Resonant X-ray scattering (RXS) is sensitive to the system symmetry and is useful to analyze the precise orientation structure, which is difficult to analyze by conventional X-ray scattering. In order to enable the RXS measurement with many liquid crystal compounds, we started to perform resonance soft X-rays scattering with carbon K-edge energy. In this paper, we will show you a part of the results.

We investigated the Marangoni convection induced in the cyanobiphenyl liquid crystalline materials of 5, 6, 7 and 8CB in sandwich cells under a temperature gradient especially near transition points. We analysed the flow field near air interface by using fluorescence photo-bleaching method. In all the samples described above, we observed the appearance of the Marangoni convection, where the flow direction depended on the sample and temperature range. On the basis of these experimental results, we discuss the relation between surface tension gradient and flow field in cyanobiphenyl liquid crystals.

In the process of forming polymer network liquid crystals (PNLCs) from mixtures of liquid crystals (LCs) and reactive mesogens (RMs), the thermoresponsive behavior in orientation order of these two liquid crystal molecules was systematically and quantitatively investigated. Focusing on 6CB/RM257 mixed systems, the temperature dependence of the degree of orientation order was examined by spectroscopic measurements at different stages of photopolymerization induced phase separation (PPIPS). The molecular orientation order of the systems is thermally transformed between three phases. The two phase transition temperatures between three phases decrease and become nonuniform as PPIPS progresses.

Block copolymers that consist of multiple polymers attached by covalent bond form various nanoscale ordered morphologies by self-organization and microphase separation. Especially, block copolymers which contain liquid crystal show cylinder structure. In this study, we synthesized block copolymer comprising poly(ethylene oxide) (PEO) and liquid-crystalline trifluoro methoxy azobenzene, whose wettability can be controlled upon irradiation with light, and aim to create materials that reversibly form the cylinder structure.

Controlling method of molecular orientation in liquid-crystalline polymer (LCP) is important to develop the functional soft-materials. We achieved fabricating chiral-nematic LCP microparticles by dispersion polymerization and controlling molecular orientation. In this study, we reveal the formation mechanism of the monodomain orientation of LCP over several μm3. From various experiments, we expected that the molecular orientation was determined during the nucleation-growth process in polymer precipitation system of dispersion polymerization. The detailed formation mechanism of molecular orientation will be discussed.

Helically assembled network polymers exhibiting circularly polarized luminescence (CPL) have been synthesized in chiral liquid crystal through the photo-radical polymerizations of acrylate derivatives. The polymers showed unique optical texture similar to the chiral liquid crystals used as asymmetric polymerization reaction fields. This result indicates the polymers have helical structures based on the chiral liquid crystals. In this study, various helically assembled network polymers were synthesized through the polymerizations of different kinds of acrylate derivatives in two types of chiral nematic liquid crystal (N*-LC) systems. CPL properties of the polymer films were evaluated.

Liquid crystal elastomers, Nematic, main-chain elastomer, light diffusion, stripe domain, dynamic tunability, iridescence

The Williams domain appears in an electroconvective system of nematics under an ac voltage. When the applied voltage is increased, the Williams domain becomes unstable and fluctuates. This state is called fluctuating Williams domain. This instability is caused by the competition between the electroconvective effect and viscous torque. We describe the system size dependence of the appearance of the fluctuating Williams domain. Furthermore, we clarify the properties of the fluctuation from the conductivity and diffusion coefficient by observing the position of fine particles under external forces.

The lattice orientation of cholesteric blue phase II, which has attracted significant attention from both fundamental and practical perspectives, was investigated on stripe-patterned surfaces where the easy axis of the adjacent region changes discontinuously. When the easy axes of the adjacent patterns are orthogonal to each other, the lattice orientation depends on the patterned-region size. For a large regional period, the (110) lattice plane is parallel to the substrates, and its [001] axis is oriented corresponding to the easy axis in each region, while for a small period, owing to the orientational frustration caused by the elastic strain, the (100) plane is uniform regardless of the pattern.

Recently, we have been working on the development of π-conjugated cholesteric liquid crystal with the aim of realizing circularly polarized electroluminescence. In this study, we investigated the selective reflection and circularly polarized photoluminescence characteristics of dimer-type cholesteric liquid crystals that adopted oligo(p-phenylenevinylene) as a π-conjugated system. As the result, we observed the different circularly polarized photoluminescence characteristics between the forward and backward configurations of the detector to the excitation light. It was found that this characteristic is owing to the dense aggregation of the π-conjugated system and the disorder of the molecular orientation.

