromonic H-aggregate stacks with an interparticle twist between molecules. The coarse-graining of complex chromonic mesogens introduces a wealth of subtle complexities that presents a significant challenge to overcome. Consequently, we developed coarse-grained (CG) models using both bottom-up and top-down approaches: the multiscale coarse-graining method (MS-CG) in the form of hybrid force matching (FM) and the MARTINI 3 force field, respectively. We discuss the successes/deficiencies of these approaches and introduce changes to improve upon their performance and representability. For the MARTINI 3 model, careful optimisation of parameters allows it to exactly reproduce the atomistic self-assembly behaviour including the relevant thermodynamic properties in solution. The bottom-up CG model, produced using a conventional MS-CG treatment, fails to reproduce most of the target properties, but the implementation of the potentials into a combined FM-MARTINI 3 framework allows the recovery of the correct self-assembly behaviour in solution.

Lyotropic chromonic liquid crystals (LCLCs) are a special type of hierarchical material in which self-assembled molecular aggregates are responsible for the formation of liquid crystal phases. Thanks to its unusual material properties and bio compatibility, it has found wide applications including the formation of active nematic liquid crystals. Recent experiments have uncovered tumbling character of certain LCLCs. However, how tumbling behavior modifies structure and flow in driven and active nematics is poorly understood. Here, we rely on continuum simulation to study the interplay of extensile active stress and externally driven flow in a flow-tumbling nematic with a low twist modulus to mimic nematic LCLCs. We find that a spontaneous transverse flow can be developed in a flow-tumbling active nematic confined to a hybrid alignment cell when it is in log-rolling mode at sufficiently high activities. The orientation of the total spontaneous flow is tunable by tuning the active stress. We further show that activity can suppress pressure-driven flow of a flow-tumbling nematic in a planar-anchoring cell but can also promote a transition of the director field under a pressure gradient in a homeotropic-anchoring cell. Remarkably, we demonstrate that the frequency of unsteady director dynamics in a tumbling nematic under Couette flow is invariant against active stress when below a threshold activity but exhibits a discontinuous increase when above the threshold at which a complex, periodic spatiotemporal director pattern emerges. Taken together, our simulations reveal qualitative differences between flow-tumbling and flow-aligning active nematics and suggest potential applications of tumbling nematics in microfluidics.

Lyotropic chromonic liquid crystals are water-based materials composed of self-assembled cylindrical aggregates. Their behavior under flow is poorly understood, and quantitatively resolving the optical retardance of the flowing liquid crystal has so far been limited by the imaging speed of current polarization-resolved imaging techniques. Here, we employ a single-shot quantitative polarization imaging method, termed polarized shearing interference microscopy, to quantify the spatial distribution and the dynamics of the structures emerging in nematic disodium cromoglycate solutions in a microfluidic channel. We show that pure-twist disclination loops nucleate in the bulk flow over a range of shear rates. These loops are elongated in the flow direction and exhibit a constant aspect ratio that is governed by the nonnegligible splay-bend anisotropy at the loop boundary. The size of the loops is set by the balance between nucleation forces and annihilation forces acting on the disclination. The fluctuations of the pure-twist disclination loops reflect the tumbling character of nematic disodium cromoglycate. Our study, including experiment, simulation, and scaling analysis, provides a comprehensive understanding of the structure and dynamics of pressure-driven lyotropic chromonic liquid crystals and might open new routes for using these materials to control assembly and flow of biological systems or particles in microfluidic devices.

Significance A material’s topology is more than its shape. It governs the material’s physical properties, such as how it interacts with acoustic waves and transports charge carriers. Utilizing liquid crystals (LCs) and their defects, researchers have pursued understanding topological aspects of condensed matter. Our work discusses the topological properties of cholesteric LCs that twist spontaneously. The traditional topological descriptions of LC do not extend to a complete characterization of cholesterics, and yet they often exhibit behavior with a strong topological and geometric character. We show that a more subtle chiral topology, protected by nonvanishing twist, can be used to define new topological numbers and understand these systems’ behavior, including the metastability, layering transitions, and soliton structures that traditional invariants cannot describe.

