Topological defects in nematic liquid crystals are interesting for optical applications. Here we study the Talbot self-healing effect obtained from a regular array of umbilical defects which is self-organized by an electric field. By adjusting the distance from the sample cell, we observe that a uniform pattern can be reconstructed at the Talbot plane. In this presentation, we study the propagation of light and the quality of beams.

The cubic (Cub) phase is a liquid crystal phase with a three-dimensional network, and its formation depends on the chemical structure of the molecules. Of 1,2-bis(aryloyl)hydrazine-based molecules, elongation of the π-conjugated system (from benzene to biphenyl, for example) extends the temperature range of the Cub phases. In this study, we focus attention on the effect of the side group introduced into the molecular core on the phase transition behavior and reveal that in addition to the steric effect, an electron-withdrawing nature of the fluorine atom plays an important role in the phase formation.

Pattern alignment technology for liquid crystal devices has made it possible to control the molecular orientation of liquid crystals, enabling the generation of complex liquid crystal structures such as topological defects. Topological defects in liquid crystals exhibit properties different from those of uniformly oriented liquid crystals. In this study, we used Landau-de Gennes theory to calculate the molecular orientation of pattern-aligned nematic liquid crystals with defects. The optical properties of the pattern-aligned nematic liquid crystal in a dielectric multilayer coated cell were analyzed using the FDTD method.

Cholesteric blue phases (BPs) have attracted significant attention from both fundamental and practical perspectives. In recent years, controlling the lattice orientation of BPs has been investigated to improve device performance. Although alignment layers play an important role in the liquid crystal orientation, little is known about the influence of alignment layers on the lattice orientation of BPs. In this study, we found that the tilt of the BPII lattice orientation with respect to the orientational easy axis is induced by the chirality of the BPLC. We also found that the lattice orientation changes drastically just below the Iso-BPⅡ phase transition temperature.

We synthesized bisureas 1 to 3 to investigate the effect of the alkyl linker length linked the two urea groups in the molecule on the liquid crystal property and electro-responsiveness. Compound 3 has a liquid crystal phase with an ordered structure at room temperature and an assembled state with long-range order at high temperature. SHG measurements revealed that compound 2 partially relaxed its polarization at 70°C after removal of the applied electric field, while compound 3 showed complete polarization maintenance after the removal.

Liquid crystal (LC) lenses with a circular electrode and ring electrodes was proposed and their lens properties of Fresnel lens type refractive index have been realized by adjusting the applied voltages across the patterned electrodes and the common electrode. In this study, we calculate three-dimensional LC molecular orientations for an LC lens with a highly-resistive layer coated on the ring electrodes, and tilt and azimuthal angle distributions in the lens area can be obtained. The optical phase difference and lens power can also be calculated.

The novel orientation behavior was observed so that the pretilt angle of nematic liquid crystals on vertical alignment polyimide films irradiated-ultra-violet (UV) continuously varies from vertical to horizontal alignment as a function of dose amounts. This study investigated the phase transition behavior from the nematic phase to the isotropic phase to understand the liquid crystal orientation phenomenon in which pretilt angle changes upon UV-irradiation for the polyimide film. We observed that the phase retardation changes rapidly under the vicinity of the phase transition temperature. This result indicated that the liquid crystal orientation order decreased at the surface interface prior to that in bulk.

Nonlinear optical materials whose optical properties change in accordance with an incident light intensity have attracted much attention. In particular, liquid crystals (LCs) can reversibly control their molecular orientation based on nonlinear optical effects. The doping of oligothiophene dye into LCs increases the light sensitivity. Further enhancement of the light sensitivity is still desired for practical applications. In this study, we investigated the effect of the host LC structure such as fluorinated LCs on the nonlinear molecular reorientation behavior, aiming to increase the sensitivity of the photoinduced molecular reorientation.

RTN liquid crystals can be driven at low voltages by introducing torsion into the liquid crystal material. RTN require polymer stabilization because they become splay-twisted when no electric field is applied. Since an electric field must be applied during polymer stabilization, transmittance becomes low when no voltage is applied. For this reason, we aimed to improve transmittance by using a dual-frequency driven liquid crystal. We verified whether the RTN structure can be stabilized by applying high frequency and making the Δε of the liquid crystal material negative. The structure and characteristics of the liquid crystal stabilized by the application of high frequency are reported.

