研究者業績
基本情報
研究キーワード
2研究分野
1経歴
5-
2021年3月 - 現在
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2017年4月 - 2021年2月
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2007年4月 - 2017年3月
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2002年10月 - 2007年3月
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1997年4月 - 2002年9月
受賞
1-
2003年
論文
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Analytical chemistry 96(17) 6764-6773 2024年4月30日Tremendous efforts have been made to develop practical and efficient microfluidic cell and particle sorting systems; however, there are technological limitations in terms of system complexity and low operability. Here, we propose a sheath flow generator that can dramatically simplify operational procedures and enhance the usability of microfluidic cell sorters. The device utilizes an embedded polydimethylsiloxane (PDMS) sponge with interconnected micropores, which is in direct contact with microchannels and seamlessly integrated into the microfluidic platform. The high-density micropores on the sponge surface facilitated fluid drainage, and the drained fluid was used as the sheath flow for downstream cell sorting processes. To fabricate the integrated device, a new process for sponge-embedded substrates was developed through the accumulation, incorporation, and dissolution of PMMA microparticles as sacrificial porogens. The effects of the microchannel geometry and flow velocity on the sheath flow generation were investigated. Furthermore, an asymmetric lattice-shaped microchannel network for cell/particle sorting was connected to the sheath flow generator in series, and the sorting performances of model particles, blood cells, and spiked tumor cells were investigated. The sheath flow generation technique developed in this study is expected to streamline conventional microfluidic cell-sorting systems as it dramatically improves versatility and operability.
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Lab on a chip 24(2) 171-181 2024年1月17日Although droplet microfluidics has been studied for the past two decades, its applications are still limited due to the low productivity of microdroplets resulting from the low integration of planar microchannel structures. In this study, a microfluidic system implementing inverse colloidal crystals (ICCs), a spongious matrix with regularly and densely formed three-dimensional (3D) interconnected micropores, was developed to significantly increase the throughput of microdroplet generation. A new bottom-up microfabrication technique was developed to seamlessly integrate the ICCs into planar microchannels by accumulating non-crosslinked spherical PMMA microparticles as sacrificial porogens in a selective area of a mold and later dissolving them. We have demonstrated that the densely arranged micropores on the spongious ICC of the microchannel function as massively parallel micronozzles, enabling droplet formation on the order of >10 kHz. Droplet size could be adjusted by flow conditions, fluid properties, and micropore size, and biopolymer particles composed of polysaccharides and proteins were produced. By further parallelization of the unit structures, droplet formation on the order of >100 kHz was achieved. The presented approach is an upgrade of the existing droplet microfluidics concept, not only in terms of its high throughput, but also in terms of ease of fabrication and operation.
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Journal of Photopolymer Science and Technology 36(2) 101-110 2023年6月15日
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Colloids and Surfaces A: Physicochemical and Engineering Aspects 647 2022年8月20日In this study, we developed a method for fabricating conductive particles with an insulating layer on the surface, which can be applied to anisotropic conductive films. Core-shell particles were prepared from conductive nickel-plated core particles and positively charged polystyrene (PSt) shell particles carrying phosphonium groups on their surface by the heterocoagulation technique. The effect of alkyl chain lengths (ethyl, n-butyl, and n-octyl) of (4-vinylbenzyl)trialkylphosphonium chloride on the interfacial properties was investigated by surface tension measurement. Monodisperse PSt shell particles with a controlled particle size were successfully synthesized by emulsifier-free emulsion polymerization of styrene, (4-vinylbenzyl)triethylphosphonium chloride, and n-butyl acrylate. The effects of stirring time, temperature, NaCl concentration, and PSt shell particle concentration on heterocoagulation between the nickel-plated core particles and PSt shell particles were investigated. Uniform core-shell particles with a coverage of 60% could be prepared even though the heterocoagulation temperature was below the glass transition temperature and the NaCl concentration was below the critical coagulation concentration of the PSt shell particles. When the core-shell particles obtained through the heterocoagulation process were heated above the glass transition temperature of the shell particles for 6 h, a smooth polymeric insulating layer with melted shell particles was successfully formed on the surface of the nickel-plated core particles.
