Axially polar ferroelectric columnar liquid crystals have been expected to be applied to some novel devices, such as ultrahigh density memory and nano-patterning substrate. However, since the liquid crystal remains in a fluid state, external physical pressure and static electricity would cause damage to the recording structure. In this study, to solve such problems, we designed a new compound possessing urea moiety, two biphenyl moieties, and four branched side chains, which had "similar packing structures" before and after its liquid crystal-to-crystal phase transition occurring at around room temperature. This phase transition mechanism enables long-term storage utilizing crystalline transition without damaging the polarization information recorded in the liquid crystal phase.

Liquid crystalline dimers consisting of two cholesteryl moieties linked with nitrophenylene and phenylene were synthesized. The dimer compounds exhibited a chiral nematic liquid crystal phase, and its reflected light shifted over a wide wavelength range from red to blue in response to slight temperature changes. When these liquid crystal dimer compounds were added to a rod-shaped liquid crystal compound as chiral dopants and a vertical voltage was applied in an ITO cell, the color tone shifted from red to blue at low temperatures. The phase transition behavior, liquid crystallinity, and color change behavior were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), one-dimensional X-ray diffraction (1D-XRD), and microscopic reflectance spectroscopy.

A lot of functional cyclotriphosphazenes have been prepared, and their physical properties were investigated. It is also known that fluorination has effect on the thermal property and molecular arrangements of liquid crystal compounds. On the other hand, several kinds of perfluoroalkylated compounds can gelatinize various organic solvents. In this work, cyclotriphosphazenes with a perfluoroalkylethylthiophenyl group (compounds 1-n and 2-n) were prepared as shown Figure 1, and their liquid crystal property and gelation ability were studied by differential scanning calorimetry (DSC) measurements, polarizing microscope observation, and binary phase diagrams.

Liquid crystalline elastomers (LCEs) have both responsivity for the external stimulus responsiveness of LC and flexibility of polymer chains. Therefore, LCEs are expected as soft actuators. By incorporating photothermal conversion materials such as gold-coated fine particles, the macro shape of LCE can be controlled by light irradiation. In this study, LCE coated with two types of polymer films with different dyes and made it possible to control the bending direction by the selection of near-infrared and visible light sources.

Liquid crystalline block copolymers, P5OAz-b-PPOSS, with azobenzene (Az) and polyhedral oligomeric silsesquioxane (POSS) derivatives were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. P5OAz-b-PPOSS thin films with Az cylinders in perpendicular direction to substrates were induced by nonpolarized visible light (430 nm) irradiation at 50 °C for 40 min. Porous silica thin films were prepared by oxygen plasma etching for direct decomposition of Az cylinders and oxidation of POSS moieties. Porous nanostructures and ion permeability of the silica thin films were investigated by atomic force microscopy (AFM) and cyclic voltammetry (CV) measurements, respectively.

Anisotropic inorganic nanomaterials have gathered much attention due to their unique shape-dependent properties. The alignment control of the anisotropic nanomaterials is important for the development of functional materials. We have recently proposed a simple method using an alignment layer for the unidirectional alignment of ZnO nanorods surface-modified with liquid-crystalline (LC) polymers. In this method, the polymer-grafted ZnO nanorods are cooperatively aligned with host nematic LCs on the alignment layer. The increase in the fraction of nanorods is desired to utilize their anisotropic properties effectively. In this study, we synthesized LC polymer-grafted ZnO nanorods and investigated their alignment behavior.

Block copolymers consisting of hydrophilic and hydrophobic blocks show microphase-separated structures and have recently drawn considerable attention as nanoscale permeable membranes for industrial and agricultural applications. In this study, we synthesized block copolymers comprising hydrophobic photoresponsive polyurethane and hydrophilic polymer. We attempted to create materials in which the permeability can be controlled by light irradiation.

Microcapsules have attracted attention as micro-sized containers for drug delivery systems and microreactors. Liquid crystalline (LC) microcapsules, whose shells consist of liquid crystalline materials, show unique functions that take advantage of their high responsivity to stimuli. Further miniaturization of microcapsules can expand the range of applications. In this presentation, we report on a method to fabricate small LC microcapsules using porous membranes.