A striking feature of lyotropic chromonic liquid crystals confined in cylinder model exhibit double-twist director configurations. Evidence suggests that saddle-splay deformation is among t...

As a preparation method for organic–inorganic or mesoporous inorganic materials via sol–gel condensation of a metal alkoxide, the combination of lyotropic liquid crystals (LLCs) and sol–gel chemistry is a versatile tool to fabricate various nanostructures. Despite previous investigations into such systems, no attempt has been made to utilize the dynamic switching functions of such nanostructures via the phase transition of LLCs in films. A polysiloxane containing an amine-hydrochloride group and a vinyl group was recently synthesized. By controlling the relative humidity, we achieved the phase transition of LLCs and on-demand UV-curing of LLC phases in the polysiloxane film. We further developed vertically oriented organic–inorganic nanochannels by using π−π interactions between discotic molecules and the substrate surface or the spontaneous vertical alignment of LLC containing azobenzene units. A method to control on-demand phase transition and alignment of organic–inorganic hybrid containing lyotropic liquid crystals (LLCs) have been developed. By using polysiloxane containing hygroscopicity and photocrosslinking groups, the phase transition of the LLCs can be induced by changes in humidity. The phase-transition behavior of the LLCs in polysiloxane can be suppressed by light irradiation. Further, the author proposed new methods for vertically aligning nanochannels by using surface interaction or the spontaneous vertical-aligned nature, and photopatterning of chromonic dye aggregates.

The nematic (chromonic N) and isotropic phases formed by aqueous solutions of a perylene dye are investigated by x-ray diffraction and visible light absorption spectroscopy. X-ray diffracti...

Amplification of chirality across length scales is a key concept pertinent to many models aiming to unravel the origin of homochirality. Tactoids of lyotropic chromonic liquid crystals formed by DNA, dyes, and other flat ionic molecules in water in the biphasic nematic + isotropic regime turn out to be a particularly relevant system to investigate chirality transfer and amplification. Herein, we present experiments to determine the amplification of chirality by luminescent gold nanoclusters decorated with adenosine monophosphate inducing chiral nematic tactoids formed by disodium cromoglycate in water. Polarized optical microscopy investigations of the induced homochiral tactoids reveal that adenosine monophosphate shows a higher optical activity when bound to the surface of such gold nanoclusters in comparison to free adenosine monophosphate, despite a three-time lower overall concentration. Free adenosine monophosphate also induces the opposite chiral twist both in the bulk nematic phase as shown by induced thin film circular dichroism spectropolarimetry and in the tactoids in comparison to adenosine monophosphate bound to the gold nanocluster. Overall, these experiments demonstrate that lyotropic chromonic liquid crystal tactoids are powerful systems to image and quantify chirality amplification by key biological chiral molecules that would have played a role in the origin of homochirality.

We study equilibrium configurations of hexagonal columnar liquid crystals in the context of characterizing packing structures of bacteriophage viruses in a protein capsid. These are viruses that infect bacteria and are currently the focus of intense research efforts, with the goal of finding new therapies for bacteria-resistant antibiotics. The energy that we propose consists of the Oseen–Frank free energy of nematic liquid crystals that penalizes bending of the columnar directions, in addition to the cross-sectional elastic energy accounting for distortions of the transverse hexagonal structure; we also consider the isotropic contribution of the core and the energy of the unknown interface between the outer ordered region of the capsid and the inner disordered core. The problem becomes of free boundary type, with constraints. We show that the concentric, azimuthal, spool-like configuration is the absolute minimizer. Moreover, we present examples of toroidal structures formed by DNA in free solution and compare them with the analogous ones occurring in experiments with other types of lyotropic liquid crystals, such as food dyes and additives.This article is part of the theme issue ‘Topics in mathematical design of complex materials’.