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Chemistry Letters 51(6) 625-628 2022年3月31日
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CHEMISTRY LETTERS 50(8) 1566-1569 2021年8月Electro-optically responsive liquid crystal (LC) nanocapsules were prepared by miniemulsion polymerization of oil-in-water emulsion monomer droplets dissolving LC compounds. As theoretically predicted based on the spreading coefficients, the choice of capsule wall-forming monomers was important for the formation of the capsule structure. The copolymerization of fluorine-containing monomers effectively suppressed the interaction between the LC compound and the capsule wall, allowing the LC molecules to repeatedly change their orientation in response to an external electric field.
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Journal of Photochemistry and Photobiology A: Chemistry 407 2021年2月15日Among the six alkyldiphenylmethanol derivatives assessed in this study, five showed persistent room temperature phosphorescence (pRTP), whereas the original diphenylmethanol (DPhHOH) did not. pRTP is a unique luminescence phenomenon that appears only in the crystalline state and is different from the luminescence produced by dispersed molecules, such as those in a glassy solvent matrix at 77 K or a polymeric matrix. The data also suggest that pRTP appears in conjunction with a specific crystal structure. The present work demonstrates that various crystal structures show pRTP regardless of the presence or absence of weak hydrogen bonds. However, nonradiative deactivation is suppressed by both intermolecular interactions and steric regulation in the crystal, such that the emission quantum yield is dependent on the crystal structure. In addition, although the molecular structure in the crystalline state necessary for the appearance of pRTP was not fully elucidated, intermolecular interactions between face-to-face and face-to-edge benzene rings appear to play a major role. Density functional theory calculations indicate that intersystem crossing is promoted in the crystalline state because the number of paths that allow this intersystem crossing is greater in a structure having weak interactions between molecules as compared to a dispersed state. DPhHOH did not show pRTP and is considered to have a structure based on the column-like stacking of multiple molecules. In contrast, the crystals that exhibited pRTP had pseudo racemic conformation in their crystals even though each molecule was achiral. In these racemic crystals, the interactions between pairs of molecules were important to the generation of pRTP.
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Colloid and Polymer Science 2021年Luminescent core–shell polymer particles carrying amino groups for covalent immobilization of enzymes were synthesized for practical applications in immunoassays. The polystyrene core particles were synthesized by miniemulsion polymerization of oil-in-water emulsion styrene droplets dissolving 2-(2-chloropropionyl)ethyl methacrylate and the europium complex emulsified with 2-methacryloyloxyethyl-N,N-dimethyl-N–n-dodecylammonium bromide. The red luminescence attributed to europium complexes embedded in the core particles was observed upon UV irradiation. The PSt-g-POEGMAx-NH2 aminated core–shell particles were prepared by surface-initiated atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMAx), followed by Gabriel synthesis. The densities of grafted chains were determined by the composition, the hydrodynamic diameters, and the fluorescence labeling method. POEGMAx-grafted chains were found to affect the dispersion stability of the particles. The nonspecific adsorption of bovine serum albumin was suppressed by the POEGMAx-grafted chains. The enzymatic activity of horseradish peroxidase covalently bound to the terminal amino groups of POEGMAx-grafted chains was evaluated by colorimetric immunosorbent assay.
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Chemistry Letters 50(1) 35-38 2021年An N, N'-diphenylurea derivative possessing six oleyloxy groups exhibited hexagonal columnar liquid crystal phases, and the columnar molecular aggregates were cross-linked with applying an electric field to produce a highly-ordered thin film which has a polarity in the thickness direction. The resulting aromatic polyurea film showed a relatively large vertical piezoelectric constant (d33 of 6.1 pm/V).
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Materials Letters 272 2020年8月1日Electroresponsive columnar liquid crystalline urea compounds, N,N’-bis(3,4,5-trialkyloxyphenyl)ureas 1 and 2 possessing six and four terminal double bonds, were photopolymerized by UV irradiation in the liquid crystal phases to give polymerized compounds, labeled P-1-Colh and P-2-Colh, that possessed a hexagonal columnar structure. Furthermore, the photo polymerization of 1 and 2 sandwiched between two indium tin oxide-deposited glass plates with applying an electric field (20 V μm−1), produced polymerized compounds, P-1-Colh-E and P-2-Colh-E, and polarized light optical microscopy clarified that the columns polymerized were aligned in parallel to the applied electric field. In addition, by the phenomenon that polar substances absorb laser light (λ = 1064 nm) and emit second harmonic generation light (λ = 532 nm), the difference in electro-response between P-1-Colh-E and P-2-Colh-E has been revealed. The former was a polymer whose macropolarity was completely fixed, and the latter was a polymer whose macropolarity was controllable by applying an external voltage.
