A temperature range of a cholesteric blue phase (BP) was remarkably extended by in-situ polymerization of an appropriate amount of monomers within BP. This material or state with a wide stable BP range has been called "polymer-stabilized blue phase". The stabilizing mechanism is proposed based on thermodynamics and geometrical frustration of orientational order of the composite system. The polymer-stabilized blue phases show anomalously large Kerr effect and fast electro-optic response of less than 1 ms. Therefore, the polymer-stabilized blue phases will contribute toward providing new liquid crystal displays with high quality and low cost, because they are optically isotropic and require no surface alignment treatment.

View full abstract

Customized lyotropic liquid crystal molecules were synthesized for vertical alignment of organic-inorganic hybrid mesostructures. Silica films hybridized with the lyotropic liquid crystals were prepared by hydrothermal deposition method or spin-cast method onto various substrates via sol-gel reaction. The resulting films were characterized by X-ray scattering measurements, atomic force microscopy observations, and transmission electron microscopy observations. As a result, the hybrid films had vertically-aligned mesostructures of the lyotropic liquid crystals to the substrate surface. Furthermore, we achieved preparations of mesoporous silica films with vertical alignment by removal of the lyotropic liquid crystals.

View full abstract

Frustrations in liquid crystalline order create the hierarchical nano structure (space static heterogeneity) or the coupled new hydrodynamic modes of internal degree of freedom (dynamic heterogeneity) due to both static and dynamic couplings between frustrations and liquid crystalline orders.

View full abstract

Liquide crystalline materials are characterized by an anisotropy and dynamics which originate from a spontaneous formation of soft order. A part of their potential characteristics such as optical anisotropy has been so far used mainly in the field of LCD devices and optical components. Here, a diversity of liquid crystalline materials and possibility of their promising application in a variety of fields is discussed.

View full abstract

Pattern formation in liquid crystals is an interesting topicof research. We explore an unconventional schlieren texture of nematic liquid crystals with negative dielectric anisotropy. It is found that the umbilical defects form a square array on a fluorinated polymer surface by applying a moderate electric field. The area of the defects array can be expanded by the self-organization nature or by an optical manipulation technique. We show that the system is highly tunable by several external controls.

View full abstract

Biological applications of liquid-crystalline materials beyond display applications have become much attractive research fields. Recently, we reported that some liquid-crystalline compounds possessing a hydroxyl group show anticancer activity on cancer cell-proliferation. In this study, we prepared some benzoate derivatives and evaluated the anticancer activity on A549 human lung cancer cell-proliferation and the molecular aggregation ability was investigated. As results, 4-butylphenyl 4-(6-hydroxyhexyloxy)benzoate was found to show marked anti-proliferative activity. In addition, the compound have the ability to forms spherical molecular aggregation. We offer a novel approach with liquid- crystalline molecules for anticancer drug design.

View full abstract

In the MC881-MC452 binary mixture system, the near-IR Bragg reflection peak was observed in a wide temperature range from 80℃ down to RT or lower for a narrow concentration region between 54.99 and 57.50 wt.%; the phase responsible for this near-IR Bragg reflection peak was identified as disordered SmC^*-like phase with q_T =1/2, which has the TLAF property in the bulk. We have explained how the TLAF phase is stabilized by four intriguing mechanisms: (1) SRILIs producing the frustration between SmC^* and SmC^*_A; (2) Thermal equilibrium between ferroelectric and antiferroelectric orderings; (3) Emelyanenko-Osipov LRILIs stabilizing the q_T=1/2 state in a wide temperature range; and (4) A ferroelectric hexatic phase emerging on the low temperature side of SmC^*_A.

View full abstract

Systems of hexatic smectic B (HexB) liquid crystal are investigated by constant-pressure and constant-temperature molecular dynamics simulations. By using a symplectic integrator designed for soft matter under a condition where the fluctuation of the system is large, spontaneous transfer among the metastable states is observed. By analyzing the transfer in both directions, distributions of work values corresponding to the forward and reverse processes are obtained.