We synthesized a liquid crystalline perylene bisimide derivative bearing a triethylene oxide chain and the cyclotetrasiloxane rings. This compound was hybridized with lithium triflate and the mixture exhibited a columnar hexagonal phase. From thermal analysis, lithium triflate should be dispersed homogeneously although segregation of lithium triflate in a thin film state from an AFM observation. A dielectric study indicated a relaxation process originated from motion of lithium ions between triethylene oxide chains.

A planar oriented side-chain liquid crystal (SCLC) random copolymer with azobenzene and cyanobiphenyl side chains was designed. The SCLC block copolymers were synthesized with a caged silsesquioxane (POSS) poly methacrylate at lamellar and cylinder morphologies. The thin films of the block copolymers were prepared and annealed above the isotropic temperature. When the block copolymer thin films were irradiated with linearly polarized light (LPL) at 430 nm, large dichroism was observed at absorption bands due to the mesogenic side-chains. The optical order parameter with cylinder structure was higher than that with lamellar structure. The thin films without annealing process were also irradiated with LPL in the same way. The dichroism was greater than that of the annealed one.

We have reported that CnDIO (n=1,2,3,4), a liquid crystal compound having a 1,3-dioxane skeleton, exhibits a ferroelectric nematic phase (NF phase) with a huge relative permittivity of over 10,000. However, the temperature range in which CnDIOs exhibit the NF phase is higher than room temperature, and it is desirable to expand the temperature range of the NF phase to lower temperatures. In this study, we systematically mixed various CnDIOs to lower the freezing point based on mixing-induced melting point depression, and succeeded in extending the temperature range of the NF phase to the lower temperature side.

Crosslinked liquid-crystalline polymers containing azobenzene moieties can be reversibly deformed by light irradiation. However, previous photomobile materials were powered only by UV light, and it was difficult to use sunlight mainly composed of visible and near-infrared light. In this study, we fabricated sunlight-driven photomobile materials with push-pull azobenzene, which contain both an electron donor and an acceptor at both ends of the azobenzene moiety. The resulting films bent toward a light source when irradiated with sunlight and the bent films reverted to their initial states under dark. This result indicates that they showed reversible deformation in response to sunlight.

The isotropic-nematic phase transition is generally a first-order phase transition. It is theoretically predicted that a triple critical point will appear when an electric field is applied to a nematic liquid crystal with a negative dielectric anisotropy. We have shown that soft mode can be observed by performing dielectric measurements under a DC electric field. Therefore, in this study, we attempted to measure the soft mode from the permittivity measurement using the method proposed in the previous research. As a result, it was clarified that when an electric field of a certain magnitude or more is applied, a peak due to the soft mode appears in the temperature dependence of the permittivity.

We investigate the dynamic viscoelasticity of liquid crystal elastomers under various degrees of tensile static strain. The damping (loss tangent) considerably increases with increasing the imposed static strain in the strain regime below the onset of the director rotation in isotropic-genesis polydomain nematic elastomers.

Liquid crystalline elastomers (LCEs) containing photothermal conversion materials are expected to be applied to soft actuators. From our previous studies, we have prepared a LCE containing photothermal conversion materials and found that the LCE bends toward the photothermal conversion layer with laser irradiation. In this study, we prepared a LCE coated with two types of polymer films with different absorption wavelengths, and made it possible to control the bending direction by the wavelength of the irradiation light source.

Ferroelectric columnar liquid crystals (FCLCs) are promising materials for sensors and memory. In our laboratory, FCLC was reported to appear in diphenylurea molecules with chiral side chains, but the details of the mechanism remained unclear. In this study, we prepared four molecules in which each of the chiral chains at the phenyl group was regioselectively introduced, and investigated the correlation between the ferroelectricity and the arrangement of chiral groups. As a result, it was found that the arrangement of the chiral chains causes differences in the formation of helical columnar structures, which affects the ferroelectricity.

In recent years, liquid crystal (LC) optical elements such as LC lens and grating have shown remarkable development, owning to advances in photoalignment technologies. Various techniques have been reported to spatially control LC orientation in the azimuthal direction. However, there were few reports that LC orientation was spatially controlled in the polar direction. This study shows that LC pretilt angle is spatially controlled with ultra-violet (UV)-irradiation to the vertical alignment polyimide film, and the grating structure was fabricated using this alignment technique

Inorganic nanomaterials such as nanorods and nanotubes have been thrust into the limelight due to their various anisotropic properties. The alignment control of the anisotropic nanomaterials is key to the development of functional materials. We have recently proposed a simple method for the unidirectional alignment of ZnO nanorods on an alignment layer. In this method, ZnO nanorods are grafted with liquid-crystalline (LC) polymers and are aligned cooperatively with surrounding host nematic LC molecules. The increase in the fraction of nanorods in the system and the elongation of nanorod shapes are desired to fully utilize their anisotropic properties. In this study, we synthesized LC polymer-grafted ZnO nanorods with different aspect ratios and investigated their alignment behavior.

