The electroconvection of liquid crystals is a typical example of a dissipative structure generated by complicated interactions between convective flow, structural deformation, and the migration of charge carriers. In this study, we found that the periodic fingerprint texture in cholesteric liquid crystalline droplets propagates like a wave, under an alternating-current electric field. In this situation, flow field measurement revealed the existence of the periodic convection, travelling together with the director field. This result indicated that the wave propagation phenomenon is driven by the electroconvection.

Manipulation of materials at the microscale is crucial for evaluating the microscopic properties of soft materials. Circularly polarized optical tweezers rotate birefringent objects, which enables us to measure local viscosity and control local flow fields. Efficient rotation by the tweezers leads to applications of the rotating objects in viscous fluids. It is important to establish the relationship between the optical interactions of the birefringent objects and their inner structures to evaluate the efficiency. In this study, we used liquid crystal (LC) droplets as birefringence objects and investigated the optical torque transfer to the droplets with changes in the inner structure. As an application of the droplets, we constructed multiple LC rotator systems.

Changes in some of the molecules that make up a liquid crystal can cause an overall phase transition or orientation change. When stimulus-responsive molecules are introduced into a liquid crystal, they can induce changes in the phase and structure of the liquid crystal in response to stimuli. In this study, we prepared microcapsules (liquid crystal MCs) with such stimulus-responsive liquid crystals as shells. Liquid crystal MCs that burst in response to light and those that burst in response to pH change will be presented.

Two Schiff base mesogens, 2MBAC and 4MBAC, exhibit four liquid crystal phases, N, SmA, and two types of SmB phases, on cooling. Heat capacities of those compounds were measured by adiabatic calorimetry. Their temperature dependences of entropy were estimated from the heat capacities. We discuss the relation between the entropy and the smectic order parameter estimated from x-ray diffraction in the two compounds.

Microphase separation of polymer membranes has recently drawn considerable attention for industrial applications such as separation, purification, and transportation. Herein, we synthesized main-chain liquid crystalline block copolymers containing azobenzene and polyethylene glycol (PEG) blocks and fabricated photoresponsive films. In an atomic force microscopy (AFM) phase image, we observed lamellar structure with a spacing of 26 nm in the film. Upon exposure to UV light, the lamellar structure disappeared but was restored by irradiation with visible light.

We present the development of free-standing composite electrolyte films based on ionic liquid crystal and polymers, aimed at achieving high-frequency response electromechanical actuators. Our approach involves designing novel layered ionic liquid crystals by complexing mesomorphic phosphates with lithium salts or ionic liquids through ion-dipole interactions or hydrogen bonds. These liquid crystals, when combined with vinyl polymers, yield non-flammable composite membranes with microphase-segregated structures, exhibiting room-temperature ionic conductivities of approximately 10-4 S/cm. The composite actuators, integrated with PEDOT:PSS electrodes, demonstrate bending responses at frequencies up to 130 Hz, driven by the electric double layer formation and the redox reaction of PEDOT. Additionally, we showcase a ring-shaped haptic interface utilizing these soft actuators to provide tactile sensations upon contact with fingers.

Chiral nematic liquid crystal polymers are renowned for their distinctive optical and mechanical properties. In this study, we synthesized monodisperse chiral nematic liquid crystal polymer particles using dispersion polymerization and investigated their optical characteristics, particularly their angular-independent reflection. We measured the shifts in reflection wavelength of these particles under applied pressure. Our results revealed that the reflectance wavelength shifted from red to blue as the molecular orientation changed with increasing pressure. Additionally, we confirmed the spatial resolution of these particles as sensing materials by evaluating strain distribution. These findings indicate the potential of chiral nematic liquid crystal polymer particles as effective materials for strain sensing applications.

Chiral nematic liquid crystal elastomers exhibit wavelength-selective reflection based on their twisted molecular structure. This wavelength selectivity depends on the pitch of the helical structure, allowing the changing color of the elastomer films under stretching deformation to visualize strain. In this study, we applied compressive strain to chiral nematic liquid crystal elastomers and observed the relationship between compressive strain and reflection wavelength. Additionally, we analyzed the deformation behavior by evaluating the circular polarization selectivity of the reflected light.