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Advanced Electronic Materials 6(8) 2020年8月1日Axially polar ferroelectric columnar liquid crystals (AP-FCLCs) are materials in which the molecules are self-organized into axially polar columns and exhibit switching and holding of their polar directions. If the polar directions along the columnar axis can be controlled by using a nanosized electrode, AP-FCLCs have the potential to realize ultrahigh-density memory devices. Though switching polarities in columnar liquid crystal phases have been studied by many scientists, it remains difficult to realize bistable switching. In this study, it is found that replacement of the normal alkyl groups (decyl groups) with chiral groups ((S)-citronellyl groups) in an N,N’-bis(3,4,5-trialkoxyphenyl)urea realizes perfect ferroelectricity in the rectangular columnar liquid crystal phase, and it is confirmed that the phase is an AP-FCLC phase. The differences in the properties and molecular packing structures between the achiral and chiral urea compounds are investigated. Furthermore, the mechanism for achieving ferroelectricity by introduction of the chiral alkyl chains is postulated.
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ACS APPLIED POLYMER MATERIALS 2(6) 2170-2178 2020年6月The present report describes the preparation of lanthanide-doped colorless magnetic materials based on poly-beta-ketoester particles. Monodisperse poly(2-acetoacetoxy ethyl methacrylate) (PAAEM) particles were prepared by dispersion polymerization using AAEM as the monomer in the presence of a cross-linker. Because of the swelling characteristics of the cross-linked PAAEM particles in solvent, the lanthanide was effectively doped inside the particles, and the distribution of the lanthanides in the particles was visualized. By creating terbium (Tb)-doped PAAEM particles (PAAEM/Tb), which has luminescence properties in addition to magnetic properties, the relationship between efficient lanthanide doping conditions and magnetism was clarified. Because of the low coloration of lanthanides, the resulting PAAEM/Tb particles were colorless magnetic materials compared with conventional iron oxide magnetic nanoparticles. Magnetic force microscope measurements revealed that each particle exhibited magnetism. In addition, because of the high dispersibility of PAAEM/Tb particles and their colorless nature, the inkjet printing of particles and preparation of composites with commodity polymers have been demonstrated. The present technique has been shown to be widely applicable to other lanthanides instead of Tb. This versatile process enables the development of colorless functional polymeric materials with magnetic properties.
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ACS APPLIED POLYMER MATERIALS 2(5) 1800-1806 2020年5月Here, we have demonstrated the production of colorless and full-color magnetic nanoparticles based on holmium (Ho)-doped polymers, which could not be achieved with conventional dark brown iron oxide magnetic nanoparticles. The coordination of Ho, a lanthanide with low colorability and a strong magnetic moment, with a poly(2-acetoacetoxy ethyl methacrylate) brush built on the surface of submicron-sized silica particles allowed for the formation of colorless magnetic nanoparticles. Additionally, bright and full-color magnetic nanoparticles were obtained by mixing different colored magnetic nanoparticles that were prepared by copolymerization of 2-acetoacetoxy ethyl methacrylate and dye monomers. Various colors, including transparency, were demonstrated by means of the present method, which determines the presence or absence of magnetism by Ho doping. The bright and magnetically controllable colored nanoparticles presented herein may have a significant impact on practical substances and applications, such as ink and biomedical and device applications.
