Quantum dots (QDs) produced by liquid-phase chemical synthesis are called colloidal QDs. Introducing the development status of next-generation displays, including liquid crystals, that utilize the characteristics of this QD.
Recently, high transmittance IPS-LCD with zero-azimuth anchoring layers formed on the electrodes was suggested (OZ-IPS). But, one of the issues in OZ-IPS is very slow response, which becomes a big barrier for mass production. So, we developed a new method to control interface anchoring energy by Polymer-Sustained-Alignment (PSA) technology. The zero-azimuth anchoring layers were formed by aligned photoreactive-PI layer with photo-radical generation units and mask exposure technique. We succeeded in making OZ-IPS-cells, and controlling both transmittance and response. And we found that it was possible to form different alignment states in LC-cell by this technique.
This seminar is related to a solution / solvent cast film and its application using two super engineering plastics (liquid crystal polymer / colorless transparent polyimide) that the corresponding author has developed so far, which has been fortunately attracting attention in the smartphone market recently. We have succeed in the world's first solution of liquid crystal polymer and put it into practical use. Transparent colorless polyimide has already been adopted in the latest foldable devices. On the seminar day I will introduce the real story of the development.
Sacran, an extracellular polysaccharide of a cyanobacterium, Aphanothece sacrum, has unique structural features such as a sulfated polysaccharide having a molecular weight of more than 10 million g/mol. In addition, it was a polysaccharide having various useful functions such as high water retention, high thickening effect, liquid crystal exhibition, heavy metal adsorption, multiple helix structure formation, wound healing, and antiallergic ability. In this lecture, we will also explain the story leading up to the practical research as a highly water-retaining material using Sacran and the development of ultra-water-retaining textile, Sacray.
Hygroscopic polysiloxanes were synthesized by polycondensation reaction of silane coupling agents. A spin-coated film consisting of polysiloxane and surfactant was prepared. The film has hygroscopic capacity and the surfactant changed its phase in response to humidity. The nanostructure of the surfactant was also fixed by photocrosslinking of the polysiloxane at any humidity. The humidity-induced phase transition method enabled a new manipulation of lyotropic liquid crystal phases after organic-inorganic hybridization.
The author recently has conducted the development of novel luminescent molecules with better luminescence efficiency in molecular aggregated states. During the course of his researches, it has been revealed that fluorinated bistolane molecules showed interesting thermochemical, thermodynamic, and photophysical characteristics. Briefly, the fluorinated bistolanes were found to exhibit deep blue photoluminescence in dilute solution and in molecular aggregated phase as well as to display liquid crystalline phase through thermal phase transition. In this lecture, the detail on the fluorinated bistolane-based luminescence liquid crystals developed thus far would be disclosed.
Ionic liquids are excellent in safety due to their characteristics such as low volatility, flame retardancy, and high electrical conductivity, and are expected to be used as new materials such as battery electrolytes. A liquid crystal (LC) phase appears between an isotropic liquid state and a crystal one, and the LCs generally have fluidity with molecular ordering (anisotropy). In this study, we aim to create a novel liquid crystalline ion-conducting material by adding a solvent into the ionic liquid that has two cation sites similar to quaternary ammonium cations in the molecule.
Liquid crystal (LC) particles are fabricated from reactive mesogens possess anisotropies originating from the uniaxial alignment of rod-like molecules. We previously focused on the particles’ function from anisotropies. However, the method of “mass production of LC particles”, which is important for the application of the particles, has not been studied much. In this work, we propose mass production method like photolithography which includes selective dissolution by solvent. Therefore, we evaluated the response of ChLC film to some solvents, measuring change of reflection spectrum of film by dropped solvent.
Control of helical axis orientation in cholesteric-liquid-crystals is important to modulate optical functions, such as reflection, polarization conversion, and diffraction. In this study, we developed one-step synthetic method of mono-dispersed cholesteric-liquid-crystal microparticles. By this method, the three-dimensional helical-axis orientation in the microparticles could be first controlled. We discuss the mechanism of the helical axis orientation and their optical properties.
Contrary to the conventional understanding that molecular motion disturbs the magnetic order that depends on intermolecular interactions, some liquid crystalline compounds show an increase in magnetic susceptibility upon melting. In this presentation, we propose a model to explain this phenomenon. A molecule in liquid crystal phases can transfer the effects of the magnetic interactions with another molecule to other molecules. The coordination number of each molecule is virtually amplified hundredfold. This huge coordination number can amplify not only the magnetic properties but also various physical properties.