We focus on the surface proton hopping conduction (SPHC) mechanism where an activation energy for proton conduction is largely reduced by decreasing the distance between SO3 groups. Our gyroid nanostructured polymer film (Film-G), having a hydrophilic surface where SO3 groups are aligned densely and precisely, shows high proton conductivity on the order of 10-2 S cm-1 when the water content is about 15 wt%. We have revealed that the high proton conductivity of Film-G is attributed to the exhibition of extremely-fast SPHC mechanism due to the reduced activation energy barrier along the gyroid minimal surface.

To examine whether the LC nature of active layer materials is useful for obtaining polymer-based OFETs with high operational stability, OFETs with active layers of PBTTT and PCDTPT were fabricated with nearly identical device structures. Here, PBTTT and PCDTPT are LC and non-LC materials, respectively. To minimize the experimental uncertainty, their bias-stress effects were evaluated under the same bias-stress condition and vacuum environment. The PBTTT-OFETs exhibited higher stability than the PCDTPT-OFETs. However, the difference in the stability was found to be in the flat-band voltage shift, which is related not to the LC nature but to the ionization potential of the active layers. Therefore, the positive correlation between the operational stability and the LC nature could not be confirmed.

Ferroelectric liquid crystal based on a quinquethiophene core bearing lactate moieties was synthesized for an improvement of a bulk photovoltaic effect in the ferroelectric liquid crystal phase. The quinquethiophene derivative exhibited bulk photovoltaic effect in the ordered chiral smectic phase where the liquid crystal molecules tilted from the layer normal. For PCBM-doped compound 1, the open-circuit voltage was 0.72 V and the short-circuit current was 270 μAcm−2, for white light illumination (2.4 mWcm−2) resulting in the improvement of the power conversion efficiency to 0.7%.

We have successfully fabricated cholesteric liquid-crystalline (CLC) semiconductor thin films from the mixture of dimeric and monomeric compounds based on oligo(p-phenylenevinylene) units by spin-coating method. This is the first example of solution-processed planarly orientated thin film in CLC semiconductors. The mixture exhibited a stable CLC phase at lower temperatures than the compound alone, allowing the fabrication of spin-coated CLC thin films at room temperature. Furthermore, the dimeric compound has trifluoromethyl groups that exhibited high solubility in organic solvents such as chloroform due to its improved hydrophobicity. In addition, the high hydrophobicity of the trifluoromethyl groups lowers the surface tension of the liquid-crystal material, resulting in planar orientation.

Poly(phenylacetylene)s have a rigid main chain. These main chains have stereo-regularity due to the polymerization mechanisms, which results helical structure is formed in the main chain. The helical structure can be induced by chiral substituents or guests. We have been developing the chiral materials such as chiral stationary phases, scaffolds for asymmetric catalysts, and spin-selective materials by taking advantage of this feature. In this presentation, I will present our recent studies on the controlled polymerization reaction mechanism of phenylacetylene and the application of precisely synthesized polymers to functional chiral materials.

We describe a weak azimuthal anchoring (WA) alignment technique to realize a low-power IPS LCD. This mode has a problem of slow response time of liquid crystal. By using the horizontal virtual boundary, we have achieved that the response time is less than 4ms in WA cell.

The most effective way to obtain display visibility in ambient situations is to suppress the reflectance of the display. After analyzing the factors contributing to unwanted reflection, specific layers were identified that required improvement. Subsequently, these elements were carefully optimized, resulting in a significant reduction of internal reflection to 0.32% for our 7” FFS-mode prototype, compared to 0.96% in conventional LCDs and it has been demonstrated to provide excellent visibility in bright ambient conditions while allowing for reduced backlight brightness and lower power consumption.

The orientation order of nematic liquid crystal elastomers (NLCEs) can be modulated by heat or light, resulting in light induced stress and shape changes. The stress changes in several NLCEs under various applied strains will be discussed.