We have reported a composite of liquid crystals and porous crystals of metal-organic frameworks (MOFs), which exhibits a birefringence with high temperature-responsivity derived from the orientation of liquid crystals inside the pores of MOFs. In this study, we focused on the crystal system of MOF and investigated the influence on the optical properties of the liquid crystal/MOF composites. The liquid crystal/MOF composites were prepared by using MOFs with cubic, triclinic, hexagonal, and orthorhombic crystal systems, and the birefringence and the orientation of the liquid crystal were evaluated.

Two homologous series of ester-linked cyanobiphenyl dimers (CBCOOnOCOCB) and fluorinated homologs [(2-F)CBCOOnOCOCB)] were synthesized and their phase-transition behavior was evaluated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Upon cooling of POM for CBCOOnOCOCB, a nematic (N) phase was observed in the supercooled isotropic (Iso) phase for all n, and the N phase of n = 7, 9, 11 transitioned to a twisted bend nematic (NTB) phase. No liquid crystal phase was observed for (2-F)CBCOOnOCOCB (n = 3 and 5), whereas (2-F)CBCOOnOCOCB (n = 9 and 11) exhibited both the N and NTB phases. Interestingly, (2-F)CBCOO7OCOCB formed the NTB phase from the Iso phase.

We have already developed oligo(p-phenylenevinylene) derivatives exhibiting a cholesteric phase at room temperature. Hole transport and circularly polarized luminescence have been observed in the cholesteric phase of these compounds. For stable cholesteric phase in low temperature region, we synthesized oligo(p-phenylenevinylene) derivatives bearing longer alkyl chains at lateral positions. The cholesteric liquid crystal bearing lateral propoxy groups exhibited an enantiotropic cholesteric phase.

It is important to investigate electromagnetic wave transmittance characteristics to attain large-scale LC devices with high transmittance that can be used as smart windows. So far, it was found that the millimeter-wave transmittance can be increased by introducing a grid electrode structure. However, the decrease in the driving area is a problem. In this study, we investigated the relationship between the grid period and millimeter-wave transmittance to optimize the grid electrode design.

In our previous work, it was found that some liquid crystalline compounds containing coumarin skeleton at a terminal position gelated various organic solvents when the compounds heated and dissolved in solvents then cooled. While molecular arrangements when the compounds behave as liquid crystalline compound and gelators were not elucidated. In this work, cinnamate (compounds 1-n) and biphenyl derivatives (compounds 2-n) having coumarin skeleton were synthesized and examined liquid crystallinity and gelation ability in several organic solvents. Compounds 1-n were not able to gelate, however compounds 2-n were able to gelate 1-octanol, dimethyl sulfoxide and propylene carbonate. In addition, these compounds were exhibited smectic A phase and/or nematic phase.

A device that makes a difference in transmittance depending on whether the directions of incident angles was developed using hybrid alignment nematic (HAN) liquid crystal (LC), polymer dispersed LC, or guest-host (GH) HAN LC. The same properties have also been obtained by electrically controlled birefringence(ECB) devices with high pretilt angles. For the pretilt angles to be sustained high, there is a method of a mixture of horizontal polyimide and vertical polyimide. In this study, the various pretilt angles were stabilized under the various condition, such as, rubbing strength, baking temperature, and concentration of polyimide.

Recently, our research group reported photoresponsive side-chain liquid crystalline (SCLC) random copolymers with azobenzene (Az) and cyanobiphenyl (CB) side-chains adopted the random planar orientation with relatively high liquid crystalline (LC) temperature. In this research, we synthesized block copolymers composed of the photoresponsive random copolymer block with a high glass transition temperature, such as polystyrene and poly(4-vinyl pyridine). The synthesized random copolymers exhibited a wide range of LC temperatures in high regions and isotropic temperatures 10-35℃ higher than each homopolymer. The block copolymers with the random copolymers showed the same LC temperature. In-plane photoalignment of the random copolymer and block copolymer films was performed by irradiation of linear polarized light at 365 nm or 436 nm.