Ｗｅ have successfully fabricated polycrystalline thin films having uniform and flat surface morphology of liquid crystalline organic semiconductors, i.e., Ph-BTBT-10 and 8-BTBT-8, by dip-coating method at 40mm/s or more, which is 2000 times faster than that for single crystalline thin films, when coated at around their liquid crystalline temperatures . Field effect transistors fabricated with the polycrystalline thin films exhibited high mobility of over 4cm2/Vs and 5.2cm2/vs in BGBC configuration, respectively .
We have already confirmed a bulk photovoltaic effect in ferroelectric liquid crystals bearing an extended pi-conjugated unit. In this study, we examined the photovoltaic effect in the ferroelectric liquid crystals doped with fullerene derivatives in order to extend the photosensitive wavelength area to visible light and increase the power conversion efficiency.
We have established a simple coating method of polymeric organic semiconductor films onto highly hydrophobic gate dielectric surfaces and fabricated bottom-gate/top-contact type organic field-effect transistors with an active layer of liquid crystalline polymer, poly(2,5-bis(3-hexadecylthiophene-2-yl)thieno[3,2-b]thiophene). The SiO2 gate dielectric surfaces were treated with octadecyltrichlorosilane (ODTS) or coated with an amorphous perfluoropolymer (CYTOP). Their bias-stress effects were examined in vacuum and air. By changing the coating material from ODTS to CYTOP, the operational stability was significantly improved in both vacuum and air.
Production and control of 2D self-organized layers of π-conjugated molecules is a fundamental issue in organic electronics devices. The layered crystallinity is particularly important in the organic semiconductors (OSCs) because it allows to produce aligned molecular layers interfaced with gate dielectric layers, and thus, to obtain high-performance organic thin-film transistors. Recently, it was demonstrated that the layered crystallinity is considerably enhanced by the asymmetric substitution of the π-electron cores with relatively long alkyl chains. Here, we introduce our recent studies on the thin-film morphology control of these layered OSCs, and the stability of molecular packing motifs of the fabricated films.
Rod-shaped molecules based on 2-(2-hydroxyphenyl)benzothiazole (HBT) were synthesized and their liquid crystalline (LC) behavior as well as luminescent property were investigated. The synthesized molecules show a large Stokes shift, avoiding the self-absorption and resulting in the transparency in the visible range. These compounds are extremely miscible to a conventional room-temperature nematic LC up to 14 wt%, and the resultant mixtures exhibit a sufficiently large photoluminescent quantum yield up to 0.32. The key for the large quantum yield in LC is the introduction of conjugated groups into HBT that suppresses the nonradiative decay pathways in the dispersed state.
We have investigated effects of polaron-binding energy and energetic disorder of localized states on charge transport in 2-(4-propylthiobutyl)-7-phenylbenzothienobenzothiophene (Ph-BTBT-4S-3) exhibiting Smectic E phase of liquid crystal. The critical temperature Tc = 293K to determine disorder-controlled or polaron-controlled transport was experimentally obtained. Activation energy Ea = 66.6meV due to polaron binding is also obtained in high temperature range T > 293K. We demonstrate how the static disorder disturbs polaronic transport and propose the concept how we can characterize the Gaussian disorder model with small polaron regime in soft crystal.
We prepared a chiral mixture consisting of a T-shaped nematic liquid crystal, a chiral compound, reactive monomers and a photo-initiator. The mixtures exhibited BPIII and cubic BP on cooling. We obtained polymer-stabilized BPIII and cubic BP using photo-polymerization. After removing the low-molecular materials, we observed the remaining polymer networks using field-emission scanning electron microscopy (SEM). A bicontinuous gyroid-like structure was observed for the polymer scaffold from the BPIII. We discuss structure–property relationship of blue phase materials including T-shaped, U-shaped or rod-like molecule to clear the effect of molecular biaxiality on stabilizing blue phases.