Conventional optical microscopes visualize static inhomogeneities such as orientation, concentration, and density inside materials. The "Fluctuation Microscope" we have invented and developed is a new microscope that can visualize "dynamic inhomogeneity," the internal spatio-temporal structure of matter, as 2D still and moving images on scales from nano to meso. Thus, fluctuation microscopy is a powerful new microscopy tool that allows us to observe essentially new types of dynamic images that have never been seen before in any material system, including research, development, manufacturing, nature, and living organisms. For example, it can be used to observe optically transparent liquid products such as alcoholic beverages, cosmetics, and food products.

I am conducting research on a method to solve the crystallographic phase problem and determine the electron density distribution from diffraction measurements of liquid crystal bicontinuous phases, represented by the gyroid phase, which have three-dimensional periodicity. From the characteristics of the electron density of the liquid crystal bicontinuous phase, I have already demonstrated that two indicators are effective in evaluating the correctness of the electron density (or crystallographic phase). Here, I report a method of using the volume fraction of high and low electron density regions within the liquid crystal molecules as an indicator for evaluating electron density.

We here report the development of organic/inorganic hybrid liquid-crystalline (LC) materials consisting of a hydroxyapatite (HAP)/poly(acrylic acid) (PAA) nanorod and photoresponsive dendritic forklike mesogens. New forklike mesogens containing three azobenzene moieties are designed and synthesized for the surface modification of the HAP/PAA nanorod with these molecules. The HAP/PAA nanorod modified with the forklike mesogens exhibits thermotropic LC phases and photoresponsive properties in the solvent-free states. The biomineral-based photoresponsive organic/inorganic colloidal liquid crystals may have potential for the development of new photofunctional sustainable materials.

Nanopore materials with fluidity show promise for novel chemical events such as the accommodation, unique arraying, and chemical reactions of guest molecules, which could potentially lead to new insights and developments in this field. It appears that columnar liquid crystals composed of shape-persistent macrocycles may form nanochannels due to the intrinsic nanospace in the column. However, the existence of substantial nanoporosity has not been investigated experimentally. In this study, we confirmed the presence of discrete and spatiotemporally continuous voids in a liquid-crystalline material using 129Xe NMR spectroscopy.

Axially polar-ferroelectric columnar liquid crystals (FCLC), which can respond to an external electric field and maintain the change, have been expected to be applied to ultrahigh-density memory devices. However, in practical use, achieving an FCLC at room temperature (RT-FCLC) is desired. In this study, to exhibit RT-FCLCs, we designed a new molecule possessing two ester linkers at the outer part of its core moiety. It was expected that intermolecular dipole-dipole repulsion between the ester linkers allows the generation of LC phases, lowers the LC temperature range, and makes the electro-response easier. In conclusion, introducing the two ester moieties suppressed the molecules from packing tightly, and the compound achieved RT-FCLC.

We have developed a Correlated Disorder Model (CDM) for the charge transport properties of liquid crystalline organic semiconductors. In this study, we introduced a degree of correlation for charge transport in liquid crystals that depends on the arrangement and orientation of the molecules. We found that the field dependence of mobility for several model molecules can be explained by our CDM for different phases of liquid crystal.

Charge-transfer complexes formed by donor and acceptor molecules are expected to be applied to N-channel organic transistors. In this study, we have proposed a new method of preparing charge-transfer complex thin films by stacking donor and acceptor molecules, thermally annealing them, and diffusing acceptor molecules into the donor thin film. Benzothienobenzothiophene derivatives were used as donor molecules and tetracyanoquinodimethane derivatives as acceptor molecules, and the stacked structures were formed and thermally annealed. The crystal structure of the thin film showed that a charge-transfer complex thin film was formed, and N-channel transistor operation was also realized.

Imparting fluorescent properties to liquid-crystalline (LC) materials is one of the most promising approaches to creating fluidic fluorescent materials that can be applied to flexible devices. Our recent studies revealed that difluorinated tolane derivatives with an imidazolium bis(trifluoromethane)sulphonate-terminated decyleneoxy chain exhibited a SmA phase at around room temperature and a blue fluorescence in the SmA phase. In this study, tetrafluorinated tolane-based photoluminescent LCs were synthesized and their LC and PL properties were investigated to obtain stronger fluorescence under the LC phase. As a result, an increase in fluoro-substituents significantly weakened the fluorescence, but destabilized the crystalline phase to easily form the LC phase.

