Publications by authors named "Hiroshi Kakiuchida"

Polarized optical microscopy (POM) images of polymer network liquid crystals (PNLCs) were first analyzed using a pretrained machine learning model for feature extraction and hierarchical clustering. The analyses worked well in predicting and improving the thermoresponsive changes individually in direct luminous and hemispheric solar transmittance, both of which are crucial properties of energy-saving smart windows. The features of a 1280 × 1920-pixel color POM image were extracted by the latest pretrained algorithm, EfficientNet-B7, as a 2560-dimensional vector and then reduced into a two-dimensional space for clustering and visualization using the uniform manifold approximation and projection (UMAP) algorithm while efficiently preserving the global structures of the distance relationship in a high-dimensional space.

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Molecular interactions between liquid crystals (LCs) and reactive mesogens (RMs) at temperatures across the phase transition regions were comprehensively studied during photopolymerization-induced phase separation (PPIPS) beginning with raw mixtures until the formation of polymer network liquid crystals (PNLCs). Then, the molecules were found to be nonuniformly more and less mobile in response to temperature as PPIPS progressed. Optical birefringence and infrared absorption were carefully measured throughout PPIPS, using 4-cyano-4'-hexylbiphenyl (6CB) and 1,4bis-[4-(3-acryloyloxypropyloxy) benzoyloxy]-2-methylbenzene (RM257) as typical LCs and RMs.

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Background: Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, , the visceral nucleus is an opaque organ located at the posterior end of its alimentary system, but this organ has a mirrored surface to conceal its internal opaque tissue.

Results: Our ultrastructural observation proved that the cortex of the visceral nucleus comprised a stack of thin cellular lamellae forming a Bragg reflector, and the thickness of lamellae (0.

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This study examined the thermal response of polymer-dispersed liquid crystal (PDLC) diffusers, patterned using a two-lens imaging system. Optical modulation was achieved by modifying the PDLC transmittance using temperature-induced changes to liquid crystal (LC) orientation. PDLCs with controllable scattering properties were obtained by irradiating LC-polymer composites with laser speckle patterns.

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Surface modifications for easy removal of liquids and solids from various metal surfaces are much less established than for silicon (Si) or glass substrates. Trimethylsiloxy-terminated polymethylhydrosiloxane (PMHS) is very promising because it can be directly immobilized covalently to a wide variety of metal surfaces by simply heating neat PMHS liquid, resulting in a film showing excellent dynamic omniphobicity. However, such PMHS films are easily degraded by hydrolytic attack in an aqueous environment.

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Polymer network liquid crystals (PNLCs) capable of thermoresponsive change in reflective scattering were fabricated using a self-organization technique called photopolymerization-induced phase separation. These PNLCs exhibit nonscattering states at temperatures τ below the nematic-to-isotropic (NI) phase transition temperature τ but reflective scattering states at τ values above τ. The magnitude of change of optical clarity is 80% and of solar transmittance is 20% in PNLCs with a thickness of 50 μm.

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A simple nonuniform irradiation method for photopolymerization-induced phase separation (PPIPS) was developed to produce unconventional mesoscale domain structures composed of liquid crystal (LC) and reactive mesogen (RM) phases. The LC/RM phase formations and their molecular orientation ordering through PPIPS were comprehensively investigated as a function of LC/RM molar ratio, curing temperature, and the use of uniform or nonuniform irradiation. Then, two different optical-anisotropic structures that can cause normal- or reverse-mode thermoresponsive light attenuation were formed by nonuniform irradiation at different curing temperatures at the same molar ratios.

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Various metal (Al, Ti, Fe, Ni, and Cu) surfaces with native oxide layers were rendered "omniphobic" by a simple thermal treatment of neat liquid trimethylsiloxy-terminated polymethylhydrosiloxanes (PMHSs) with a range of different molecular weights (MWs). Because of this treatment, the PMHS chains were covalently attached to the oxidized metal surfaces, giving 2-10 nm thick PMHS layers. The resulting surfaces were fairly smooth, liquid-like, and showed excellent dynamic omniphobicity with both low contact angle hysteresis (≲5°) and substrate tilt angles (≲8°) toward small-volume liquid drops (5 μL) with surface tensions ranging from 20.