We prepared a mixture of an achiral liquid-crystalline trimer, a reactive monomer and a photo-initiator. The mixture exhibited a chiral dark conglomerate (DC) phase on cooling from isotropic liquid. After being exposed to UV irradiation in the DC phase, it was heated again to isotropic liquid and then cooled to room temperature. The mixture showed the DC phase with homochirality. The supramolecular chirality was found to be amplified by the polymer network. We investigated the nanostructures of the polymer network using SEM to discuss the mechanism of chirality amplification.
Soft materials such as elastomers and liquid crystals have attracted a lot of interest because of promising application to flexible electronic devices. However, large bending of such devices still deteriorates their performance. In order to design flexible electronic devices with high mechanical durability, it is indispensable to understand the bending behavior of soft materials. In this study, we report bending analysis of a silicone elastomer through internal strain measurement with a cholesteric liquid crystal strain sensor.
We studied the local nano-structure analysis in mixtures of cholesteric liquid crystal mixture and a bent-core molecule using small-angle X-ray scattering. We obtained different types of the orientational X-ray patterns, suggesting the different types of the nano-scale phase separation. It depends on the cooling rate from the isotropic phase, so that it is related with the kinetics of phase separation process. In the gradual cooling a new structure with the smectic order stably appears, and this smectic order enhancement is considered to be caused by the B4 filament. Furthermore, it is found that the system composed of the rod-like molecules and bent-core molecules does not only causes a simple phase separation.
A mean-field theory is introduced to describe heliconical nematic (NTB), heliconical smectic-C (SmCTB), and biaxial heliconical smectic-C (SmCTB,b) phases with mirror symmetry breaking. We extend our previous theories of the NT B phase to the heliconical smectic-C phases, by taking into account one-dimensional spatial ordering of smectic layers. The calculated phase diagrams on the temperature–alkyl chain length plane show a rich variety of phase transitions: first- and second-order NTB-SmCTB transitions, etc., including tricritical, tetracritical, and multicritical points. Our theory is qualitatively consistent with an experimental phase diagram.
In chiral tilted liquid crystals, various subphases emerge as a result of competition between ferroelectricity and antiferroelectricity. So far, the antiferroelectric phase with q_T=1/2 that exists in the mixture over a wide temperature range has been called the thresholdless antiferroelectric (TLAF) phase. SHG microscope observation of the polarization reversal process, however, revealed the existence of a threshold in the change of the SH image during the electric field sweep. Thus, this phase is not “TLAF” in the bulk.
This presentation demonstrates a generic strategy for creating and manipulating the topological waves, dubbed “solitons”, created in the nematic liquid crystals. The kinetics is controlled by an electric field based on the coupling between the wave flux and elastic deformation. These results offer a playground for further development of soliton physics and applications like on-demand cargo transport.
In cytoplasmic media, various phase transitions of biopolymers such as liquid-liquid phase separation, sol-gel phase transition, and liquid crystal phase transition are observed. To understand such intracellular phase transitions from a physical point of view, we have analyzed molecular behaviors inside cell-sized droplets covered with a lipid layer as a cell model that that bridges the difference between living cells and conventional bulk systems. In this talk, we will introduce unique phase transition phenomenon of polymer mixtures caused by the cell-sized membrane confinement.
Physical properties of a liquid crystal compound which shows 10,000 of dielectric permittivity, and a relation with ferroelectricity is discussed. It is experimentally proved that the fluorinated liquid crystal molecule with dioxane group shows a ferroelectric nematic phase in which the dipole moment in the direction parallel to the molecular long axis orient unidirectionally along the director.
A liquid crystal necklace structure was fabricated where liquid crystal droplets with a diameter of several tens of micrometers were connected by a micro-tether. The necklace structure was produced by a microfluidics device and was dispersed in a polymer solution. The micro-tether was made of a complex of liquid crystal and polymer. In the presentation, in addition to the details of the liquid crystal necklace structure fabrication by a microfluidics device, we will report the elastic constant of the micro-tether, and the whispering gallery mode observed in each droplet of the necklace structure.
In a lyotropic liquid crystal, the shape of the micelle changes depending on the surfactant concentration, composition ratio, temperature, etc. We discovered that the birefringence was induced by the flow near the N-I phase transition temperature in the isotropic phase. The magnitude of the flow-induced birefringence changes depending on the flow velocity and the composition ratio of the sample. We discuss about the critical phenomena quantitatively near the N-I phase transition temperature.