We are developing of organic multifunctional devices that focus on both light-emitting and photovoltaic functions using functional organic semiconductors. In this presentation, we will introduce our resent research on organic light-emitting diodes that emit light at extremely low voltages below the photon energy by utilizing exciplexes at the donor/acceptor interface, and our results on realizing organic photovoltaic properties in the same devices.

Perovskite solar cells (PSCs) are good candidates for low-cost solar cells fabricated by the coating method with a high conversion efficiency of over 25%. In this presentation, we will introduce a method to induce and grow CsFAMA perovskite films with large particles and high crystallinity by MAPbI3 nanoparticles (NPs) by using ionic liquids (ILs) and then forming a triple cation (CsFAMA) perovskite precursor solution on the NP films for obtaining high durability. In addition, we will present a study on the atmospheric deposition of IL-doped high-durability perovskite solar cells using the bar coating method, to apply the technique to the Roll-to-Roll method.

We demonstrate the fabrication of high-quality surface alignment layers on glass using Direct Laser Writing with a 2-photon polymerisation technique. Commercial photosensitive resins are utilized to print alignment layers by scanning a femtosecond laser focal point near the resin-glass interface, resulting in ~100 nm thin layers. These layers provide good planar anchoring for nematic liquid crystals, with an easy axis of alignment along the scanning direction. The azimuthal anchoring strength is comparable to commercial rubbed polyimide layers. This method offers flexibility, enabling fast printing of complex shapes with arbitrary alignment patterns not only in 2D but also in 3D.

Here we introduce some studies on the structures caused by the various frustrations in liquid crystals.

Millimeter-wave and THz-wave regions are positioned between radio frequencies and optics within the broader electromagnetic wave spectra, which had long remained unexplored. However, they have now become crucial for wireless communication technology due to the rapid advancement of mobile communication systems. Unlike the radio frequency region, beam propagation control devices are essential for utilizing these high-frequency regions. Among many functional materials capable of achieving such devices, liquid crystals (LCs) are primary candidates due to their low loss and low power consumption. Although this potential of LCs was not recognized decades ago, another potential of LCs has been steadily investigated alongside the shining LC display development.

The orientation control of blue phase liquid crystals (BPLCs) is important for their device applications. However, due to the complex molecular arrangement, it is difficult to obtain uniform domains or giant single crystals, and appropriate orientation techniques have not yet been developed. In this study, we focus on the phase transition from cholesteric phase to BPI and find that the phase transition is induced by regions with locally increased elastic energy, such as Grandjean-Cano disclinations. We also demonstrated the control of BPI nucleation position and BPI orientation region by using this property.

We carry out a numerical study on the structural transformation between a perfectly ordered cubic cholesteric blue phase (BP), known as BP II, and another cubic BP (BP I). Our study is based on a Langevin-type equation for the dynamics of orientational order parameter of a second-rank tensor. To distinguish the local structure of BP, we resort to supervised machine learning. We successfully clarify the dynamics of the transformation to BP I with twin boundaries, initiated by the formation of a BP I nucleus. We also show that the twinned BP I transforms to a perfect BP II lattice by temperature variation.

In several cyanobiphenyl liquid crystals, the Marangoni flow under temperature gradient was measured using the fluorescence photo-bleaching method. The Marangoni flow was observed in the coexisting state of two different phases, and it was found that the flow direction changed depending on the sample and coating material on the substrate. Based on these results, we give a model that can explain the flow direction in terms of surface tension and contact angle.

The isotropic-nematic phase transition is generally a first-order phase transition. When an electric field is applied to a nematic liquid crystal with negative dielectric anisotropy, a tricritical point is theoretically predicted to appear on the temperature-electric field phase diagram. We have shown that soft mode can be observed by performing dielectric measurement under a DC electric field. In this study, we attempted to measure soft mode in nematic liquid crystal with negative dielectric anisotropy by the method proposed in our previous study. We found that a peak appears in the temperature dependence of the dielectric constant . Furthermore, we observed a Debye-type dielectric dispersion, which is considered to be contributed by the soft mode.