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Journal of Colloid and Interface Science 563 122-130 2020年3月15日© 2019 Elsevier Inc. Liquid crystal nanocapsules (LC-Nanocapsules) were prepared by miniemulsion polymerization of the oil-in-water emulsion monomer droplets dissolving the liquid crystal (LC) compounds. In order to establish the preparation conditions of LC-Nanocapsules exhibiting the liquid crystallinity, the effects of the capsule wall-forming monomers and the crosslinking agent concentration on the capsule structure were investigated in detail. The monodisperse colloidal products covered with the robust polymer shell wall was successfully prepared by the polymerization of the emulsion monomer droplets obtained through the phase inversion temperature emulsification technique using the amphiphilic block copolymer as an emulsifier. The endothermic peak was observed at the nematic-isotropic phase transition temperature (TNI) of the LC in the differential scanning calorimetry diagram of LC-Nanocapsules. The bright- and dark-field images of the dried thin films of LC-Nanocapsules spread on a glass substrate were found to appear repeatedly by the temperature change below and above TNI by polarized optical microscopic analysis. These results revealed that the LC-Nanocapsules with a complete engulfing morphology were successfully formed by the spontaneous coacervation phenomena between the crosslinked polymer and the LC with a progression of the polymerization, as theoretically predicted from the viewpoint of the spreading coefficients.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE 547 318-329 2019年7月 査読有り責任著者
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The journal of physical chemistry. B 123(19) 4324-4332 2019年5月16日By introducing an oleyl group at the end of the straight rodlike molecule, the effect of the tail shape on the liquid crystallinity, biaxiality, and lateral switching behavior of the smectic A phase was investigated. Three types of molecules possessing a fluorinated phenyl (pentafluorophenyl, 2,3,4-trifluorophenyl, or 2,3-difluorophenyl) group and a cis-octadec-9-enyl group were synthesized, and their liquid crystallinities were compared with the corresponding molecules with a straight alkyl ( trans-octadec-9-enyl or n-octadecanyl) group. In switching experiments, the molecules with a bent terminal chain showed higher spontaneous polarization ( Ps) values than those with a straight terminal chain. Further, the directional changes of the long molecular axes were suppressed for the molecules possessing a bent terminal chain. These results show that the introduction of a bent terminal chain is highly effective for stabilizing ferroelectric switching behaviors.
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Langmuir : the ACS journal of surfaces and colloids 35(16) 5574-5580 2019年4月23日Inspired by the structural coloration of anisotropic materials in nature, we demonstrate the preparation of structural color materials by the assembly of anisotropic particles. Spherical artificial melanin particles consisting of a polystyrene core and polydopamine shell were stretched asymmetrically to form uniform-sized ellipsoidal particles with different aspect ratios. The aspect ratio and assembly method of the ellipsoidal particles influence the structural coloration, indicating that the particle shape is one of the important parameters for controlling the structural coloration. The discovery of a method to control the structural color using ellipsoidal particles is useful in basic research on structural colors in nature and provides flexibility in material design and extends the application range of structural color materials.
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Chemistry Letters 48(4) 315-318 2019年A novel bisurea compound showed columnar liquid crystal phases possessing a new functionality, polarity-adjustability. Its molecular packing structures were analyzed by X-ray diffraction (XRD), and its polarity switching behavior and magnitude of the polarity were examined by electro-optic and second harmonic generation (SHG) experiments, respectively. As a result, it was revealed that the macroscopic polarity gradually increased with every ON/OFF cycle in SHG experiment applying an electric field. This strongly suggests that the anti-parallel hydrogen bonding network in each of the columns is reconstructed to syn-parallel by applying the electric field intermittently. Furthermore, it was confirmed that the reconstructed network mostly remained even once the temperature was raised to its isotropic state.
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Chemistry Letters 48(6) 551-554 2019年Herein, we present a method for controlling the surface properties of a substrate through exposure of the catechol group by acid stimulation. The results showed that the wettability and adhesion properties of the surface of the substrate can be controlled by acid treatment or UV irradiation in the presence of a photoacid generator. These findings will provide new insights into the development of materials with controlled surface properties.