We design and construct the real-time multi-angle dispersion relation DLS measurement system. We succeed in measuring the director fluctuation and local order parameter fluctuation. Furthermore, we measure the dispersion relation near second order N-I phase transition and investigate the cross-over behavior between the director and the order parameter fluctuations.
The deformation of director field in a nematic liquid crystalline droplet under an electric field was analyzed. Under a direct-current (DC) electric field, we observed that the Maltese cross pattern in the droplet deformed, moving to the positive electrode side. Flow field measurements revealed that the DC field generated a convective flow, which resulted in the movement of the pattern. We analyzed the mechanism of the director deformation based on Onsager’s variational principle; consequently, it was verified that the model, which assumes that the deformation is induced by the flow and the dielectric anisotropy, well describes the experimental results.
Nanomaterials consisting of semiconductors and noble metals are well known to exhibit characteristic properties different from bulk materials. Especially anisotropic materials have attracted great attention due to their anisotropic properties such has polarized optical properties, electron conductivity, heat transportation, and so on. It is indispensable to regulate the alignment of nanomaterials in order to develop functional devices by taking advantage of their fascinating properties. In this paper, the regulated alignment of semiconductor nanorods hybridized with nematic liquid-crystalline polymers will be presented as an example to control the alignment of anisotropic nanomaterials.
The magnetic properties of nanoparticles (NPs) are affected by interperticle interactions. Thus, formation of magnetic NPs-based periodic structure enables us to control and modulate the their properties. However, it is quite difficult to form such magnetic NPs-based structure because magnetic NPs tend to aggregate due to their strong interactions. Thus, we focused our attention on thermotropic liquid crystalline dendrons with self-assembling property. In this study, we developed the dendron-modified Fe3O4 NPs with a thick dendron layer. The self-assembling behavior and the temperature-dependent structural ordering of the resulting dendron-modified NPs has been investigated.
Measurement of the flexoelecitric coefficients e11 and e33 is important to quantify the influence of image flicker and image sticking due to flexoelectric effect. In this paper, we proposed the method to measure e11 and e33, respectively, to compare the measurement results of FFS cells with different electrode width and the simulation results of LCDmaster 2D.
We succeeded in the stabilization of Long Pitch Super Twisted Nematic (LPSTN), which has a relationship d/p (d: cell thickness, p: chiral pitch) > 2.7 by using polymer stabilization with an applied voltage near the clearing temperature. LPSTN structure is a regular STN without an applied voltage while it changes to reversed twisted nematic (RTN) over Fredericks voltage. We are going to introduce a stabilization condition of LPSTN and RTN structures with experimental and simulation data for various d/p values.
Long Pitch Super Twisted Nematic (LPSTN) has been stabilized which has a relationship d/p (d: cell thickness divided by chiral pitch) > 2.7 by polymer stabilization with an applied voltage near the clearing temperature. The LPSTN structure is a regular STN without voltage while it changes to reversed twisted nematic (RTN) over Fredericks voltage. We are going to report a stabilization condition of LPSTN and RTN structures depending on the pretilt angle and applied voltage with simulation data of Gibbs’ Free Energy.
In order to realize a holographic display with a wide viewing-zone-angle, it is necessary to reduce the pixel pitch of a spatial light modulator. Ferroelectric liquid crystal (FLC) pixels have an advantage in pixel crosstalk suppression because the ON- and OFF-state pixels in FLC devices are controlled by the driving voltages of reverse polarity. We fabricated FLC pixel arrays with a 1 × 1-μm pixel pitch using two-layered electrodes having predesigned patterns and achieved individual driving of the FLC fine pixels. Furthermore, we demonstrated a reconstruction of a holographic 3D static image with a wide viewing-zone-angle using the FLC array.
Crystal twinning of blue phase I liquid crystal has been observed experimentally. Twinning in crystals is the joining of single crystals with different crystal orientations at a constant angle. If two single crystals share a plane, it is called a twinning plane. The structure of the twinning plane of BPI twinning has not been understood. We study it by using continuum simulation based on the Landau-de Gennes theory and obtain its structure.
he chiral disc-shaped molecules exhibit various types of columnar liquid crystals. However, the effect of the molecular shape and the position of the chiral part on the molecular assembly has not been fully understood. In the present study, we analyzed the details of the characteristic orientational structure in racemic mixture of octahedral metal complexes with the chiral core using molecular dynamics simulation and gained new insights from the microscopic perspective.