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Polyurethane (PU)-based transparent and flexible ionogels, showing unusual thermo-responsive optical properties, were successfully prepared by mixing PU-precursor and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI). Although the initial ionogels were transparent at room temperature, significant increases in opacity were observed with increasing temperature up to 120°C, because of macroscopic phase separation of the PU-matrix and hydrophobic EMIM-TFSI. In addition, the optical transition temperature could be arbitrarily controlled simply by varying the mixing ratio of EMIM-TFSI within the PU-matrix.

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Background: Invisibility in the water column is a crucial strategy for gelatinous zooplanktons in avoiding detection by visual predators, especially for animals distributed in the euphotic zone during the daytime; i.e., surface dwellers that do not undergo diel vertical migration.

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We first fabricated holographic polymer-dispersed liquid crystals (HPDLCs) that produce multiple Bragg diffractions with different polarization states for every angle of incidence, through a photopolymerization-induced phase separation by one-time interferential exposure. The polarizations of the Bragg diffractions were well-controlled at individual wavelengths in the fabrication process by the compositional ratio of LCs to monomers. The raw mixtures of extremely low-functionality monomers having very different viscosities were used to reduce the domain size in phase separation and subsequently to form elaborate periodic structures of the LC and polymer phases.

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Background: Tunic is a cellulosic, integumentary matrix found in tunicates (Subphylum Tunicata or Urochordata). The tunics of some ascidian species and pelagic tunicates, such as salps, are nearly transparent, which is useful in predator avoidance. Transparent materials can be detected visually using light reflected from their surfaces, with the different refractive indices between two media, i.

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Optical diffractometry is proposed as a practical method of quantitatively analyzing the microscopic structural origins of a wide range of highly efficient and linearly polarized optical diffraction grating produced from holographic polymer-dispersed liquid crystal. The structure is organized by a spatially periodical distribution of submicrometer-scale liquid crystal (LC) droplets in a polymer matrix. Six independent Bragg diffraction spectra were obtained at two orthogonal polarization states at temperatures below, at, and above the nematic-to-isotropic phase transition point.

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A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed LC, is fabricated by a photo-induced phase separation technique using LC composites with different physical properties, such as refractive indices and clearing points. Effects of thermal modulation on diffraction properties of LC composite gratings are experimentally investigated in the viewpoints of polarization and temperature dependences. The diffractions based on the change of refractive index induced by the nematic-isotropic transition of LCs with the increase of temperature are applied for a holographic image reconstruction.

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Orientation-controlled anisotropic diffraction gratings are realized by interferometric exposure using composite materials of nematic liquid crystals (LCs) and LC diacrylate monomers. The anisotropic diffraction properties in volume gratings, which dominantly diffract p- or s-polarized light, are shown to be controlled by the rubbed directions of the alignment layers under the control of the photopolymerization temperature. Images of the fringe patterns observed by polarization microscopy show the effects of the alignment layers on the LC orientation during grating formation.

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The structure and viscoelastic properties of an organic-inorganic hybrid system composed of an organically modified polysiloxane network were examined, and the influence of organic groups on elastic-modulus variation by heat treatment was studied. The increase in the number of phenyl (Ph) groups per silicon decelerates the increase in elastic modulus; the substitution of the Ph group for a methyl (Me) group accelerates it. The system basically consists of R4-mSi[O-]m/2 units, where R is the organic group.

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The relationships between the viscoelastic and structural properties of glass-forming materials with polysiloxane bonds, which serve as network formers, and phenyl groups, which act as network terminators, are examined based on shear viscoelasticity, (29)Si MAS NMR, and GPC measurements during the early stages of the network-forming process. The viscosities of the present samples do not depend on the frequency at temperatures up to 200 degrees C, suggesting that the origin of the viscous flow does not include intermolecular entanglement. According to the results of the strain dependence of the elastic modulus, the bridging-oxygen number, and molecular weight, the present polysiloxane system has a complex structure, or distribution of various-sized molecules composed of a polysiloxane network with various dimensionalities, and furthermore an elementary process of the viscosity is simple flow of these molecules.

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