Polymeric liquid crystals (LCP) containing N-benzylideneaniline (NBA) can be photo-aligned by linearly polarized light irradiation and subsequent annealing. The oriented NBA mesogens can change their molecular structures after the orientation. However, photoalignment of NBA requires high exposure. In contrast, LCP with cinnamic acid (CA) as a side chain requires low energy for the molecular orientation, but the generated birefringence (∆n) is small. Herein, we synthesize copolymers of CA and aldehyde-terminated mesogens to achieve highΔn LCP. Increase in the birefringence is attained via the photo alignment and molecular structural conversion.

Photorefractive effect is one of hologram formation method. In a previous study, fast photorefractive effect was observed in liquid crystals containing photoconductive chiral compounds because the macroscopic polarization called spontaneous polarization responds directly to the photo-induced electric field. In this study, we synthesized a new 8PP-2MB (2-methyl butane), which has a higher dipole moment, in order to further speed up the photorefractive effect.

We synthesized two homologous series of thioether- and ester-linked N-(4-cyanobenzylidene)aniline-containing bent-shaped dimers with even numbers of carbon atoms (n) = 2, 4, 6, 8, and 10 [CBCOOnSBA(CN) and CBOCOnSBA(CN)], in which the ester linkages in each series oppositely direct. We analyzed their phase-transition behavior using polarizing optical microscopy and differential scanning calorimetry. All the dimers formed a monotropic twist-bend nematic (NTB) phase below the temperature of conventional nematic (N) phase. The phase-transition temperatures and entropy changes of the CBCOOnSBA(CN) were lower than those of CBOCOnSBA(CN). Under UV light irradiation, their NTB and N phases transitioned to the N and Isotropic phases, respectively, which were reversible when turning the UV light off.

It has been reported bent dimers consisting of two rigid mesogenic arms linked by a flexible spacer chain with an odd number of carbon atoms form a twist-bend nematic (NTB) phase. Phase-transition behavior of liquid crystal dimers is strongly influenced by the position and number of fluorine substitutions at the mesogenic arm moieties. In this study, we synthesized novel fluorinated cyanobiphenyl-based bent dimers and evaluated their phase-transition behavior to clarify the effects of the number and position of fluorine substitutions on the phase-transition behavior, especially for the formation of the NTB phase.

The control of molecular alignment in liquid-crystalline polymer films plays an important role for developing functional materials in the field of electronics, optics, and robotics. Among the methods employed to fabricate molecularly aligned films, the photoalignment technique has attracted attention due to its non-contact feature and precise controllability. Recently, we have proposed a novel photoalignment method, termed scanning wave photopolymerization (SWaP). This utilizes molecular diffusion induced by photopolymerization as a driving force for controlling molecular alignment. However, a comprehensive understanding of the underlying mechanism of alignment behavior resulting from SWaP has not been clarified. In this study, we analyzed the fluorescence behavior of polymer films fabricated by SWaP to investigate the relationship between molecular diffusion and alignment behavior.

We synthesized two types of photo-responsive liquid crystalline (LC) block copolymers with LC copolymers containing azobenzene and cyanobiphenyl side-chains and a silsesquioxane side-chain polymer block by reversible addition-fragmentation chain transfer polymerization. The two types LC block copolymers are modified with azobenzene mesogens having alkyl and alkoxy tails. These block copolymers exhibited high LC temperature compared to each corresponding homopolymer. Microphase-separated structures of the block copolymer thin films were investigated by atomic force microscopy and grazing incidence X-ray scattering measurements. The orientation of microphase-separated structures in the thin films was controlled by linear polarized visible light irradiation under the liquid crystalline temperature. We obtained higher dichroism for the block copolymer thin films with alkoxy tails at the azobenzene side chains.

The twist-bend nematic (NTB) phase is formed by bent dimers consisting of two mesogenic structures connected by an alkyl spacer chain with an odd number of carbons. Although a terphenyl group is expected to increase the phase transition temperature and stabilize the liquid crystal phase of liquid crystal dimers, there are few examples of the terphenyl-based dimers that exhibit the NTB phase. In this study, we synthesized a new homologous series of bent dimers with a terphenyl group and clarified the effect of the terphenyl group on the formation of the NTB phase.