Thinning and weight reduction of lenses are important factors for miniaturization of optical equipment. A geometric phase lens based on the in-plane orientation pattern of a liquid crystal display can have a lens function with a thickness of several micrometers, so it can be expected that the lens will be thinner and lighter. In this presentation, we report on "design of geometric phase lens with aberration correction function using genetic algorithm" and "formation of geometric phase lens using photocrosslinkable polymer liquid crystal" which we have been working on in recent years.

We directly measured the three-dimensional dynamics of nematic disclination lines during the relaxation process from an electrically driven turbulent state, by using confocal microscopy and fluorescent dye accumulation on disclinations. We focused, in particular, on reconnections of disclinations. We showed the scaling law for in-plane reconnection, by which the distance between reconnecting disclinations decreases by the square root of time to the reconnection. Moreover, we revealed that reconnecting disclinations approach symmetrically, which is contrasted with asymmetric dynamics known for the two-dimensional counterpart. We discuss this symmetry restoring mechanism in terms of both topology and energy and expect it to have generality beyond liquid crystals.

A ferroelectric nematic liquid crystal (NFLC) has vast potential because of a giant dielectric permittivity (> 103), large spontaneous polarization (> 4 μC cm−2), high fluidity etc. However, it remains a big challenge to control the NF phase transition and drive the NF phase over a wide temperature range. Herein, we report a new concept based on the dipole equivalent for tuning the NF phase transition and their plausible effect on the cluster formation. Especially, we deeply discuss the alternation of the NF phase transition in terms of cybotactic cluster formation experimentally and computationally.

Cholesteric liquid crystals (CLCs) have been extensively studied for application to new optical elements due to their excellent selective reflection of light. There have been various reports on how to broaden reflection band, such as pitch gradient distribution, but here we have developed a method for penetrating a high-birefringence guest liquid crystal after preparation of a CLC polymer film. It has been confirmed that the penetration of 5CT liquid crystal can broaden the selective reflection bandwidth by about 21% with increasing pitch-length of CLC. We will also report that this method can be applied to liquid crystal diffraction gratings.

We investigate the structures of a cholesteric blue phase (BP) cell of finite thickness under an electric field. We carry out large scale numerical calculations based on the Landau-de Gennes theory describing the orientational order by a second-rank tensor. Attention is paid to the so-called BP X and the BP I, and their electrostriction is demonstrated to be such that the number of periodic structures is discretized by the anchoring of cell surfaces. We also calculate the reflectivity spectra of these BP structures to confirm the shift of the peak attributable to the electrostriction.

A metallofoldamer with aliphatic side chains exhibits thermotropic columnar liquid crystalline properties. The metallofoldamer was prepared from two homochiral crescent-shaped precursors having beta-diketonate ligands through bridging by metal complexation; it exhibited a single helicity owing to the overlapping of both ends. The precursor and metallofoldamer formed similar hexagonal columnar phases. The helical metallofoldamer exhibited the hexagonal columnar phase at the higher temperature range owing to its rigid helical mesogenic structure.

We have synthesized spin-labeled liquid crystalline compounds, one of which shows a cybotactic nematic (Ncyb) phase. X-ray diffractometry and electron paramagnetic resonance (EPR) spectroscopy of the new compound around the Ncyb phase to analyze the molecular orientation and intermolecular interactions in the phase. The results indicate that the molecules move in and out of the cybotactic cluster fast enough to average the magnetic interactions.

Hydrogen-bonded cyclic hexamers, so-called rosettes of π-conjugated molecules with barbituric acid unit undergo supramolecular polymerization in non-polar solvents through π-stacking interactions to form spontaneously (intrinsically) curved nanofibers. This intrinsic curvature enables the creation of supramolecular polymers with a variety of topologies (shapes), such as rings (toroids), helices, waves, spirals, and chains (polycatenanes). In addition, these supramolecular polymer assemblies have topology-dependent energy landscapes and also exhibit dynamic, diverse properties derived from hydrogen bonding.

The nematic liquid crystal (NLC) has truly three-dimensional fluidity because of nematogens exhibit only orientational but no positional order. The unique electro-optical effect in NLCs has led the portable computing revolution of the 20th century in the LC display technologies. In sharp contrast, a new class matter state, a ferroelectric nematic liquid crystal (NFLC), in which the local nematic director is non-degenerate, is of great fundamental interest, and its exceptional large polarization behavior as well as its high fluidity offers state-of-the-art applications challenge. In this presentation, the global trends, world-historical event including our recent achievements, on NFLCs will be introduced.