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日本液晶学会討論会講演予稿集 2019 PA29 2019年<p>Ferroelectric columnar liquid crystals are materials in which the polar direction can be controlled by applying a voltage and can be maintained after removal of the voltage. In this study, we present an example of a perfectly bistable ferroelectric columnar liquid crystalline phase using a chiral urea compound. Electrical measurements show that this compound has a relatively faster response speed in the liquid crystal phase (0.19 sec) and hold the polar structure for over 10 hours. Furthermore, a helical structure in the liquid crystal phase was confirmed from the circular dichroism spectra. In addition to the intermolecular hydrogen bonding, intra-columnar interaction derived from the helical structure stabilize the polar structure.</p>
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日本液晶学会討論会講演予稿集 2019 PA59 2019年<p>Liquid crystalline urea derivatives indicate good electro-responsiveness, and their homeotropic and homogeneous alignments can be easily switched by application and removal of an external electric field. In this study, the columns of liquid crystalline ureas ware cross-linked with controlling the alignment by an external voltage application, and a cross-linked thin film sample on which the macro dipoles ware aligned in one direction was fabricated. After investigating the thermal and electrical characteristics of the thin film, application researches for piezoelectric responsive materials ware also conducted.</p>
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日本液晶学会討論会講演予稿集 2019 PB26 2019年<p>To realize ferroelectrically switchable biaxial smectic A phases, perfluoroarene-arene (PFA-A) interaction and a bent chain structure were introduced to rod-like molecules. In ferroelectric switching experiments, the molecules with a bent terminal chain showed much larger spontaneous polarization (Ps) values than those with a straight terminal chain. Further, it was clarified that directional change of the long molecular axes were suppressed in the case of the molecules possessing a bent terminal chain. From these results, it was confirmed that introduction of a bent terminal chain is highly effective for realizing the ferroelectric switching behaviors.</p>
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ACS omega 3(12) 16626-16632 2018年12月31日Biomimetic material design is a useful method for producing new functional materials. In recent years, catecholic polymers inspired from the adhesion mechanism of marine organisms have attracted attention. Here, we demonstrated the preparation of catecholic polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization of an acetonide-protected catecholic monomer, that is, N-(2-(2,2-dimethylbenzo-1,3-dioxol-5-yl)ethyl)-acrylamide (DDEA). By selecting the specific RAFT reagents, well-defined branched PDDEA and linear PDDEA were obtained. These PDDEA samples showed stronger adhesion strength after deprotection by acid stimulation compared with that before deprotection. In addition, we demonstrated the adhesion control of synthetic polymers by photoirradiation in the presence of photoacid generators, which decompose under light and release an acid.
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Photonics 5(4) 2018年12月1日By selecting the core materials and grafted-hair polymers, hairy particles with polymer brushes can create various types of functional materials. In recent years, polydopamine (PDA) particles that are obtained by polymerizing dopamine, which is an amino acid derivative, have attracted attention for various applications. Herein, we present a novel approach for creating photonic and magnetic materials from hairy PDA particles. By grafting a hydrophilic hair polymer, we have succeeded in producing photonic materials capable of structural color changes. Furthermore, we have demonstrated the preparation of magnetic materials by immobilizing holmium, which is one of the lanthanide elements, by electrostatic interactions onto a cationic hair polymer. These results demonstrate the possibility of hairy PDA particles for a wide range of applications, such as for photonic and magnetic materials.
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Langmuir : the ACS journal of surfaces and colloids 34(39) 11814-11821 2018年10月2日Polydopamine (PDA) is of interest as a mimetic material of melanin to produce structural color materials. Herein, to investigate the influence of the material composition of the artificial melanin particles on structural color, we demonstrated the preparation of core-shell particles by polymerization of norepinephrine or 3,4-dihydroxyphenylalanine, which are melanin precursors similar to dopamine, in the presence of polystyrene particles. It was revealed that the arrays of the prepared particles produce high-visibility structural color because of absorption of scattering light. Although poly(3,4-dihydroxyphenylalanine) showed the same tendency as PDA which was previous studied, polynorepinephrine can easily produce a smooth and thick shell layer compared with that of PDA, and pellets consisting of the particles showed angle-dependent structural color. Therefore, the artificial melanin particles that produce angle-dependent structural color became stable than ever before. These results indicated that material compositions of artificial melanin particles have influence on structural color, and an important finding for application as a coloring material was obtained.
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Macromolecules 51(17) 6740-6745 2018年9月11日Holmium (Ho), one of the lanthanide elements, shows a high magnetic moment. Here we present a simple, yet highly potential approach for preparing polymer-based magnetic materials from a three-dimensional polymer network composed with poly(acrylic acid) and Ho showing trivalent nature. We have successfully prepared a magnetic polymer network that reacts directly to a magnet by three-dimensionally immobilizing Ho in the polymer matrix. The present method allowed a preparation of wide range of magnetic materials using polymeric scaffolds, e.g., polymer-grafted particles and cross-linked polymer gels. As a result of the high Ho content, these materials responded quickly to the magnet. The discovery of a method to prepare magnetic materials will provide flexibility in materials design and greatly expand the scope of application of magnetic materials.