Recently, many kinds of peeping prevention technologies for LCDs have been proposed. Most of them can be categorized into two groups, the methods attaching additional LCDs and the special LCD structures. We propose a new kind of peeping prevention technology in which new optical films are used instead of polarizers for conventional LCDs. The optical film possesses the HAN (Hybrid Aligned Nematic) LC structure containing dichroic dye. The incident light parallel to the molecular axis of the dichroic dye is not polarized. So, the light strength cannot be controlled by the LCDs. This method can be applied to all kinds of conventional LCDs.

In this study, we attempted to realize a self-adjusting light-controlling device that can be switched by external light by adding a photoconductive material to polymer-dispersed liquid crystal (PDLC) and controlling the electrical conductivity of the PDLC by light irradiation. Ionic liquids were used as solvents for the phthalocyanine dyes. As a result, the PDLC was strongly heated by applied AC voltage, and it does not work well. As another study, a self-adjusting liquid crystal smart window based on liquid crystal electroconvection was investigated.

A new type of optical device with variable transmittance based on the incident angle direction is proposed. These devices consist of two liquid crystal devices (LCDs) with a half-wave plate between them. Hybrid aligned nematic (HAN)-type guest-host (GH) LCDs or GH-LCDs with antiparallel alignment of high pretilt angles were used. The use of a half-wave plate allowed for the control of the p- and s-waves. Using these devices, a wide range of transmittances were obtained because no polarizer was used. The newly proposed LCDs have a wide range of applications, including use on buildings, vehicles, and glasses.

Novel measurement method of liquid crystal (LC) materials in millimeter-wave (MMW) region has been investigated by using Coplanar Waveguide (CPW) fabricated with Si substrate, where intense pulsed LD light is incident on the CPW to create non-contact movable MMW reflection boundary. In this study, we fabricate a LC cell structure on the CPW and investigate the measurement method of the losses and refractive indices of LC materials. The measurement results of various LC materials are compared with those by using waveguide test cell to confirm the validity of the measurement method.

This study reports the electro-optic properties of swelling LC gels compared to polymer-stabilized LC. A polymer/LC composite system is one of the methods to achieve a fast response in the electro-optic effect of LC devices. The swelling LC gel is fabricated by polymerizing a LC-monomer/LC mixture while cooling it at a low temperature of -20 °C. The swelling LC gel exhibited high transparency in the near-infrared wavelength range (> 700 nm) regardless of the field intensity and a short decay response time on the order of tens of microseconds.

By considering an advantage of the characteristics of liquid crystal devices that allow large optical phase control, we have investigated the two-slits Young's interference experiments with an improved self-aligned device structure. In this study, we have observed detailed patterns of interference fringes using the new self-aligned liquid crystal-slit structure and the redesigned micron-width slit, and report that we have observed NOT logic of light, in which the peak intensity near the center is also inverted.

A Mach-Zehnder interferometer with an optical phase control by a twisted nematic (TN) liquid crystal (LC) device was studied. In a typical TN LC device, a change in the optical rotation state of π/2 can be obtained by applying a voltage of about 5 V with a cell thickness of several-micron. The TN cell is inserted into one optical path in the Mach-Zehnder interferometer. We obtained a pattern change when voltage was applied to the LC cell due to the change of the optical interference state. As a result, a change in the number of photons under weak light conditions is observed.

Liquid crystals (LCs), possessing both fluidity and optical anisotropic properties, exhibit interesting optical functions. In particular, homogeneously aligned dye-doped LCs change their molecular orientation by the incidence of a polarized laser beam, causing the self-focusing and phase modulation effects resulting in the formation of diffraction rings. Recently, we have discovered that polymer stabilization of dye-doped LCs drastically enhances their optical sensitivity, and that the ellipsoidal diffraction rings rotate by the irradiation with a circularly polarized beam. However, the mechanism of this rotation behavior remained unexplored. In this study, we investigated the molecular reorientation and rotation behavior of diffraction rings arising from PSLCs fabricated with several different conditions.