An extensive experimental study of the shapes of two-dimensional bipolar droplets of the chromonic N nematic phase of disodium cromoglycate (DSCG) sandwiched between glass plates, by Y.-K. Kim et al. was published in [Y.-K. Kim et al., J. Phys.: Condens. Matter 25, 404202 (2013)]. The paper includes a mathematical model of this system. We have extended this study by further theoretical modelling. Our results are in good, quantitative agreement with the experimental data. The model has produced what promises to be a more accurate estimate for the isotropic surface ten- sion at the nematic/isotropic solution interface—and predicts a regime of shape bistability (which has not yet been observed) for larger droplets, where tactoids (pointed, zeppelin-shaped droplets) and smooth-edged discoids can coexist in equilibrium. The general method presented in this paper is also applied to the tactoids formed by F-actin filaments in solution, for which an estimate is given for the value of the isotropic surface tension at the nematic/isotropic interface.

Cyanine dyes are known to form large-scale aggregates of various morphologies via spontaneous self-assembly in aqueous solution, akin to chromonic liquid crystals. Atomistic molecular dynamics simulations have been performed on four cyanine dyes: pseudoisocyanine chloride (PIC), pinacyanol chloride (PCYN), 5,5’,6,6’-tetrachloro-1,1’,3,3’- tetraethylbenzimidazolylcarbocyanine chloride (TTBC) and 1,1’-disulfopropyl-3,3’-diethyl-5,5’,6,6’- tetrachloro-benzimidazolylcarbocyanine sodium salt (BIC). Simulations employed an optimised general AMBER force field and demonstrate the organisation of the dyes into stacked structures at dilute concentrations. The thermodynamics of self-assembly was studied by calculating potentials of mean force for n-mers (n = 2, 3 or 4), from which the free energies of association are determined. We report binding free energies in the range of 8 to 15 kBT for dimerisation, concordant with typical values for ionic chromonics (7 to 14 kBT), and examine the enthalpic and entropic contributions to the aggregation process. The self-assembly of these dyes yields two distinct classes of structures. We observe the formation of H-aggregate stacks for PCYN, with further complexity in these assemblies for PIC; where the aggregates contain shift and Y junction defects. TTBC and BIC associate into a J-aggregate sheet structure of unimolecular thickness, and is composed of a brickwork arrangement between molecules. These sheet structures are characteristic of the smectic chromonic mesophase, and such assemblies provide a route to the emergence of nanoscale tubular architectures.

The elastic and viscous properties of lyotropic chromonic liquid crystals have a very sharp, often exponential temperature dependence. Self-propelled bacteria swimming in this viscoelastic medium induce director deformations which can strongly influence their velocity, and we study the temperature behavior of their motility in the whole range of the nematic phase. We observe experimentally that, with increasing temperature, while the viscosity drops exponentially and the frequency of the flagellum rotation grows linearly, the swimmers' speed first conventionally increases but then, above some crossover temperature, slows down and at the same time bacteria-induced director distortions become visible. It is shown that the physics behind this temperature-driven effect is in a sharp rise in the ability of the bacterium's flagellum to induce director deformations. As temperature increases, the splay and bend elastic constants sharply decrease and the anchoring extrapolation length of the flagellum surface gets shorter and shorter. At the crossover temperature the resulting effective anchoring effect dominates the fast dropping viscosity and the distortion strengthens. As a result, a fraction of the torque the flagellum applies for the propulsion is spent for the elastic degrees of freedom, which results in a bacterium slowdown. To find the director distortions, the flagellum is presented as a collection of anchoring-induced elastic monopoles, and the bacterium velocity is found from the balance of the energy spent for the propulsion and the viscous drag and nematodynamic dissipation.

We describe the influence of competing self-organizing phenomena on the formation of cholesteric mesophase in liquid crystalline brush block terpolymers (LCBBTs) and liquid crystalline random brush terpolymers (LCRBTs) containing chromonic molecules. A library of LCBBTs and LCRBTs are synthesized using ring-opening metathesis polymerization (ROMP) of norbornene side-chain functionalized monomers comprising cholesteryl mesogen (NBCh9), chromonic xanthenone (NBXan), and poly(ethylene glycol) (NBMPEG). Compression molded films of LCRBTs containing chromonic molecules display multilevel hierarchical structure in which cholesteric mesophase co-exists with π–π stacking of the chromonic mesophase along with PEG microphase segregated domains. This is unexpected as conventional LCBCPs and LCBBCs that lack chromonic molecules do not form cholesteric mesophases. The presence of π–π interactions modifies the interface at the IMDS so that both chromonic and cholesteric mesophases coexist leading to the manifestation of cholesteric phase for the first time within block architecture and is very reminiscent of previously published LCRBCs without chromonic molecules. The key to the observed hierarchical assembly in these LCBBTs containing chromonic molecules lies in the interplay of LC order, chromonic π–π stacking, PEG side chain microphase segregation, and their supramolecular cooperative motion. This unique “single component” polymer scaffold transforms our capacity to attain nanoscale hierarchies and optical properties from block architecture similar to nanoscale mesophases resulting in random architecture.