View full abstract

In the binary mixture system of AS657-MHPOCBC, we have drawn E -T phase diagrams with EFIB (Electric-Field-Induced Birefringence) contours and found several temperature- and electric-field-induced suphases. Some of their approximate at (planar) superlattice structures are successfully determined by using RXRS (Resonant X-Ray Scattering) intensity data. Thus we can appreciate the appropriateness of Emelyanenko-Osipov's LRILIs (Long-Range InterLayer Interactions) to calculate the non-planar structures.

View full abstract

We present a mean field theory to describe a twist-bend nematic phase (N_TB) in the presence of a longitudinal external field parallel to the pitch axis of a cholesteric (Ch) phase. The free energy of the N_TB phase is derived as a function of a usual orientational order parameter of a nematic (N) phase and an order parameter of the N_TB phase. As increasing the strength of the external field, we find that the Ch phase changes to the N phase through the N_TB phase. Our theory demonstrates that the coupling between the director n and the pitch axis p induces the N_TB phase, even if in the absence of the external field.

View full abstract

We performed structural analysis of induced smectic phases, which are composed of polar and non-polar liquid-crystalline molecules. Unlike the conventional understanding that induced smectic phases originate from the formation of charge-transfer (CT) complexes, we revealed that when the CT interaction strength is not so strong, the binary system spontaneously selects the specific integer composition ratio other than 1:1. Our results suggest that the structural formation of induced smectic phases exhibits remarkable similarities to that of metal alloys; that is, the structural stabilization is realized by not only the CT interaction, but also the contributions of molecular-packing effects.

View full abstract

We observed diffraction patterns of smectic E (SmE) phase by using our home-made electron microscope. The advantage of our system is the low-electron beam; this significantly reduces the radiation damage to specimen, and enabled us to observe SmE films without any cryogenic technique. We found in particular that diffraction patterns of SmE phase as an induced smectic phase exhibit unidirectional rotations under electron beams. Since such rotations were not observed in the case of usual SmE phase, we revealed that induced SmE phase possesses well-regulated molecular aliments in the in-plane herringbone lattice, which realizes the spontaneous chiral symmetry breaking.

View full abstract

We prepared an achiral liquid crystal trimer in which two phenylpyrimidine units and a biphenyl unit are connected via flexible heptmethylene spacers, and investigated the phase transition behavior using polarized optical microscopy (POM), differentical scanning calorimetry and X-ray diffraction (XRD). The trimer was found to exhibit a nematic phase and a B4 phase composed of chiral domains with opposite handedness. The chiral characteristics of the B4 phase were confirmed by uncrossing the polarizers in opposite directions. XRD measurements reveal that the B4 phase has a monolayer structure. We discuss how the chirality arises in the B4 phase of the trimer.

View full abstract

We prepared an achiral liquid crystal trimer in which three mesogenic units are connected via flexible spaces. We investigated phase transition behavior of a binary mixture of the trimer and 6OCB using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. A dark conglomerate phase composed of chiral domains with opposite handedness was observed for the binary mixtures containing 55-90 mol% of 6OCB. We discuss how the chirality arises in the binary mixtures.

View full abstract

Triphenylene has been the most representative discotic mesogen. In particular, hexaalkoxytriphenylene has been used for designing many columnar liquid crystalline (LC) materials. Recently, we developed a new triphenylene-based mesogen having six carboxylic ester groups. We found that this mesogen, when modified with paraffinic side chains, can self-assemble to form a hexagonal columnar assembly with an exceptionally wide-range 2D lattice correlation. Furthermore, by virtue of the strong intercolumnar dipole-dipole interaction, the LC triphenylenes spontaneously align homeotropically on a wide variety of solid substrates. More recently, we found that the LC triphenylenes, when bearing certain ionic functionality at the terminal of each paraffinic side chain, assemble into an unprecedented complex three-dimensional architecture.

View full abstract

1,3-Alkadiynyl-4-benzoic acids (mPhDAs) as the rod-like diacetylene compounds exhibited columnar mesophases by hierarchical supramolecular self-organization, while 4-alkoxybenzoic acids (mOBAs) as the saturated carboxylic acids exhibited calamitic mesophases. In this study, we revealed the liquid crystal structures of the mixed system of mPhDA and mOBA and a mechanism for the formation of columnar and calamitic mesophases, which could be converted to each other, depending on their composition and temperature. We directly observed the process of transformation between calamitic and discotic mesophases in order to clarify the mechanism of hierarchical supramolecular liquid crystalline system using the diacetylene carboxylic acid as the building block.