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ACS applied materials & interfaces 10(9) 7640-7648 2018年3月7日Nature creates beautiful structural colors, and some of these colors are produced by nanostructural arrays of melanin. Polydopamine (PDA), an artificial black polymer produced by self-oxidative polymerization of dopamine, has attracted extensive attention because of its unique properties. PDA is a melanin-like material, and recent studies have reported that photonic materials based on PDA particles showed structural colors by enhancing color saturation through the absorption of scattered light. Herein, we describe the preparation of three-dimensional (3D) colloidal photonic materials, such as structural color balls and fibers, from biomimetic core-shell particles with melanin-like PDA shell layers. Structural color balls were prepared through the combined use of membrane emulsion and heating. We also demonstrated the use of microfluidic emulsification and solvent diffusion for the fabrication of structural color fibers. The obtained 3D colloidal materials, i.e., balls and fibers, exhibited angle-independent structural colors due to the amorphous assembly of PDA-containing particles. These findings provide new insight for the development of dye-free technology for the coloration of various 3D colloidal architectures.
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Colloids and Surfaces A: Physicochemical and Engineering Aspects 532 564-569 2017年11月5日Some beautiful structural colorations found in nature are produced by microstructures of melanin. Polydopamine (PDA), produced by the self-oxidative polymerization of dopamine, is known as a mimetic material of melanin. Previous experiments by our group have shown that PDA-based structural color materials produced bright structural colors upon enhancing the color saturation through the absorption of light scattering. Herein, we describe the preparation of structural color films by a dip-coating of biomimetic melanin-like particles with PDA shell layers. Various parameters of the dip-coating method influencing the structural coloration were investigated in detail. Experimental results revealed that the obtained films exhibited bright and angle-dependent structural colors independent of a background color, i.e., black or white background. These findings provide new insights for the development of dye-free ink technologies.
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Liquid Crystals 44(8) 1332-1339 2017年6月21日Blue phases (BPs) obtained by doping a commercially available liquid crystalline compound (4-butyl-N-(4-ethoxybenzylidene)aniline (EBBA)) with (2R,3R)-2,3-bis(4-octyloxyphenylbenzoyloxy)-N-(hydroxydecyl)succinimide (1) were highly stabilised by the addition of a small amount of alkane diols. Especially, addition of only 0.5 mol% of octane-1,8-diol increased the BP–Iso transition temperature by 10 K and widened the BP temperature range up to 35 K. A model stabilisation mechanism based on the construction of a hydrogen bond network in each disclination zone in BPs was proposed.
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Langmuir : the ACS journal of surfaces and colloids 33(15) 3824-3830 2017年4月18日We present the ability to tune structural colors by mixing colloidal particles. To produce high-visibility structural colors, melanin-like core-shell particles composed of a polystyrene (PSt) core and a polydopamine (PDA) shell, were used as components. The results indicated that neutral structural colors could be successfully obtained by simply mixing two differently sized melanin-like PSt@PDA core-shell particles. In addition, the arrangements of the particles, which were important factors when forming structural colors, were investigated by mathematical processing using a 2D Fourier transform technique and Voronoi diagrams. These findings provide new insights for the development of structural color-based ink applications.
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ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56(16) 4598-4602 2017年4月 査読有りIn achiral rod-like molecules, a nematic phase is the most disordered liquid crystal phase, which only has onedirectional order in the direction of the molecular long axis. A dumbbell-shaped molecule (compound 3: R C6H10 @ CH=C-C6H4-CH=CH-C6H10-R, (R=nC(5)H(11))), and its liquid crystal phase (X phase) are reported, which exhibit high scattering without thermal fluctuation between two nematic phases under a polarized light optical microscope. TheXphase was investigated by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and molecular dynamics simulation. A layered structure was ascertained for which a molecular self-organization mechanism was postulated in which the super-structure is based on lateral intermolecular interlocking. A second nematic phase above the X phase consisted of "rice grain"-shaped particles.
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Colloids and Surfaces A: Physicochemical and Engineering Aspects 512 80-86 2017年1月1日We describe a facile and simple method to prepare colloidal architectures by the in situ assembly of amphiphilic diblock copolymers onto submicron-sized core particles. Polystyrene-b-poly(acrylic acid) diblock copolymers (PStmPAAn) were directly assembled onto hydrophobic silica (SiO2) core particles, forming spherical core-shell particles. By varying the surface hydrophobicity of the core particles and the compositions of the diblock copolymers, core-shell particles with tailored shell thickness were observed. Furthermore, we demonstrated the preparation of ellipsoidal particles, which containing two core particles, based on this strategy.