The two main classes of liquid crystals are thermotropic (containing no solvent) and lyotropic (containing solvent). Both of these classes possess the nematic phase, the most simple of liquid crystal phases with only uniaxial orientational order. For both of these classes, if the constituent molecules are chiral or if a chiral dopant is added, the preferred direction of orientation rotates in helical fashion in what is called the chiral nematic phase. Recent research has shown that because the ordering entities of the two classes are quite different (molecules versus molecular assemblies), important differences in the properties of the nematic phase can result. While thermotropic chiral nematics have been extensively examined, less is known about lyotropic chiral nematics, especially for the most ideal case, a chiral–racemic system. Furthermore, none of the lyotropic chiral–racemic studies has included lyotropic chromonic liquid crystals, which are solutions of dyes, drugs, and nucleic acids. Inverse pitch measurements are reported for a chiral–racemic system of a chromonic liquid crystal across the entire chiral fraction range and over a 30 °C temperature interval. The inverse pitch depends linearly on chiral fraction and decreases with increasing temperature, indicating that achiral and chiral molecules participate in the assembly structure similarly. The helical twisting power is significantly larger than for other chiral lyotropic liquid crystals due to the very high scission energy of the investigated system.

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.

Perylene dyes have applications in many fields. Herewith, we report on the synthesis and properties of a series of PEGylated perylene bisimides with varying PEG chain lengths. Such molecules are formed by a hydrophobic perylene core functionalized at the imide positions with hydrophilic non-ionic functional groups, which impart solubility and capacity to self-assemble in water. The diluted solutions of the synthesized molecules show interesting optical and fluorescent properties that depend on solvent and concentration; they also show surface activity and a lower critical solution temperature. Moreover, at high concentrations, the molecules produce lyotropic chromonic liquid crystals with nematic and hexagonal structures, formed by aligned molecular stacks. Such mesostructures were successfully exploited for the preparation of hybrid silica materials with ordered perylene nanostripes that generate aligned nanopores (of ca. 1.4 nm) upon calcination. It was found that the distance between perylene nanostripes and hence the pore wall thickness can be finely tuned by changing the length of the PEG chain., The authors acknowledge the financial support from the Spanish Ministry of Science and Innovation (CTQ2017-84998-P project), Agencia Estatal de Investigación, European Regional Development Fund, Generalitat de Catalunya (2017SGR01778) and Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN). Authors are grateful to Dr. Anna Aviñó, (IQAC/CSIC, Spain) and Adrián Páez, for their help in the experiments. Otherwise stated, characterization has been performed by the Nanostructured Liquid Characterization Unit, located at the Institute of Advanced Chemistry of Catalonia (IQAC), belonging to the Spanish National Research Council (CSIC) and affiliated to the NANBIOSIS ICTS of Biomedical Networking Center (CIBER-BBN), which is financed by the “Instituto de Salud Carlos III”. The authors also acknowledge the Tecnio TECCIT15-1-0009 and the “Grupo de Nanotecnología Farmacéutica” of the University of Barcelona (UB), in the Faculty of Pharmacy, which forms an Associated Unit to CSIC.