In nematic liquid crystals with high conductivity, turbulence with disclinations occurs when a strong electric field is applied. Furthermore, it has recently been found that the apparent viscosity becomes negative and spontaneous shear flow appears using a rotational rheometer. In this study, we show that simulations using continuum theory can reproduce the turbulence, disclinations, negative viscosity, spontaneous shear flow, and discuss the mechanism.

In this study, we investigated the control of liquid crystal convection with a spatially modulated electric field given by patterned electrodes. As a patterned electrode, a glass substrate coated with photo-etched indium tin oxide (ITO) was used, where the surface was given a hexagonal array of bare grass substrate. With a patterned electrode, we observed the oscillation in the direction of the convection roll localized at the area where the coating of ITO remained. Furthermore, we observed the oscillatory pattern showed a traveling wave, as well as a spiral and target pattern.

Ferroelectric nematic liquid crystals have garnered much attention from both fundamental and application perspectives due to their giant polarization characteristics. In this study, we designed and synthesized polar rod-like mesogens with permanent dipole moments nearly perfectly aligned with their molecular axes, resulting in the discovery of a ferroelectric heliconical nematic phase. Within this phase, the molecules possess a helical structure while being tilted relative to the helical axis, allowing for ultra-low voltage selective reflection color modulation (0.14 V/μm) Under the electric field along the helix axis.

In the chiral system competing ferroelectricity and antiferroelectricity, some subphases with narrow temperature ranges appear. In the certain binary phase diagram of chiral molecules, the transition line between ferroelectric and antiferroelectric phases becomes apparently parallel to the temperature axis at the critical concentration. In this study, we determined the structure of this region using soft resonant X-ray scattering. Furthermore, we found that the structure changes sensitively depending on the cell thickness of the liquid crystals due to the low energy barrier between the ferroelectric and antiferroelectric orders.

Ferroelectric nematic liquid crystal (FNLC) is a groundbreaking material that possesses ferroelectricity, liquid crystallinity, and high symmetry. For the application of FNLC, controlling polarization and molecular orientation is necessary, but there are many unexplored elements in the molecular orientation properties of FNLC. In this study, we focused on pretilt, which is molecular tilting at the interface, and the polarity of the alignment film as factors affecting the polarization state. We found that the presence of a pretilt, which breaks the out-of-plane symmetry at the interface, causes a remarkable difference between the two stable states at the interface, and only one state is obtained.

We report the first example of visualizing Maxwell stress perpendicular to the electric field in ferroelectric nematic liquid crystals (NF LC). Unlike conventional rigid ferroelectrics or dielectric elastomers, the fluidic NF LC underwent large deformation by the Maxwell stress under a low driving voltage, demonstrating potential applications for electrostatic actuators. Systematic analysis of both kinetic and electric data revealed that NF LC's continuous transition of paraelectricity to ferroelectricity was critical, generating large forces with an apparent threshold. The generated force was proportional to the electric field and accumulating charge on the electrode/liquid crystal interface, exemplifying an unprecedented repulsion mode of fluid ferroelectrics.

Chiral nematic liquid crystals (N* LC) have garnered significant interest for their potential in flexible circularly polarized luminescence (CPL) devices. Traditionally, the CPL properties of N* LC are limited by viewing angle constraints, as luminescence occurs predominantly along the helical axis. In this study, we address this limitation by developing omnidirectional CPL materials using N* LC polymer particles with radially oriented helical axes. These innovative particles pave the way for advanced applications of organic CPL materials, overcoming the directional dependence and enhancing device versatility.

Chiral nematic liquid crystals, which forms helically twisted molecular alignment, exhibit the distribution of refractive index along the helical axis. Controlling the helical-axis alignment enables us to express their optical properties. For instance, controlling in-plain alignment of helical axis generates a selective reflection property, whereas controlling out-plain helical-axis alignment generates a diffraction and polarization conversion properties. However, the arbitrary controlling method for the helical-axis alignment has not yet been established. Previously, we found that the helical-axis alignment was aligned in photopolymerization process with an intensity-gradient patterned light. In this study, we discussed the formation mechanism of the helical-axis alignment.