We designed broadband geometric phase diffractive optical elements (GPDOE) in the near infrared regime. High diffraction efficiency over 99% from 1250 nm to 2200 nm can be achieved by employing a dual-layer GPDOE made by chiral liquid crystal materials with opposite handedness. We fabricated a single-layer GPDOE, whose diffraction efficiency agreed with the calculation. The broadband GPDOE with dual-twist structure is a promising optical component for a polarization imaging system in the near infrared regime.

This work provides a liquid crystal (LC) alignment method based on the hydrophilicity and hydrophobicity of the substrate surface. This method uses photolithography and can form a hydrophilic and hydrophobic pattern on a substrate. The pattern area is formed by sulphonic azo dye and octadecyltrimethoxysilane, and these regions induce homogeneous and homeotropic alignments of LCs, respectively. The resolution of LC alignment can achieve a few micrometers. Using this alignment method, we fabricate LC zone plates and evaluate the electro-optical properties.

Liquid crystal (LC) device is one of the strong candidates for high performance THz elements because of its controllability with low drive voltage and low power consumption. Previously, we reported that hydrogen-bonded LC have excellent propertied in the THz band. We also reported that orientation pattern appears by applying high voltage to the hydrogen-bonded LC cells. We believe that this orientation pattern is applicable for diffractive devices in the THz band. In this study, we report on the diffraction properties of electrically induced orientation patterns in the hydrogen-bonded LC.

Patterned alignment of liquid crystals has been studied actively in recent years to control the behavior of light. The photoalignment method currently used for liquid crystal alignment can easily achieve uniform alignment by linearly polarized light irradiation but it is not easy to produce patterned alignment with a single exposure. In this study, we show that a Fabry-Perot resonator in which a pattern-oriented uniaxially anisotropic medium is introduced functions as a filter to obtain a linearly polarized light distribution reflecting the introduced pattern. We show that the filtered light can be used for photoalignment, making the proposed structure potentially useful as photoalignment exposure masks.

A coaxial-optical setup for laser ultrasonic measurement using photorefractive liquid crystal mixtures was fabricated. Photorefractive liquid crystal mixtures, composed of smectic-C liquid crystals, photoconductive chiral compounds, and a sensitizer, are known to exhibit a fast photorefractive effect. The principle of the laser ultrasonic measurement is that a laser pulse is shot on an object to produce an ultrasonic vibration, and then a continuous laser beam is irradiated on the object to detect the vibration using photorefractive two-beam coupling. The method can be used to investigate the internal structure of an object without contact.

It is important to investigate millimeter wave absorbance and reflectance characteristics of liquid crystal (LC) tunable metasurfaces because they can play a crucial role in current 5G telecommunication systems. Furthermore, adding a see-through function in the visible light region increases the practicality of the devices. In this work, we introduced ITO layers as grid-patterned electrodes of LC tunable absorbers. We found that the millimeter wave absorbance varied by injecting a liquid crystalline material into empty cells. In other words, the permittivity variation of the LC layer can change the millimeter-wave absorption characteristics.

Cholesteric liquid crystal elastomers (CLCE) are unique materials that combine the rubber elasticity with the optical properties of cholesteric liquid crystals (CLC). A marked feature of CLCE is that the characteristic wavelength of selective reflection of CLC is reversibly varied in response to the application and release of deformation. Exploring the mechano-optical response under various deformation modes is vital to understand comprehensively the physical properties of CLCE, and to consider their diverse deformation patterns during practical applications. In this study, we have employed four deformation types, i.e., uniaxial extension, compression, planar extension, and swelling via solvent, to characterize the optical response behavior of a CLCE film with helical axis oriented in the thickness direction.

When mixing two nematic compounds that act as an electron acceptor and donor, respectively, one can obtain higher ordered smectic phases such as SmB or SmE induced by charge transfer interactions. In this study, we investigated the anisotropic molecular motions of the induced Sm phases composed of 5CB and EBBA by means of dielectric spectroscopy. It was found that the rotation around the molecular short axis significantly depended on the mixing ratio, in which the relaxation was the slowest when the molar ratio of 5CB:EBBA was 1:3. On the other hand, the rotational relaxation time along the molecular long axis was simply given by the average values of 5CB and EBBA.