Diastereomers consisting of a styrylterthiophene-based chromophore and two lactate moieties were synthesized. These diastereomers exhibited ordered smectic crystal phases in which the chromophores tilted from and parallel to the layer normal. In the smectic crystal phase with the chromophores parallel to the layer normal, no bulk photovoltaic effect and electroluminescence were not observed while bulk photovoltaic effect and polarized electroluminescence were observed in the smectic crystal phase with the chromophores tilted from the layer normal.

Synchrotron radiation XRD technique was applied to analyze the nano-structure of the composites of a liquid crystalline semiconductor (9TNAT9) and poly(3-hexylthiophene)(P3HT), which exhibit the highest level of hole mobility for pure and well-aligned P3HT. It was indicated that an amount of 9TNAT9 resolved in P3HT surely enhances the p-p interaction among polymer backbones.

Alkylamide chains are interesting structural units in which dipole moments and conformational degrees of freedom coexist. One-dimensional chains with intermolecular N−H•••O=　hydrogen bonds can realize a polarization inversion by applying an external electric field in liquid crystals, and a hysteresis appears in the electric field-polarization curve. The combination of the alkylamide chain with the functional π-electron skeleton enables the creation of a wide variety of multifunctional materials.

Recently, we found that inorganic nanosheets in water self-assemble to form a liquid-crystalline lamellar structure with an ultra-large periodicity by controlling the interactions between the nanosheets. The resultant dispersion exhibits a vivid structural color that can be tuned by thermal stimuli. In this presentation, we will report a new type of structural color with double reflection peaks by applying a temperature gradient to the nanosheet dispersion.

Perylene bisimides (PBIs)-based molecules have attracted attention due to their excellent n-type semiconductor properties, and it is known that PBIs with alkyl side chains can construct various assembly states by π-π stacking. Here, we report PBIs with amide groups at the imide position and “branched” alkyl side chains at the end of the molecules. The PBIs showed layered, columnar, and spherical assembly depending on the number of branched side chains and carbons. Significantly, unlike PBI superstructures with linear side chains, the branching of the side chains allows stable spherical assembly over a wide temperature range, including room temperature.

I have developed tabletop ultrafast time-resolved electron diffraction setups to measure the dynamics of photoreactive or photoresponsive materials in real-time and on atomic and molecular scales. In this presentation, I will explain the ultrafast time-resolved electron diffraction measurements and describe the structural dynamics of liquid crystals. In addition, I will introduce ongoing projects on developing novel ultrafast time-resolved electron diffractometers, which will be useful for investigating the structural dynamics of liquid crystals.

We succeeded in detecting heat flux distribution from the microfabricated metal film in microelectromechanical systems (MEMS) by using chiral liquid crystal (Ch) droplets. 10 μm-sized Ch droplets disperse on MEMS devices spontaneously at Ch-isotropic coexisting phase temperature. When we apply electric current to MEMS device, Ch droplets near microfabricated metal film rotate unidirectionally. We estimated local heat flux in MEMS devices by evaluating the rotational behavior of Ch droplets and showed that Ch droplets possess high detection accuracy (0.1 mK/μm).

Nematic liquid crystals (NLCs), with high responsiveness to electric fields and large dielectric anisotropy, are expected to be applied to THz wave devices. However, unlike optical applications, the LC layer thickness for these devices must be several hundred μm or more, which causes a fatal problem of the decay time exceeding several hundreds of seconds. In this study, we attempted to solve this problem using aligned microfiber (MF). Furthermore, we clarified the THz wave characteristics of its complex with LC (MF/LC) and evaluated the variable phase shifter utilizing it as an application example.

In this study, we focused on holmium (Ho), one of the lanthanide elements with excellent magnetic properties, and prepared liquid crystalline metal complexes with Ho as the central metal. The Ho complexes, having a ligand with a β-diketone moiety introduced alkoxy side chain with 8 carbons, were observed to exhibit a cubic liquid crystal phase. Furthermore, the complex exhibits a supramolecular sphere with three molecules arranged in a column, suggesting that it forms a micellar cubic structure. The Ho complexes exhibit excellent magnetic field response to a neodymium magnet and are found to be paramagnetic by SQUID measurement.

Thermotropic ionic liquid crystalline polymers were synthesized by radical polymerization, polycondensation and polymer reaction. Their thermal properties and orientational behavior were examined. The ionic interaction led to the formation of smectic phases with enhanced thermal stability. A side-chain liquid crystal polymer (IP-PE) with an ionic polymer backbone exhibited smectic C and smectic F phases. However, the nonionic family of IP-PE revealed only a nematic phase. Furthermore, in ion-complex type of liquid crystalline polymers composed of polyamine and mesogenic carboxylic acids, the tilted smectic phases such as smectic C and smectic F phases were also formed. The formation of the tilted smectic phases is strongly influenced by the balance between terminal alkyl chain length and ionic interactions.