New coarse-grained models are introduced for a non-ionic chromonic molecule, TP6EO2M, in aqueous solution. The multiscale coarse-graining (MS-CG) approach is used, in the form of hybrid force matching (HFM), to produce a bottom-up CG model that demonstrates self-assembly in water and the formation of a chromonic stack. However, the high strength of binding in stacks is found to limit the transferability of the HFM model at higher concentrations. The MARTINI 3 framework is also tested. Here, a top-down CG model is produced which shows self-assembly in solution in good agreement with atomistic studies and transfers well to higher concentrations, allowing the full phase diagram of TP6EO2M to be studied. At high concentration, both self-assembly of molecules into chromonic stacks and self-organisation of stacks into mesophases occurs, with the formation of nematic (N) and hexagonal (M) chromonic phases. This CG-framework is suggested as a suitable way of studying a range of chromonic-type drug and dye molecules that exhibit complex self-assembly and solubility behaviour in solution.

Lyotropic chromonic liquid crystals (LCLCs) represent aqueous dispersions of organic disk-like molecules that form cylindrical aggregates. Despite the growing interest in these materials, their flow behavior is poorly understood. Here, we explore the effect of shear on dynamic structures of the nematic LCLC, formed by 14 wt% water dispersion of disodium cromoglycate (DSCG). We employ in situ polarizing optical microscopy (POM) and small-angle and wide-angle X-ray scattering (SAXS/WAXS) to obtain independent and complementary information on the director structures over a wide range of shear rates. The DSCG nematic shows a shear-thinning behavior with two shear-thinning regions (Region I at [small gamma, Greek, dot above]1 s-1 and Region III at [small gamma, Greek, dot above]10 s-1) separated by a pseudo-Newtonian Region II (1 s-1[small gamma, Greek, dot above]10 s-1). The material is of a tumbling type. In Region I, [small gamma, Greek, dot above]1 s-1, the director realigns along the vorticity axis. An increase of [small gamma, Greek, dot above] above 1 s-1 triggers nucleation of disclination loops. The disclinations introduce patches of the director that deviates from the vorticity direction and form a polydomain texture. Extension of the domains along the flow and along the vorticity direction decreases with the increase of the shear rate to 10 s-1. Above 10 s-1, the domains begin to elongate along the flow. At [small gamma, Greek, dot above]100 s-1, the texture evolves into periodic stripes in which the director is predominantly along the flow with left and right tilts. The period of stripes decreases with an increase of [small gamma, Greek, dot above]. The shear-induced transformations are explained by the balance of the elastic and viscous energies. In particular, nucleation of disclinations is associated with an increase of the elastic energy at the walls separating nonsingular domains with different director tilts. The uncovered shear-induced structural effects would be of importance in the further development of LCLC applications.

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.

Some industrial uses of living cells involve genetic engineering or modification of cell’s external properties. However, these techniques commonly have high financial costs, do not take advantage of the natural properties of the cells, and have few applications in the photonics area. As the first technological application of living liquid crystals, we propose an all-passive optical diode using Bacillus subtilis, chromonic liquid crystal, and silver nanorods. These three elements comprise a living liquid crystal doped with nanorods that produces a spatial inversion asymmetric system, facilitating the passage of light in one direction and hampering it in the opposite one. Solving Maxwell’s equation numerically for this system, we found optical rectification for light’s intensity up to $$1700\%$$. Such diodes can be the primary units for an all-passive optical film and other nonreciprocal systems.

Spherical confinement of nematic liquid crystals leads to the formation of equilibrium director field configurations that include point and line defects. Driving these materials with flows or dynamic fields often results in the formation of alternative metastable states. In this article, we study the effect of magnetic field alignment, both under static and dynamic conditions, of nematic gems (nematic droplets in coexistence with the isotropic phase) and emulsified nematic droplets of a lyotropic chromonic liquid crystal. We use a custom polarizing optical microscopy assembly that incorporates a permanent magnet whose strength and orientation can be dynamically changed. By comparing simulated optical patterns with microscopy images, we measure an equilibrium twisted bipolar pattern within nematic gems that is only marginally different from the one reported for emulsified droplets. Both systems evolve to concentric configurations upon application of a static magnetic field, but behave very differently when the field is rotated. While the concentric texture within the emulsified droplets is preserved and only displays asynchronous oscillations for high rotating speeds, the nematic gems transform into a metastable untwisted bipolar configuration that is memorized by the system when the field is removed. Our results demonstrate the importance of boundary conditions in determining the dynamic behavior of confined liquid crystals even for configurations that share similar equilibrium bulk structures.