We reported that a fluorine-based liquid crystal compound having a 1,3-dioxane skeleton (CnDIO) showed an extremely large dielectric anisotropy of 10,000 or more in the ferroelectric nematic phase (NF phase). However, CnDIOs are thermally unstable above 100ºC and the temperature range in which CnDIOs exhibit the NF phase is higher than room temperature. Therefore, it is desirable to design thermally stable CnDIOs showing the NF phase at lower temperatures. In this study, we newly synthesized CnDIO analogues without 1,3-dioxanyl structures and investigated their ferroelectric liquid crystal properties. Consequently, we succeeded in extending the temperature range of the ferroelectric liquid crystal phases to the lower temperature by mixing these analogues.

The compound examined is a symmetric-core molecule with phenylbenzene (PB) at both sides of the central group and a methyl group as a side group, having a docosyloxy terminal chain, denoted MPB-22. As an effect of the side groups, we found that the Ia3d-Cub phase shifts to the low-temperature side compared to PB-22 without methyl groups. We also investigated the packing structure of the molecular cores in the Ia3d-Cub phase and found that the methyl group would be responsible for the packing structure sensitively dependent on the experienced thermal cycles.

Molecular manipulator is a method of controlling the concentration distribution of target molecules in a nematic liquid crystal containing azobenzene and target molecules, by irradiating with excitation light to induce spatial modulation of the order parameter caused by trans-cis photoisomerization of the azo molecules [1]. Since cis form azo diffused away from excitation light irradiated area, order parameter decreases outside the area. In this report, we conducted molecular manipulation in smectic and nematic liquid crystal and observed their anisotropy. These results show that the anisotropy of molecular manipulation is higher in smectic liquid crystal than in nematic liquid crystal because of high diffusion anisotropy of cis isomer in smectic liquid crystal.

We have previously observed the polymer structure by incorporating monofunctional acrylate dyes into polymers in liquid crystal/polymer composites. Furthermore, we dissolved a dichroic fluorescent dye in the liquid crystal and successfully observed the orientation azimuth angle using a confocal laser scanning microscope (CLSM), which can rotate the azimuth angle of the polarization plane freely. However, the orientation of the polymer main chain has not been visualized. In this study, the three-dimensional structure of polymer orientation was visualized nondestructively in a liquid crystal/polymer composites incorporating a bifunctional dichroic fluorescent dye by confocal laser scanning microscopy which allows free rotation of the azimuth angle of the light polarization plane.

Lyotropic chromonic liquid crystals (LCLCs) are a class of lyotropic liquid crystals (LLCs), but are generally composed of non-amphiphilic molecules. In aqueous solutions, chromonic liquid crystals form rod-like supramolecular assemblies driven by π-π stacking of aromatic rings and nanophase separation of hydrophobic and hydrophilic parts. Such chromonic aggregates tend to orient in one direction and form a liquid crystal order depending on concentration and temperature. In this study, chromonic liquid crystals with a negative charge were introduced into a polymer gel with a positive charge. The variation of the stacking order in aggregates under stretching.

Main-chain liquid crystal polyurethanes with different flexible chains were synthesized. Their thermal, orientational and mechanical properties were examined. In the main-chain liquid crystal polyurethane (LCPU-1) obtained from symmetric mesogenic diols, the reorientation of mesogenic groups was inhibited by the hydrogen bonds and formed a nematic phase in a narrow temperature range. However, the main-chain liquid crystal polyurethane (LCPU-2) obtained from asymmetric mesogenic diols exhibited an enatiotropic nematic phase in a wide temperature range. LCPU-2 gradually elongated with the application of stress. However, LCPU-1 had high impact resistance and was not stretched up to 5 MPa.

Side-chain liquid crystal polymers (LCPs) with acetyl, nitro, cyano, trifluoromethyl and methyl terminal groups into the mesogenic side chains were synthesized. LCPs have triblock spacer chains, which are composed of hexyloxy, ethylbenzoate, and aminoalkoxy units. Their thermal and orientation properties were examined. LCPs with an acetyl terminal group formed a smectic A phase or a columnar mesophase. However, LCPs with nitro and cyano terminal groups formed only a nematic phase. Furthermore, LCPs with trifluoromethyl and methyl terminal groups did not form a liquid crystalline phase.