Short-pitch blue phase liquid crystals appear colorless due to their pseudo-optical isotropy, and detecting their phase transitions can be difficult. Here, we show that a critical transition analysis based on the statistical properties of light scattering signals enables visualization of colorless phase transitions in blue phases. We find that the skewness, or the third statistical moment of the intensity distribution is particularly effective in analyzing phase transitions, since its sign becomes inverted at the transition. The method can be adapted to a wide variety of material systems and microscopy techniques, providing a powerful tool for studying complex critical transition phenomena.

The results of research on liquid crystalline polymers (LCPs) and their related materials are described. Specifically, the behavior of LCPs under electric and magnetic fields, the relationship between the structure and liquid crystalline properties of LCPs, and the development of novel LCPs such as ferroelectric LCPs and ionic LCPs are exhibited. Furthermore, the characteristics of dimeric liquid crystals, polymer-based binary liquid crystals, and polymer-liquid crystal composite films are also revealed.

We fabricate homogeneously aligned reverse mode polymer dispersed liquid crystals(R-PDLCs) using p-type liquid crystal. Isotropic polymers which generate different morphologies, droplet, polymer network and polymer ball types in the normal PDLCs are mixed with an anisotropic polymer (reactive mesogen : RM). A driving voltage decreases by adding the isotropic polymer to the RM. In addition, both high transparency in the off-state and strong light scattering in the on-state can be obtained at a certain concentration of the isotropic polymer.

Toward future optical quantum computing, we have investigated a self-aligned liquid crystal optical control device with 2-slit Young’s experiment. This device can be operated by changing the control of the optical phase of the liquid crystal and we have observed the change in the interference state. To reduce the problem of stray light, the electrode structure was self-aligned, and the alignment of the liquid crystal director was closely changed. As a result, observed voltage change from 0 to 9 V, the “NOT” logic operation was achieved at the sinc function.

In this study, we synthesized diamide derivatives with a biphenyl group possessing two trifluoromethyl (CF3) groups at the molecular center as an electro-responsive moiety, and investigated its liquid crystallinity and ferroelectric properties. The introduction of the two CF3 groups resulted in a columnar liquid crystal phase with a wide temperature range including room temperature, and good polarization switching was observed. In addition, polarization maintenance was also achieved in the temperature range above 90°C, and the ferroelectricity was confirmed to be exhibited.

In liquid crystals, a spatial distribution of the refractive indices can be modulated by controlling the molecular orientation. Thus, liquid crystals have been applied to the various optical materials such as diffraction grating and reflective device. Previously, by the photopolymerization of chiral-liquid-crystalline monomer with intensity-gradient patterned light, we achieved to obtain stripe molecular orientation patterns. The lattice period of stripe pattens didn’t match the helical pitch, indicating the stripe patterns weren’t derived from the helical structure. In this study, we discussed the mechanism of the formation of stripe molecular orientation patterns.

We prepared a chiral azobenzene molecule, which absorbs visible light and undergoes trans-cis isomerization. The change of molecular shape of this azobenzene creates different HTPs. We introduced the chiral azobenzene and a nonphotochromic chiral compound that induces the opposite helical structure into nematic liquid crystals, and fabricated the sunlight-driven smart window that exhibits high transparency in the initial state and shows optical switching to light-scattering state.

Non-mechanical beam steering (NMBS) based on liquid crystals (LCs) is of massive interest in recent years for potential applications such as autonomous vehicles and near-eye displays. To date, most of the studies associated with NMBS based on LCs employ optical phased array (OPA), which utilizes principle of optical diffraction. However, LC-based NMBS have a drawback in that the steering speed is very slow. In this study, we demonstrate refraction-type non-mechanical beam steering with high steering frequency of more than 1 kHz by using a thick LC gel films.

We have successfully visualized the flow using the birefringence of hyperswollen lamellar (HL) phase. We found that the bilayers of the HL phase orient parallel to the flow direction. We have confirmed that the polarized photographs of the HL phases look similar to the corresponding flow velocity fields obtained by the computational fluid dynamics (CFD) simulations. This visualization method enables us to observe the flow continuously and three-dimensionally with our own eyes.