Unraveling the mechanisms of packing of DNA inside viral capsids is of fundamental importance to understanding the spread of viruses. It could also help develop new applications to targeted drug delivery devices for a large range of therapies. In this article, we present a robust, predictive mathematical model and its numerical implementation to aid the study and design of bacteriophage viruses for application purposes. Exploiting the analogies between the columnar hexagonal chromonic phases of encapsidated viral DNA and chromonic aggregates formed by plank-shaped molecular compounds, we develop a first-principles effective mechanical model of DNA packing in a viral capsid. The proposed expression of the packing energy, which combines relevant aspects of the liquid crystal theory, is developed from the model of hexagonal columnar phases, together with that describing configurations of polymeric liquid crystals. The method also outlines a parameter selection strategy that uses available data for a collection of viruses, aimed at applications to viral design. The outcome of the work is a mathematical model and its numerical algorithm, based on the method of finite elements, and computer simulations to identify and label the ordered and disordered regions of the capsid and calculate the inner pressure. It also presents the tools for the local reconstruction of the DNA "scaffolding" and the center curve of the filament within the capsid.

Lyotropic chromonic liquid crystals (LCLCs) are formed by linear stacks of disc-shaped molecular in water. Combined by weak, non-covalent forces, these aggregates are reversible, flexible and polydisperse. The self-assembly nature of the basic building units gives nematic LCLCs interesting physical properties, such as very small twist K2 constant as compared with splay K1 and bend K3 constants, very large splay ηsplay and twist ηtwist viscosities, strong temperature dependence of K1, ηsplay, and ηtwist, diverse responses to different ionic additives, and large and azimuthally asymmetric disclination cores. We discuss our experimental studies on the viscoelastic properties and the fine structure of disclinations of LCLCs and attribute their unusual properties to the fact that LCLC aggregates are not fixed in size, but vary in response to changes of temperature, concentration and ionic content in the system. We further use these properties to explain intriguing phenomena in the ‘living liquid crysta...

We demonstrate that the phase diagram of a Lyotropic Chromonic Liquid Crystal (LCLC) is affected by ultraviolet (UV) light irradiation. UV-irradiation induces a phase transition from the nematic (N) to isotropic (I) state at a fixed temperature. Birefringence measured in-situ decreases under irradiation, until the moment when the isotropic phase starts to nucleate and the initial homogeneous nematic transforms into a biphasic state. On further irradiation the birefringence of the N fraction of the biphasic I-N state increases revealing redistribution of the composition components between the two coexisting phases. The efficiency of the irradiation-induced changes depends on the orientation of the chromonic aggregates w.r.t. the polarization of UV light. Changes of the birefringence are noticeably higher for light polarization perpendicular to the nematic director. The effect can be understood as a photo-induced weakening of the face-to-face molecular attraction within the chromonic aggregates and the resulting shortening of these aggregates.

Temperature and composition effects in Sunset Yellow FCF (SSY) aqueous solutions were studied by the 1H, 15N NMR as well as Raman spectroscopy passing through all phase transitions between isotropic phase (I) and chromonic phases—nematic (N) and columnar (M). It was shown that the tautomeric equilibrium in SSY is strongly shifted toward the hydrazone form. The corresponding equilibrium constant pKT = 2.5 was deduced using the density functional theory solvent model density model. The dominance of the hydrazone form was confirmed experimentally using the long-range 1H–15N correlation, widely known as heteronuclear multiple bond correlation. The peak found in the 1H NMR spectra at ca. 14.5 ppm can be attributed to the proton in the intramolecular N–H···O bond. The existence of this signal shows that (i) the growth of the SSY aggregates is accompanied by the segregation of water in the intercolumnar areas with no access for exchange with the N–H protons in the internal layers of the columnar stacks and that ...

We investigated the pitches of cholesteric liquid crystals prepared by mixing disodium cromoglycate (DSCG) in water with 5 different water-soluble chiral additives. The measurements are based on the Grandjean-Cano wedge cell method. Overall, the twisting effect is weak, and the shortest pitch of 2.9 ± 0.2 μm is obtained using trans-4-hydroxy-l-proline, by which the cholesteric sample is iridescent at certain viewing angles. Freeze-fracture transmission electron microscopy (FFTEM) was also performed for the first time on both the nematic and cholesteric phases, revealing that stacked chromonic aggregates are very long, up to a few hundred nm, which explains why cholesteric chromonic liquid crystals hardly have pitches in the visible wavelength region.