In the past few years, there have been a series of reports on nematic liquid crystals (LCs) exhibiting large dielectric permittivity exceeding 10,000 and having ferroelectricity. However, its mechanism and the detailed structure and dynamics of ferroelectric LCs have not been clarified thus far. In order to gain new insights for understanding the polar structure of the molecular assembly, we investigated the change of the orientation structure and diffusion behavior of ferroelectric nematic LCs by using molecular dynamics simulations.

In this research, the synthesized perovskite nanosheet colloid with structural color was immobilized into polymer hydrogel by in-situ photo-initiated polymerization to develop a novel mechanochromic material. The parallel structure of nanosheet inner the gel was confirmed by UV-Vis reflective spectrum, small angle X-ray scattering. The structural color of the hydrogel is adjustable in full-color range. The hydrogel exhibits a reversible mechanochromic property of responding to weak mechanical stimuli less than 1 kPa within 1 ms. These excellent properties can be applied to mechano sensors and displays.

Nematic liquid crystals with positive dielectric anisotropy exhibit a critical endpointunder the electric field, and isotropic-nematic phase transition disappears above a criticalendpoint. In this study, we investigated the dielectric dispersion in the nematic liquid crystal withpositive dielectric anisotropy, 8CB, near the critical endpoint under several conditions of temperatureand electric biasing field. As a result, the critical slowing down was found. The behavior of therelaxation frequency of the soft mode was clarified.

We doped bridged azobenzene (B-Azo) into chiral nematic liquid crystals (LCs) as a photoresponsive molecule. When the mixture was exposed to visible light, B-Azo exhibited photoisomerization behavior in LCs, which was accompanied by an isotropic to nematic phase transition of the mixture. In addition, we prepared a smart window composed of host LCs and B-Azo. Transmittance of the smart window decreased upon exposure to visible light, and the smart window reverted to the transparent initial state in the dark. This result indicates that the change in transmittance is attributed to photochemical phase transition triggered by photoisomerization of B-Azo.

We have developed a two-step polymerization method using hetero-bifunctional crosslinkers to introduce crosslinking structures into the liquid crystal polymeric particles with unique molecular orientation. To obtain the particles with high solvent and thermal resistance, high crosslinking density is desired. In the present study, we synthesized microparticles with both high crosslink density and the molecular orientation by using hetero-functional crosslinkers exhibiting liquid crystalline phase. We also discuss the molecular orientation control in the obtained microparticles.

Previously, we found that adding colloidal particles to a lamellar phase of surfactant in water inhibited collisions between adjacent lamellae, reducing the layer compression modulus. Here, we assess whether mixtures of colloids and a sponge phase reflect similar phenomenology. Dynamic light scattering (DLS) experiments at low surfactant concentrations showed a two-step relaxation and dispersion consistent with superimposed colloidal dynamics (fast) and topological fluctuations in the sponge phase (slow); however, at concentrations where the interlayer separation approaches the particle size, the slow relaxation was made drastically slower, accompanied by a similar slowdown in the colloid-associated fast relaxation. This may evidence a dynamical coupling between particle diffusion and topological fluctuations at higher surfactant concentrations.

We have focused on holmium (Ho), one of the lanthanide elements with excellent magnetic properties, and have been developing soft materials containing Ho. Since lanthanides have different luminescence and magnetic properties depending on the element, we have prepared liquid crystalline complexes with various lanthanides as the central metal in this study. Lanthanide complexes with 12-carbon alkoxy chains as a side chain formed columnar liquid crystals, which showed different properties depending on the type of central metal. The columnar liquid crystals composed of these lanthanide complexes were analyzed in detail and their physical properties were investigated.

Block copolymers spontaneously form nanoscale periodic structures through microphase separation. Precise alignment control of nanostructures plays an important role to achieve anisotropic functional materials. Recently, we have reported the unidirectional alignment of microphase-separated structures of liquid-crystalline (LC) block copolymers on an alignment layer. Besides, we have proposed a simple and powerful method for controlling molecular alignment of LC polymers termed scanning wave photopolymerization. Photopolymerization in a selected area induces molecular diffusion leading to the uniform alignment of anisotropic molecules along the diffusion direction. In this study, we synthesized LC block copolymers by scanning wave photopolymerization, and investigated formation behavior of the microphase-separated structures.

