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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.

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.

Drop drying and deposition phenomena reveal a rich interplay of fundamental science and engineering, give rise to fascinating everyday effects (coffee rings), and influence technologies ranging from printing to genotyping. Here we investigate evaporation dynamics, morphology, and deposition patterns of drying lyotropic chromonic liquid crystal droplets. These drops differ from typical evaporating colloidal drops primarily due to their concentration-dependent isotropic, nematic, and columnar phases. Phase separation occurs during evaporation, and in the process creates surface tension gradients and significant density and viscosity variation within the droplet. As a result, the drying multiphase drops exhibit different convective currents, drop morphologies, and deposition patterns (coffee-rings)., When particle-laden drops evaporate, coffee ring patterns form which can affect particle deposition. Here Davidson et al. show that unlike previously investigated drops, the flows in drying drops of liquid crystals are driven by an increase in surface tension due to liquid crystal concentration.

I am drawing the readers’ attention to the importance of the kinetic energy contribution which has been systematically ignored in the partition functions of worm-like objects in a thermal bath. The kinetic energy of linear aggregates is shown to play a unique role when they are reversibly assembled from solute molecules in a solvent. The kinetic energy contribution to the partition function of an n-mer is modeled by the term nq, where q is determined by the persistence lengths of different translation-rotation modes (e.g., q = 5 for a rigid rod and q ≈ 0 for a very flexible chain). The model gives rise to different aggregation regimes for lower and higher solute concentration. The concentrations of different n-mers and total aggregate concentration, which is the main order parameter of the system, are found to depend on the solute concentration via its powers that are different in different regimes, but are always determined solely by the parameter q. The approximate analytical and numerical solutions of the model are in quantitative agreement and clearly show the universal power-law q dependencies. At the same time, it is imposible to express the exact analytical solution in a simple form. The model is pertinent to self-assemblies of plank-like dye molecules dissolved in an isotropic solvent (related to lyotropic chromonic liquid crystals).

The bisazo dye Ponceau SS forms an acute oblique (V-type) dimer in dilute aqueous solution. In concentrated aqueous solution, these V-type dimers are considered to stack to form V-type blocks of chromonic liquid-crystalline (LC) columns. The weak interactions among these LC columnar V-type blocks have been spectroscopically investigated. On increasing the concentration of Ponceau SS at 25 °C, the V-type LC columnar blocks form a rhombus-type LC columnar block at 2 wt% concentration. These rhombus-type LC columnar blocks are further aligned at an acute angle at 5 and 10 wt% concentrations. The rapidly cooled 10 wt% LC sample shows an unusually sharp J-band-like peak in the electronic absorption spectrum. The emergence of this J-band-like peak has been analyzed from the viewpoint of an exciton model, suggesting that many nearest neighbor unique molecules belonging to many different rhombus-type LC columnar blocks are aligned in a head-to-tail manner to give a giant quasi-linear head-to-tail-type exciton.

The presumed ground state of a nematic fluid confined in a cylindrical geometry with planar anchoring corresponds to that of an axial configuration, wherein the director, free of deformations, is along the long axis of the cylinder. However, upon confinement of lyotropic chromonic liquid crystals in cylindrical geometries, here we uncover a surprising ground state corresponding to a doubly twisted director configuration. The stability of this ground state, which involves significant director deformations, can be rationalized by the saddle-splay contribution to the free energy. We show that sufficient anisotropy in the elastic constants drives the transition from a deformation-free ground state to a doubly twisted structure, and results in spontaneous symmetry breaking with equal probability for either handedness. Enabled by the twist angle measurements of the spontaneous twist, we determine the saddle-splay elastic constant for chromonic liquid crystals for the first time., Chirality in molecular materials is commonly used to manipulate the polarization of light. Here, Nayani et al. observe the formation of doubly twisted structure in achiral chromonic liquid crystals when confined to a cylindrical capillary, which leads to spontaneous chiral breaking.

Having a well aligned monodomain is critical to performing fundamental studies on liquid crystals as well as exploiting them for technological applications. Unlike conventional nematics, lyotropic chromonic liquid crystals are notoriously hard to align. Here, we report on the homogeneous planar alignment of Sunset Yellow in a flat rectangular capillary. Counterintuitively, the in-plane director aligns perpendicular to the long axis of the rectangular capillary. We rationalize the evolution of this configuration from a metastable twisted configuration by considering the coupling of the curvature of the edges of the rectangle to the Frank free energy via the saddle-splay contribution.

We use a layer-by layer electrostatic assembly technique to obtain aggregates of a chromonic mesogenic dye on mica substrates. The aqueous solutions of dye used for deposition are in the nematic phase. Atomic force microscopy of the dried films reveals that the chromonic molecules adsorb at the charged substrate in the form of ordered aggregates of elongated shape. These elongated aggregates form orientationally ordered arrays. The overall orientation of the array can be changed by shear.