Lyotropic chromonic liquid crystal has great application potential in the areas of the biology, medicine, and optics due to its biocompatibility, nontoxicity, biodegradability and birefringence. The rotating magnetic field method was used to measure the rotational viscosity of nematic Sunset Yellow, disodium cromoglycate and Sunset Yellow doping of magnesium sulfate, sodium chloride and sodium hydroxide at various temperatures and concentrations. The rotational viscosity of nematic lyotropic chromonic liquid crystals is positively correlated with the square of the average length of columnar aggregates, increasing with the increase of concentration, but decreasing exponentially as temperature increases. This paper established a universal empirical expression of the rotational viscosity of nematic lyotropic chromonic liquid crystals and presented that the largest relative deviation between theoretical calculation and experimental results is only 22.60%. The rotational viscosity of nematic lyotropic chromonic liquid crystals becomes intensive with the increasing of magnesium sulfate and sodium chloride concentrations, while it reduces with the increase of sodium hydroxide concentration. The “one-step method” is proposed here that one sample of nematic LCLCs at various temperatures can replace normal materials to evaluate the influences of the shape anisotropy of molecules or colloidal particles on the research target, such as physical property parameters, depletion interaction potentials, and so on. This method is based on the self-assembly ability difference of lyotropic chromonic liquid crystal molecules at various temperatures and has been proved to be reliable by comparison with the results obtained from many samples of nematic 5CB, CBP5, 5PCB, et al.

Motivated by recent experiments, the isotropic–nematic phase transition in chromonic liquid crystals is studied. As temperature decreases, nematic nuclei nucleate, grow and coalesce, giving rise to...

Transfer of chirality from an adsorbed molecule to a metal nanoparticle surface, and from the resulting chiral nanoparticle to its surroundings, depends on numerous factors - structure of the adsorbed molecule, its size and shape, and its interactions with its specific environment - but is often difficult to understand and even more difficult to measure, visualize, and quantify. We examine if chirality at the nanoscale (i.e. in gold nanoparticles capped with chiral ligand molecules) is uniquely able to generate more intense responses than their organic chiral counterparts in soft condensed matter utilizing lyotropic chromonic liquid crystals (LCLCs) forming the nematic phase. As a powerful manifestation of nanoscale chiral amplification, we show that L-cysteine capped gold nanoparticles induce a tighter chiral twist within, and similar among, stacks of nematic LCLCs with several orders of magnitude fewer chiral L- cysteine ligands in comparison to the free molecular L-amino acid.

Two top-down coarse-grained molecular simulation models for a chromonic liquid crystal, 3,6,7,10,11-hexa-(1,4,7-trioxa-octyl)-triphenylene, are tested. We use an extension of the well-known MARTINI model and develop a new coarse-grained model based on statistical associating fluid theory (SAFT)-γ perturbation theory. For both models, we demonstrate self-assembly in the isotropic phase of the chromonic and we test the effectiveness of both models in terms of the structures of the chromonic aggregates that are produced in solution and the thermodynamics of association. The latter is tested by calculations of the potential of mean force for dimers in solution, which measures the strength of molecular association. SAFT-γ provides valuable insights into the thermodynamics of assembly. Exploration of a range of interactions between unlike sites demonstrates that chromonic self-assembly only occurs in a small parameter space where the hydrophilic–lipophilic balance between aromatic core and ethylene oxide chains is optimal. Outside of this balance, chromonic self-assembly is replaced by the formation of conglomerates of molecules or short stacks.