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高分子論文集 74(1) 54-58 2017年The structural color of Rock Pigeon feathers is produced by thin-layer interference, which occurs in the cortex layer of the barbule. Furthermore, melanin granules, which exist below the cortex layer, absorb scattered light to reduce the background reflection. In this paper, we describe the preparation of structural color materials from combined use of polydopamine-inorganic thin films (PDA/GOPTS thin film) and black particles (PDA/GOPTS particles) that mimic the coloration mechanism of Rock Pigeon feathers. A hierarchical structure of thin films and particles was created to endure the polymerization solution of DA and DA-GOPTS. The obtained materials showed beautiful structural colors and the colors were controlled by film thicknesses.
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LIQUID CRYSTALS 44(6) 956-968 2017年 査読有りNovel C-2-symmetric chiral dopant derivatives, namely, N-substituted (2R, 3R)-2,3-bis(4-(4-octyloxyphenyl)benzoyloxy)succinimides1a-h, were synthesised, and the effects of the N-substituent and imide-carbonyl groups on the helical twisting powers (HTPs) were investigated in two nematic liquid crystalline compounds, 4-n-pentyl-4'-cyanobiphenyl (5CB) and N-(4-ethoxybenzylidene)-4-n-butylaniline (EBBA). As a result, it was clarified that the bulkiness of the N-substituents has a significant correlation with the HTPs, and the imide-carbonyl group interacts strongly with the cyano group of 5CB to give high HTPs in the nematic phases. However, it is assumed that the imide-carbonyl groups of the dopants do not have strong electrostatic attractive interactions with EBBA molecules in the nematic phase to afford the moderate HTPs. [GRAPHICS] .
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Scientific reports 6 33984-33984 2016年9月23日The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers. The size of the core-shell particles was controlled by adjusting the core polystyrene (PSt) particles' diameter and the PDA shell thicknesses. The blackness and refractive index of the colloidal particles could be adjusted by controlling the thickness of the PDA shell. The arrangement of the particles was controlled by adjusting the surface roughness of the core-shell particles. This method enabled the production of both iridescent and non-iridescent structural colors from only one component. This simple and novel process of using core-shell particles containing PDA shell layers can be used in basic research on structural colors in nature and their practical applications.
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Macromolecules 49(16) 6041-6049 2016年8月23日We present a method for fabricating photonic crystals (PCs) by polymerization-induced microphase separation of block copolymers (BCPs). Molecular weight of BCP for PCs is so large that it has been difficult for conventional solution casting and annealing methods to complete the microphase separation to form periodically ordered submicron structures. Our method overcomes the difficulty by inducing the microphase separation and transitions during the polymerization, when the molecular weight of the BCPs is small enough for the microphase separation and transitions. The microphase-separated structure is then enlarged while maintaining the self-similarity. We succeeded in fabricating PCs with reflection wavelength λm ≈ 1000 nm and a full width at half-maximum Δλ = 0.05λm by living-radical bulk block copolymerization of poly(methyl methacrylate)-block-polystyrene.
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Transactions of the Materials Research Society of Japan 41(3) 301-304 2016年<p>This article describes a simple procedure to fabricate magnetically-responsive particles from as-prepared particles. Firstly, a magnetically-responsive, holmium-containing surfactant (DDAH) was prepared by mixing a commercially available surfactant and holmium(III) chloride hexahydrate. Subsequently, polydopamine (PDA) particles, which exhibit beautiful structural colors, were modified using the DDAH to afford PDA/DDAH particles. The magnetic behavior of the obtained PDA/DDAH particles was investigated. Furthermore, structural color changes of the materials prepared by PDA/DDAH particles under magnetic fields were also investigated.</p>
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Methods in molecular biology (Clifton, N.J.) 1367 137-47 2016年Glycopolymers bearing carbohydrates have an advantage in protein recognition that is attributable to the multivalent effect (cluster effect) of side-chain carbohydrates. A variety of surface-modified polymer particles have been prepared concurrently with the development of new synthetic technology. Here we describe a synthetic method of glycopolymer-grafted polymer particles by surface-initiated living radical polymerization, i.e., atom-transfer radical polymerization (ATRP) and photoiniferter polymerization, for specific lectin recognition.