View full abstract

We have demonstrated the formation of segregated nanostructures from disc-shaped electron donor and acceptor molecules through both of covalent and non-covalent approaches. One approach is the use of specific macromolecules where the electron-donating discotic π-systems are arranged one-dimensionally via covalent bonds. The other is the peripheral functionalization of electron-accepting cores by two immiscible side chain pairs that induce the stacking capability in a self-sorting style, when mixed with electron-donating discotic liquid crystalline molecules having conventional alkyl chains. Detailed structural information, thermal property, and electrical conductivity will be discussed in the both two systems.

View full abstract

Herein, we report N-Heteroacene derivatives showing columnar and smectic liquid-crystalline (LC) phases in the wide temperature range including room temperature. Cyclic voltammetry measurements indicate that LC N-Heteroacene derivatives work as electron acceptor and electron donor, respectively. For the electron-accepting LC N-Heteroacene derivatives, these molecules function as electron-transporting properties in the LC thin films.

View full abstract

Photo-alignment of polymerizable liquid crystal (PLC) on poly(methyl mathacrylate) (PMMA)/silsesquioxane containing citraconic imide (SQ-CI) blend was investigated as a model of an unification of two functional layers (photo-alignment layer/planarization layer). In PMMA/SQ-CI blend with γ-butyrolactone as diluent, the PLC was aligned on the blend film after irradiation of linearly polarized UV light to the blend film. On the other hand, the blend with cyclopentanone as diluent showed no orientation of PLC. From the results of photo-alignment and the surface free energy analysis of PMMA/SQ-CI blend, it was suggested that the SQ-CI segregated to the surface of the film despite the higher surface free energy of SQ-CI compared with PMMA.

View full abstract

Dimeric dopants were designed and synthesized for a cooperative effect which originates from two different mesogen units - a cholesterol and an azobenzene moiety connected with a flexible alkylenedioxy bridge. Reversible photoisomerization of azobenzene unit accompanied the unusual switching manner of helical pitch and its helical twisting power (HTP, β), exhibiting larger HTP value in cis-rich state (bent-form). Moreover, based on the large HTP switching upon UV and visible light irradiation (Δβ/β_ini of 50 %), a rotational motion of micro-objects was successfully achieved by the rotational reorganization of the cholesteric helix.

View full abstract

It is well known that N*-LC can be easily prepared by adding a chiral compound into N-LC. In this study, we synthesized various types of axially chiral binaphthyl derivatives bearing the diarylethene moieties and used them as chiral dopants to induce photoresponsive N*-LCs. We investigated the photochemical switching behavior of the N*-LCs through the measurements of polarized optical microscope (POM) and circular dichroism (CD) spectra.

View full abstract

Chiral dopants induce a chiral nematic phase which has a helical molecular arrangement when they are added to a nematic liquid crystal. In this study, we synthesized new chiral dopants having biphenanthrene skeleton and investigated properties of helical twisting power in the nematic phase. As temperature increased, the helical twisting power of (S)-1-OH increased. This feature of helical twisting power has been hardly observed in the case of binaphtyl derivatives. It is suggested that the temperature dependence of helical twisting power of (S)-1-OH was attributed to hydroxyl group. Additionally, the helical sense of chiral nematic phase induced by (S)-1-OEt which adopted cisoid conformation was left-handed. It is found that the chirality transfer mechanism from biphenanthryl-type chiral dopants to host nematic liquid crystals was different from binaphthyl-type chiral dopants.

View full abstract

We report an undiscovered high-speed response component observed in the transient state in cholesteric liquid crystals (ChLCs) with a uniform lying helix. When an electric field is applied normal to the helix axis, two well-known physical phenomena are induced: (i) the flexoelectric effect and (ii) the elongation of the helical structure. In this study, we show that the latter effect can be additionally separated into two different components with fast and slow response times, which reorient the LC director along the electric field without and with the helical pitch elongation, respectively.

View full abstract

We have developed an eye-tracking 3D display using an active barrier which is composed of a new electrode structure. The light leakage between the barrier electrodes has been reduced and the 3D crosstalk has been improved by its electrode structure. Furthermore, a new IPS pixel structure is applied to the LCDs in order to improve the 3D viewing zone.