Recently, the emergence of spontaneous reflection-symmetry-broken configurations in achiral chromonic liquid crystals confined in cylindrical capillaries with homeotropic anchoring at the cylinder walls was reported, namely, the so-called twisted-escaped radial (TER) and twisted planar polar (TPP) configurations. This new example of spontaneous reflection symmetry breaking in liquid crystals was attributed to the twist elastic modulus, which is known to be unusually small in comparison to the splay and bend moduli in the case of chromonic liquid crystals. We now report the experimental observation of reflection symmetry breaking in cylindrical capillaries in the case of a classical, achiral, and nonchromonic lyotropic liquid crystal forming a nematic phase of disklike micelles orienting homeotropically at the capillary walls. We observed the same chiral TER configuration, as well as a nonplanar twisted polar (TP) configuration. The TP configuration is characterized by two half-unit so-called twist disclinations, where the director twist around the line defects drives the formation of a double helix of the disclinations along the axis of the capillary. Additionally, there is a transverse twist between the two disclination lines with the same handedness as the axial twist. Similarities with and differences from the case of chromonic liquid crystals are discussed; in particular, we examine the conditions under which spontaneous reflection symmetry breaking occurs in the nonchromonic system. It seems that the chiral TER configuration can be stabilized by the presence of point defects.

The recent interest in lyotropic chromonic liquid crystals (LCLCs) has resulted in significant understanding of the assembly behaviour and liquid crystal properties of these water-based systems. On...

The structural characterization of the orientation and elongation under shear flow in Lyotropic Chromonic Liquid Crystals (LCLCs) molecules, Sunset Yellow FCF (SSY), was performed by in situ rheological small/wide angle X-ray scattering (Rheo-SAXS/WAXS). The X-ray measurement results clearly demonstrated that the stacked aggregates were oriented and elongated to the shear direction under shear flow. Further shear rate increase caused the enhancement in the orientation and elongation with the inter-aggregate distance constant, and then the structural change decreased implying the onset of the orientation saturation at high shear rates.

The structural evolution with the self-assembly and self-alignment progress of the typical Lyotropic Chromonic Liquid Crystals (LCLCs) molecules, Sunset Yellow FCF (SSY), was studied by time-resolved grazing-incidence wide-angle X-ray scattering (GI-WAXS). It was revealed that the SSY molecules oriented by the initial shear flow gradually assembled and was oriented by solvent evaporation. Then, the drastic progress in the assembly and orientation occurred accompanying the electrostatic interaction between the assembled aggregates.

With growth of interest in functional materials possessing highly organized and well-defined nanostructures, lyotropic mesophases have received much attention. Amphiphiles and chromogens can spontaneously construct ordered lyotropic liquid crystal (LLC) and lyotropic chromonic liquid crystal phases in both organic and inorganic solvents. The combined properties of self-organization with facile orientation and intriguing optical adjustments grant lyotropic mesophases with many potential applications, including use in coatable polarizers, micropatterned films, soft actuators, biomimetic chirophotonic crystals, and energy harvesting devices. In this review, we discuss the general concept of self-assembled lyotropic mesophases and their corresponding structural evolutions in aqueous and non-aqueous systems. Recent research progress in the investigations of polymer-stabilized LLC is also discussed.

Lyotropic chromonic liquid crystals (LCLCs) have attracted attention for their potential applications as thin-film polarizers. Although it is well reported that template-assisted method can efficiently align LCLCs for thin-film polarizers, the polarizer performance using the technique has not been well demonstrated. In this study, we report for the first time that the high-resolution (∼10 nm) pattern was found to be able to overcome the issue of dead space in the channel, and the LCLC columns were well aligned along the nanoscale array. The nanoscale array templates were fabricated by secondary sputtering lithography, and the chromonic nematic phase of the LCLC materials were prepared by dissolving the hydrogen chloride salt of bis-(N,N-diethylaminoethyl)-perylene-3,4,9,10-tetracarboxylic diimide in deionized water. A polarizing performance was observed (79.1% DOP and 29.5% TT at 475 nm) using a nanoscale array template with a high resolution (∼10 nm) and a high aspect ratio (>30). To further enhance polarizer performance, the combination of a nanoscale array template and mechanical shearing was exploited. With this combined route, an LCLC polarizer exhibiting a total transmission of 40.6% and a degree of polarization of 99.5% was obtained. Compared to mechanical shearing, nanoscale array templates were found to dominantly align highly mobile LCLCs.