Conventional optical microscopes visualize spatial changes in the refractive index caused by density, concentration, orientation, etc. as a two-dimensional image. In contrast, the fluctuation microscope we are developing is a new microscope that directly visualizes "dynamic inhomogeneity," which indicates spatial changes in the mobility of internal degrees of freedom. In this report, we present the results of measurements of model liquid crystal materials using the fluctuation microscope.

We review our developed PSA (Polymer Sustained Alignment) technology, which realize multi-domain VA (vertical alignment) of Liquid Crystal molecule by both applying fish-bone pixel electrode design and forming the polymer layer in the Liquid Crystal cell using photo-polymerization. PSA technology successfully improved image quality of VA-LCDs and is still widely applied for LCD panels by cost-effective simple processes today.

Transition from a nematic (N) to a smectic (Sm) phase of liquid crystals is called a weak first-order phase transition. In this transition, the generation of pre-transitional fluctuations, which can be measured by X-ray, has been known for long time. The structure of the pre-transitional fluctuation has been considered to be a molecular cluster with Sm-like short-range order, but its role in the transition dynamics and its relation to the weak first-order phase transition have remained elusive. In this study, we observed the structural fluctuation during the N-Sm transition using artificial intelligence and computational chemistry, and discovered the multistep nucleation of Sm nuclei induced by the pre-transitional fluctuation.

Processes of the structural formation in a cylindrical cholesteric droplet with air interface were observed and analyzed. Appling a constant temperature gradient and cooing the droplet from the isotropic state, we obtained the cholesteric droplet via the isotropic-cholesteric coexistence state. After that, by performing specific heating and cooling operations, we obtained the cholesteric droplet with a different structure from that before the operations. It is considered that this structural change is due to the formation and recombination of defect structures during the heating and cooling operations.

In a cylindrical cholesteric droplet with air interface under a temperature gradient, we found that the director field showed a steady rotation, whose direction depended on temperature. The flow-field measurements with the fluorescence photo-bleaching method revealed the appearance of a convection and a rotational flow under the temperature gradient. The rotational flow showed a differential rotation, which is considered to be driven by the convection of an inhomogeneous flow. Moreover, the direction of the convection depended on the temperature as similar to that of the director rotation; it is indicated that the director rotation is also induced by the convection, as well as the rotational flow.

Control of molecular alignment in liquid-crystalline polymer films plays an important role in the development of highly functional materials. A photoalignment method has drawn much attention due to its clean and non-contact process. Recently, we have proposed a novel photoalignment method termed scanning wave photopolymerization (SWaP), where photopolymerization with scanned light triggers molecular diffusion and alignment. In this method, molecular alignment proceeds simultaneously with polymerization and crosslinking reactions; thus, these reactions would affect the alignment behavior. In this study, we investigated the effect of crosslinkers and polymerizable functional groups on the alignment behavior. Furthermore, we evaluated the thermal stability of molecular alignment in the polymer films fabricated by SWaP of monomers with different polymerizable functional groups.

Liquid crystals (LCs) exhibit nonlinear optical effect characteristics based on changes in molecular orientation depending on the incident light intensity. Currently, high light intensity is required to induce nonlinear optical effects, and high light sensitivity of LC materials is strongly desired for device applications. In this study, zinc oxide (ZnO) nanorods grafted with LC polymers were added to dye-doped LCs, and their effect on molecular orientation change upon the irradiation of a light source was investigated. As a result, we succeeded in decreasing the threshold intensity by 39% compared to the case without nanorods.

The numerical simulation of second harmonic generation (SHG) based on the Berreman 4×4 matrix method was performed for a polar helical liquid crystal phase, dubbed helielectric, where the spontaneous polarization rotates helically. We investigated the phase matching conditions for helielectric structures at equilibrium and under electric field. We show the simulation results are consistent with the experiments. The generalized theory enables simulating various SHG properties for arbitrary polar structures.

Berreman’s 4×4 matrix method is a standard method for the analysis of the optical properties of liquid crystals. This method has been widely used to calculate transmission and reflection spectra of liquid crystals. A spatial profile of the electric field in a propagation medium is also important for fundamental research and development of optical devices. We demonstrate the calculation of internal electric fields in liquid crystals by the 4×4 matrix method.

When a voltage is applied to a homeotropically aligned nematic liquid crystal with negative dielectric anisotropy, Schlieren pattern is usually observed. In contrast, when the liquid crystal is doped with ions to increase the electric conductivity and the cell electrodes are covered with insulating films, defects are found to be aligned in a grid pattern. In this study, numerical calculations based on the continuum theory were performed to elucidate the formation mechanism of the grid pattern.