We synthesized liquid crystalline perylene bisimide derivatives bearing an ion-transporting imidazolium moiety and polymerizable cyclotetrasiloxane rings. These compounds exhibited columnar phases in which electron-conductive π-stacks and ion-transporting channels were integrated on nanometer scales. The structures of the columnar phases were affected by counter anions. The electrochromic behaviors of the polymerized films of these compounds depended upon the size of counter anions. This result indicated a potential for ion-size recognition in the liquid crystalline thin film.

We have synthesized two homologous series of thioether- and ester-linked 4-cyanoazobenzene- and 4-cyanobiphenyl-based dimers (CBCOOnSAzoCN and CBOCOnSAzoCN) with different numbers of the carbon atom in the methylene spacer (n = 2, 4, 6, 8, 10). We found that all the dimers except CBOCO2SAzoCN exhibit a twist-bend nematic phase as well as a conventional nematic phase upon cooling. Both CBCOOnSAzoCN and CBOCOnSAzoCN homologs showed higher phase-transition temperatures than 4-cyanobiphenyl-based dimer counterparts, whereas no significant difference in their associated entropy changes were observed. Light-induced phase transition was also examined for both the homologs with n = 6.

We have investigated a 90° TN reverse mode PDLC (R-PDLC) cell which has a transparent off-state and light scattering on-state. This mode has the advantage of light scattering both ordinary and extraordinary ray. In this study, we have investigated forward light scattered patterns of the ordinary and extraordinary ray under the voltage application. The light propagating the cell is diffused and spreads perpendicular the polarization direction of the light and the scattering mechanism in the 90° TN R-PDLC is discussed through the scattered patterns.

We synthesized a block copolymer with azobenzene (Az) side-chain liquid crystal (LC) polymer block (POAz) and polyethylene oxide methyl ether methacrylate (MEO) polymer block (PMEO-b-POAz) with microphase PMEO cylinder morphology by reversible addition fragmentation chain transfer (RAFT) polymerization. Comparison of UV spectra in thin films under heating and after annealing was performed to estimate the molecular orientation of LC Az side-chains. At film thicknesses above 100 nm, the absorption bands due to π-π* transition of Az were significantly decreased after annealing. On the other hand, for thin films of less than 50 nm, the absorption band was almost unchanged in the annealed films. These results indicate that the LC orientation and PMEO microphase cylinders depend on the film thickness.

THz wave is waves located between light and radio waves, and is expected to be used for next next-generation wireless communication and nondestructive testing. In order to realize these applications, tunable THz elements are requisite. Liquid crystal device is one of the strong candidates for high performance THz elements because of its controllability with low drive voltage and low power consumption. Recently we have reported that hydrogen-bonded liquid crystals do not exhibit absorption anisotropy in the THz band. However, there are few reports on the temperature dependence of the properties of liquid crystals in the THz band. In this study, we show that the temperature dependence of the complex refractive index in the THz band.

In our previous work, it was found that some liquid crystalline compounds having coumarin skeleton at a terminal position gelated various organic solvents. The organo-gels formed by them were physical gels, so their sol-gel transition was occurred by heating and cooling. In this work, 2-oxy-2H-chromen-6-yl 4-alkoxybenzotates were synthesized and examined liquid crystallinities and gelation abilities in several organic solvents. As the results of them, some synthesized compounds exhibited nematic or smectic A phases by monotropic transition, and it added in amount of 5wt% or less were able to gelate poly(ethylene glycol)-400 (PEG-400).

The behavior of liquid crystal (LC) molecules at the LC/substrate interface plays an important role in their application. we have been studying the viscoelasticity of liquid crystal molecules near the interface using the quartz crystal microbalance (QCM). Recently, we have investigated the viscoelastic changes at the interface during the formation process of LC thin films by in-situ viscoelastic analysis using the QCM during vacuum deposition of LC. In this study, we investigated the deposition rate dependence of the viscoelastic evolution in LC thin films.

Molecules in nano-pore show different properties from those in the bulk. We focused on metal-organic frameworks (MOFs) with high surface area and high designability as a flask of liquid crystal (LC). In this study, MOFs with different substitution positions and substituent groups were adopted to obtain LC/MOFs composites. The LC/MOFs composites substituted with the 2-position on the 4,4’-biphenyldicarboxylic acid (bpdc) type ligand showed thermo-responsivity in retardation, whereas LC/MOFs composites substituted with the 3 or 5-position did not show thermo-responsivity in retardation, indicating that the substituent position of bpdc-type ligand determine the thermo-responsivity of optical anisotropy in LC/MOFs.