To understand the mechanism of the excited-state intramolecular proton transfer emission of the fluorescent molecules doped in the nematic liquid crystals (LCs), it is of importance to investigate the correlation of the molecular structure of the guest fluorescent molecule, its miscibility in the host nematic solvents, and the fluorescent quantum yields. In this study, we performed molecular dynamics simulations for the system of the fluorescent molecules and the nematic LC molecules mixtures with different mixing ratios. For each system, we analyzed the static structure and dynamic behavior of both guest and host molecules and the concentration dependence of those physical properties.
We study the anchoring behaviors of the nematic liquid crystal confined by polymer-coated substrates by means of molecular dynamics simulations. The liquid crystal molecules are described by Gay-Berne particles and the polymers are given by Kremer-Grest model. We found that the anchoring strength between the bulk liquid crystal director and the polymer-coated substrates changes non-monotonically with the interaction between the polymer chains and liquid crystal. The weak anchoring conditions are realized when the interaction is sufficiently weak or strong.
We have developed the synthesis method of nanosheets inside amphiphilic bilayers comprising hyperswollen lyotropic lamellar phases as independent 2-D reaction fields. Here, we report the nanosheet synthesis of amorphous aluminosilicate as a common precursor of zeolites and the subsequent conversion process to a variety of zeolite nanosheets including unprecedented types.
Ion-conductive liquid-crystalline (LC) polymers have great potential applications. Herein, we report a new family of ion-conductive polymers obtained by photo-crosslinking of lyotropic columnar LC assemblies. Co-assembly of a polymerizable zwitterionic molecule and a protic ionic liquid with different molar ratio in the presence of water can induce columnar LC phases. Self-standing polymer films were obtained by in-situ photopolymerization. The conductivities of the nanostructured polymer films were 2-3 orders of magnitude higher than those of corresponding amorphous polymers prepared by the polymerization in the isotropic liquid state.
Development of organic ferroelectrics in columnar liquid crystals (FCLCs) is desired for functional materials with flexibility and low environmental load. Though FCLCs have been achieved by adjusting the molecular shapes or the hydrogen bonds, the strong intra-columnar interaction between mesogenic cores generally results in high temperatures (> 100 °C) exhibiting FCLCs. Here, a low-temperature FCLC (> 63 °C) was generated in a urea compound with racemic branched alkyl chains. Introducing the bulky chains appropriately reduced the intra-columnar interaction, and the urea compound had high fluidity even at low temperatures, exhibiting polarization switching and polarization maintenance.
Bragg-Berry cholesteric deflectors are one of the micro- or nano-patterned liquid crystals. The Bragg-Berry cholesteric deflectors exhibit unique selective reflections, unlike conventional cholesteric liquid crystals. In this study, we calculated the angular dependence, bandwidth, and polarization of selective reflection from the Bragg-Berry cholesteric deflectors by the finite difference time domain (FDTD) method.
Polymer structure and azimuthal distribution of liquid crystal director in a highly oriented polymer / liquid crystal composite film doped with a fluorescent monomer and a dichroic dye were observed using confocal laser-scanning microscope equipped with a polarization rotation unit. The initial state of the liquid crystal director in the film was uniform homeotropic alignment, but it was found that the liquid crystal directors in each domain partitioned by the pillar-shaped polymer structures are tilted in different azimuthal directions by application of an electric field. On the other hand, liquid crystal director changed as a single domain in the thickness direction under the electric field.
We simulated optical properties of liquid crystal (LC) phase gratings through combining finite difference time domain (FDTD) method and plane wave expansion technique. The LC grating element has the advantage of being electrically, continuously and variably controllable light diffraction. We mathematically expanded the electromagnetic field emitted from the LC cell by the FDTD method to the plane wave spectrum. This technique enables to calculate the diffraction efficiency and the polarization state quantitatively.
The recent increasing interest, associated with stimulated needs to remote technology due to pandemic of COVID-19, in optical sensing stems from their potential ability to gather various information about objects in a contactless manner. For remarkably improving quality of the optical sensing information, we have proposed the introduction of concept of light polarization into the optical sensing. The ‘polarization sensing system’ consists of polarization beam steering, imaging, and distance measuring systems, and the polarization gratings, which are fabricated using the photo-alignment of liquid crystalline polymers, are of grating important for realizing these systems.