View full abstract

Electroconvection in nematic liquid crystals was discovered by R. Williams. G. H. Heilmeier invented the first liquid crystal display in the world utilizing a dynamic scattering mode that is a turbulent state of the electroconvection. Though this type of display was not popularly used, the turbulent electroconvection has been researched as a prototype of dissipative structures and turbulence to now. Researches of structures and transport phenomena of turbulence utilizing the nematic electroconvection will be presented in the talk.

View full abstract

The responses of soft-mode turbulence, a kind of spatiotemporal chaos seen in electroconvection of a nematic liquid crystal, to alternating-current (AC) magnetic fields has been investigated to uncover the dynamical properties of spatiotemporal chaos. The dynamical responses can be measured by an order parameter that indicates ordering in the convective roll pattern induced by the magnetic field. Determined by properties of the liquid crystal in a magnetic field, the order parameter oscillated in accordance with the square of the magnetic field. The complex susceptibility obtained from the oscillation shows the Debyetype relaxation spectra in low frequency regime.

View full abstract

Nematic liquid crystals with negative dielectric anisotropy and sufficient ionic conductivity exhibit an electrohydrodynamic convection when ac voltages larger than a threshold voltage are applied. The critical fluctuations inducing the convection has been observed below the threshold by means of shadowgraph technique. Here, we present a new alternative method to visualize the fluctuations through a polarizing microscope by using a chiral dopant, and show that the amplitude and relaxation time increase near the transition point.

View full abstract

In the present work, we compare the switching dynamics of isotropic phase and "foggy" blue phase (BPIII) subjected to an electric field. In order to avoid any side effects from chiral dopants that may occur, a chiral bent-core LC with a spontaneous BPIII is used. The results show that the response time is in the microsecond order in the isotropic phase and increases to 1-2 ms in the BP, then dramatically increases to a few tens of milliseconds when going deeper in the BP. The Kerr constant is also measured and found to be larger compared with our previous work on other bent-core systems.

View full abstract

Phase structures and phase transition behaviors of cubic liquid crystalline compounds, 1,2-bis(4'-n-alkoxybenzoyl)hydrazine (BABH-n, where n is the number of carbon atoms in the alkyl chain) and 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-n), confined in nanoporous glasses having cylindrical pores with different diameters (50, 100, 200, and 500 nm) were studied using DSC and synchrotron-radiated XRD. When the pore diameter was decreased, interestingly, melting point and clearing point reduced whereas the phase transition temperature from Im3m- to Ia3d-Cubic phases increased. We considered this is due to restricted thermal expansion of the liquid crystalline compounds in the nanopores.

View full abstract

1,2-bis(4π-n-alkoxybenzoyl)hydrazine (BABH-n, n is the number of carbon atoms in the alkyl chain) is one of typical bicontinuous cubic (Cub_<bi>) liquid crystalline compounds. The Cub_<bi> phase has three-dimensionally periodic structure. Starting from the BABH-n, we have successfully synthesized eight compounds by extending π-conjugated system in the core part (i.e., benzene ring to biphenyl, stilbene, phenylacetylenephenyl, and naphthyl rings). Irrespective of usual high sensitivity to the chemical structure of the phase formation, very surprisingly, all compounds were found to exhibit the Cub_<bi> phases. In this presentation, we examine the relationship between the size of the core part and the phase transition behavior of the Cub_<bi> phases.

View full abstract

Recently, we achieved the UV-induced liquid crystalline phase transition from 1D-organized smectic C (SmC) to the 3D-organized bicontinuous cubic (Cub_<bi>) phase utilizing the photoisomerization of an azobenzene derivative. The sample is a binary mixture containing 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-22) and azobenzene derivative 4-(4'-n-docosyloxyphenyl-azo)benzoic acid ethyl ester (azo-COOEt-22). In this work, we investigated effects of the concentration of azo-COOEt-22 and temperature on the phase transition rate using time-resolved measurements of grazing-incidence X-ray diffraction (GI-XRD) and birefringence.