Chiral-nematic liquid crystals (N* LCs) exhibit a refractive index distribution along their helical axis. Due to their helical structure, N* LCs reflect light at wavelengths corresponding to their helical pitch. Since the helical pitch is dependent on the concentration of chiral molecules, altering this concentration can induce various reflection colors. This study aimed to create reflection color gradation in N* LC films through photogradient polymerization. A mixture of LC monomers and non-polymerizable chiral molecules was subjected to photogradient polymerization. We analyzed the reflection wavelength of the resulting polymer film and obtained insights into the spatial distribution of the helical pitch.

Self-assembled ionic liquid crystals can form various nanochannel structures with the aggregation of ionic moieties, which brings feasible features such as selective transport properties of water and ions. For understanding nanoscopic behaviors of liquid-crystalline molecules, we developed a new molecular model for ionic liquid-crystalline compounds by using quantum-chemical method in the condensed state. The structure and physical properties of ionic liquid crystals were investigated within the framework of large-scale molecular dynamics simulation, and we then revealed statistical-mechanical differences of solubility and transport properties of molecules in response to the nano-and mesoscopic structures of self-assembled ionic liquid crystals.

2-(2-Hydroxyphenyl)benzazole (HBX) derivatives are colorless and efficiently luminescent in visible region even in the aggregated state. We have developed luminescent nematic liquid crystals (LCs) by introducing particular substituents into the HBX cores. The selection guideline of these substituents for increasing the fluorescent quantum yield was established. The LC HBX derivatives showed polarized luminescence. The guest-host type LCs prepared from the newly synthesized HBX derivatives and room-temperature (chiral) nematic LCs also showed polarized luminescence, together with amplified spontaneous emission and cholesteric LC laser emission.

Supramolecular liquid crystals allow for a wider molecular design approach for liquid crystallinity expression and the creation of material functions utilizing the introduced supramolecular system nature. In this study, we report a novel supramolecular liquid crystal based on pseudo-rotaxane structures. By threading an isotropic axle molecule as a mesogen core with an isotropic ring molecule as flexible tails, the resulting [2]pseudo-rotaxane showed thermotropic liquid crystallinity. Reflecting the characteristics of pseudo-rotaxanes, which are capable of reversible association and dissociation, our supramolecular liquid crystals exhibit phase transitions involving a temperature-dependent reversible macroscopic phase separation.

We investigated the molecular assembly structures and Li-ion conductivity of lyotropic liquid crystalline polymer electrolytes by adding organic solvents commonly used in Li-ion batteries. It was found that adding a mixture of ethylene carbonate and dimethyl carbonate resulted in forming a highly crystalline organized structure and improved Li-ion conductivity due to the solvation of Li ions. Furthermore, we demonstrated that coating sulfonated polyimide thin films to the cathode of a Li-ion battery as an artificial cathode-electrolyte interface (CEI) was effective in improving capacity retention at high-rate discharge compared to the uncoated case.

In this study, we developed molecules with a phenanthroimidazole (PI) skeleton containing an imidazole moiety, expecting to investigate how the phase behavior of these molecules changes depending on the presence of guests. Two types of host skeletons, para-PI-Cn (n=2, 4, 6) and meta-PI-Cn (n=2, 4, 6), were synthesized. Neither of these hosts exhibited a liquid crystalline phase as a single host, and were in an amorphous state. On the other hand, when a small molecule with a carboxyl group was added to the host, the appearance of the Col phase was confirmed.

Alignment of the liquid crystalline polymer interacts with the conformation of the polymer backbone, and the macroscopic mechanical properties as well as the optical properties is affected. The stability and orientation of liquid crystals can be controlled by utilizing the photoresponsive property of N-benzylideneaniline, which is also expected to control adhesion and bonding properties. In this study, we introduce the modulation of adhesion and adhesion properties by utilizing the alignment control of polymer liquid crystals.