View full abstract

We propose a simple Ginzburg-Landau model for phase transition dynamics in liquid crystals. This model is capable to reproduce phase transitions among isotropic, nematic, smectic A and smectic C phases with controlling only a few parameters. On the basis of this model, we also demonstrate numerical simulations. We observed that a polydomain pattern is formed in an early stage of isotropic-smectic A transition and its characteristic length grows in time as l ∝ t^0.25, for example. On the other hand, phase transition into smectic C shows a zigzag pattern, which coarsens in time more slowly.

View full abstract

We fabricated the nematic (N)- and the smectic A (SmA)- liquid-crystalline nano-emulsions (LCNEs), and measured the time evolution of the layer structure of the mixture of the N- and SmA-LCNEs by the time-resolved synchrotron X-ray diffraction experiment. Then, it was revealed that the layer spacing and the correlation length continuously decrease, which reflects the progress of the diffusion of the liquid crystalline molecules. Based on the time evolution of the layer spacing, we discussed the mobility of liquid crystalline molecules in the core parts of the micelles..

View full abstract

Aiming at a pseudo-biomembrane, as the first step, we made phospholipid films in which the LC domains with several 〜 several-tens of micrometer diameter were well dispersed, both at the air-water and oil-water interfaces. The heterogeneous lipid films were then transferred from the oil-water interface to the vesicles by means of inverted emulsion method. The giant unilamellar vesicles were successfully made, but so far we could hardly find the embedded LC domains. The process should be improved such that the film structure at the interface is not broken.

View full abstract

I analyzed the local nano-structure in the binary mixture of a bent-shaped liquid crystal and a rod-like cholestreric mixture using small-angle X-ray microbeam scattering. It was found that three types of nano-scale phase-separated structure occur, depending on the cooling process, and in particular, two of them simultaneously appear in the gradual cooling process (less than -0.1℃/min.). Moreover it was also found that a liquid crystalline order, which is different from that in the original molecules, occurs in this system, which is assumed to be induced by the B4 helical filament working as a biasing field.

View full abstract

The numerical experiments and computer simulations predicted the entropy driven assembly of spheres segregated into the interstitial regions between the smectic layers of rods in a rod-sphere mixture due to the depletion effect. In this study, the smectic liquid crystal supramolecular assembly in the mixtures of a sphere-like particles and rod-like polysilanes with narrow molecular weight distributions were investigated by synchrotron radiation small-angle and wide-angle X-ray scattering measurements (SR-SAXS/WAXS) and atomic force microscopy (AFM) observations and found to reproduce the theoretical predictions accurately.

View full abstract

Recently, LC display with a fringe-field switching mode (FFS-LCD) has been applied to high definition TVs, smartphones, and so on. However the transmittance of FFS-LCD is not enough high to achieve further requirements for high definition. To achieve enhancement of the transmittance, we have designed and synthesized novel LC compounds with positive Δε having a -CF₂O- linkage and a 2, 3-difluorophenylene moiety. These compounds have a quite larger value of ε⊥ in comparison with conventional positive LC compounds. Mixtures including these compounds successfully achieve higher transmittance, quicker response and higher reliability of displays, simultaneously.

View full abstract

Nano-Phase Separated Liquid Crystals(NPS-LCs) with fast response time have been investigated. NPS-LCs are prepared by forming polymer network in liquid crystal host by photo-induced phase separation process with photo-curable monomer. NPS-LCs achieve 40% faster decay time compared to Polymer Sustained Alignment Liquid Crystals(PSA-LCs). The faster decay time which is attributable to strong interaction between the polymer network and the liquid crystal host, is maintained even at low temperature.

View full abstract

We investigated photoinduced plasticization of polymer composites containing azobenzene derivatives and nematic liquid crystals (LCs). At the initial state, a composite had a structure in which an azo-containing LC formed small domains by a phase separation from a polymer matrix and the whole composite showed glassy state and a high storage modulus over 10⁷ Pa at room temperature. On irradiation of the composite with ultra-violet light which induces trans-cis photoisomerization of an azobenzene derivative, we observed the photochemical nematic-to-isotropic phase transition of the azo-containing LC domains. At the same time, the storage modulus and the glass transition temperature of the composites were reduced (photoinduced plasticization). In a composite with an appropriate composition, we successfully achieved glass-rubber transition by means of the photoinduced plasticization based on the photochemical phase transition of an azo-containing LC. The photoinduced plasticization of the composites would be attributed to the differences in the plasticization abilities of nematic and photochemically-induced isotropic phases of an azo-containing LC. By using the photoinduced softening of the azobenzene-functionalized composites, we have developed photoresponsive adhesives and self-healing materials.

View full abstract

In order to improve the mechanical and self-healing properties of particle/liquid-crystal (LC) composites, we incorporated polymer chains into the composites by using polymer-brush-afforded silica particles (P-SiPs) as a particle component. The composites consisting of P-SiPs and a nematic liquid crystal (5CB) showed high strength and shape recoverability due to the elasticity derived from rubbery polymer chains. A small dent made on the composite surface could be spontaneously repaired at room temperature. Moreover the composites consisting of P-SiPs and photoresponsive 5CB (P-5CB) where 5CB contains a small amount of an azobenzene derivative, exhibited gel-sol transition by the photochemical phase transition of P-5CB. Using the photoinduced gel-sol transition, we achieved the light-mediated mending of a surface crack as well as the spontaneous repairing of a surface dent on the composite gels.

View full abstract

Novel main-chain liquid crystal polyurethanes were synthesized by the polyaddition of diols and diisocyanates. Their metal-complexed family was also obtained by the reaction of the polyurethanes and metal ions. The polyurethane/metal complexes exhibited nematic or smectic A phases, characterized by the X-ray diffraction pattern consisting of the inner sharp reflections and the outer broad reflection. The liquidcrystalline polyurethane/copper(II) complex revealed a higher order parameter (0.67) when compared to the liquid-crystalline polyurethane (order parameter=0.5). The copolyurethane/copper(II) complexes obtained from nonmesomorphic copolyurethanes formed a metal ion-dispered nematic phase with a schlieren texture.

View full abstract

Fluorine-containing gold complexes would be promising materials due to a strong luminescent property through Au-Au interaction and an aggregation property between fluoroalkyl chains through fluorophilic interaction. Recently, we have developed a series of rod-shaped gold complexes having fluoroalkyl group into the mesogenic aromatic ring, one of which was found to emit a strong blue photoluminescence in the solid states. We describe, herein, new feature of the fluorine-containing gold complexes, which found to exhibit liquid-crystalline behavior. We discuss on the liquid-crystalline and photoluminescence behavior of such gold complexes, and the relationship between their properties and aggregation structures.

View full abstract

Collagen is a useful protein with a strong mechanical property and high biocompatibility, and collagen has been used as biocompatible soft materials for medical applications. To fabricate such materials, control of molecular alignment plays an important role. Various molecular alignment methods have been explored; however, the existing methods have drawbacks in complicated manufacture processes and costly equipment. In this study, we aimed to fabricate a large-area oriented collagen film by means of surface relief template.

View full abstract

Lemke dye is one of the nonlinear optical (NLO) materials. This has a pentaene moiety, bearing dicyanoethylene and amino groups, viz. a push- and pull-structure. In previous studies, generation of THz wave was achieved from poled polymer films containing Lemke dyes. In general, organic NLO materials based on Lemke dyes are crystalline. Liquid crystal (LC) phases have dynamic ordered structures. This feature is favorable for the production of thin films by a wet process and control of molecular orientation by external stimulus. In this study, we report Lemke dye derivatives bearing oligosiloxane chains and production of thin films by a spin-coating method.

View full abstract

We have proposed a hybrid alignment nematic liquid crystal cell using a polymer stabilized technology. In a polymerization process, a UV penetration depth is carefully considered, which results in a change of polymer morphology. The UV irradiation from a homogeneous alignment substrate side causes a polymer rich layer near the substrate and the stronger scattering in the on-state.

View full abstract

Triplet-triplet annihilation-based photon upconversion (TTA-UC) has been recently demonstrated in the columnar liquid crystals (LCs) containing π-stacked perylene arrays. In order to understand the mechanism of triplet energy migration in the columnar LC system, we analyzed the microscopic structure in detail by means of molecular dynamics simulations. As a result, we confirmed that the structural order played the essential role in the triplet energy migration and co-assembly of perylene derivatives possessing different alkyl chains increased both the structural order and the energy migration.

View full abstract