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Journal of Materials Chemistry C 3(15) 3574-3581 2015年4月Biaxial smectic A (SmAb) and biaxial nematic (Nb) liquid crystal (LC) phases using achiral straight-rod molecules were realized through perfluoroarene-arene (PFA-A) and CH/F interactions. Compounds 1a, 1b and 1c, 4,4′-bis(2,3,4-trifluorobenzoyloxy)biphenyl, 4,4′-bis(2,3-difluorobenzoyloxy)biphenyl and 4,4′-bis(2-fluorobenzoyloxy)biphenyl, were synthesized. The liquid crystallinity of these compounds was investigated using polarized light optical microscopy (POM) and differential scanning calorimetry (DSC). Furthermore, the ferroelectric switching behaviors of 1a in the nematic (N) and smectic A (SmA) LC phases and 1b in the N phase were confirmed by applying a triangular wave voltage in electro-optic experiments. Then, the values of spontaneous polarization (Ps) in the LC phases of 1a were investigated as functions of frequency, voltage, and temperature. It was strongly hypothesized that the semiperfluorinated phenyl (SFP) groups rotate around the molecular long axes and change pairs in the CH/F interacting sites, and this cooperative movement of the SFP groups is repeated during the switching process. This journal is
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JOURNAL OF MATERIALS CHEMISTRY C 3(4) 720-724 2015年 査読有りA novel approach for creating non-iridescent bright structural color materials from polydopamine (PDA) black particles is presented. Two biomimetic features, melanin granules and the amorphous structures found in nature, were incorporated into these materials, consisting of PDA black particles to develop a bright and non-iridescent structural color without using any additives.
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日本液晶学会討論会講演予稿集 2015 _PA25-1_-_PA25-2 2015年We recently synthesized a chiral dopant DA (Scheme1), with two rod-like units and a rigid arched unit. It is predicted that DA thermally decomposes and to recombines through retro-Diels-Alder and Diels-Alder reaction of anthracene and fumaryl ester. In a chiral nematic phase, it is expected that these reactions proceed with a favorable enantioselectivity due to the helical alignment of liquid crystal molecules generated by DA. The purposes of this study are to pursue the behavior of DA in liquid crystal phase and to realize chirality retention in the racemization condition. The equilibrium constant K was caluculated by 1H-NMR of DA heated in d8-toluene. The mixture of DA and host-LC(figure 1) was observed by POM and the amount of DA was monitered by HPLC.
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Colloids and Surfaces B: Biointerfaces 145 152-159 2016年9月1日© 2016 Elsevier B.V. Luminescent particles have been attracting significant attention because they can be used in biochemical applications, such as detecting and imaging biomolecules. In this study, luminescent polystyrene latex particles were prepared through miniemulsion polymerization of styrene with dissolved europium complexes in the presence of bovine serum albumin (BSA) and poly(ethylene glycol) monomethoxy methacrylate as surfactants. The solubility of the europium complex in styrene has a strong effect on the yield of the particle. Europium tris(2-thenoyl trifluoroacetonate) di(tri-n-octyl phosphine oxide), which has a high solubility in styrene, was sufficiently incorporated into the polystyrene particles compared to europium tris(2-thenoyl trifluoroacetonate), which has a low solubility in styrene. The luminescence property of the europium complex could remain intact even after its incorporation through the miniemulsion polymerization. In the aqueous dispersion, the resulting particles could emit strong luminescence, which is a characteristic of the europium complex. The antibody fragments were covalently attached to BSA-covered particles after a reaction with a bifunctional linker, N-(6-maleimidocaproyloxy)succinimide. The time-resolved fluoroimmunoassay technique showed that 3.3 pg/mL of human α-fetoproteins (AFP) can be detected by using the resulting luminescent particles. An immunochromatographic assay using the resulting particles was also performed as a convenient method to qualitatively detect biomolecules. The detection limit of AFP measured by the immunochromatographic assay was determined to be 2000 pg/mL. These results revealed that the luminescent particles obtained in this study can be utilized for the highly sensitive detection of biomolecules and in vitro biochemical diagnosis.
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Colloids and Surfaces A: Physicochemical and Engineering Aspects 482 68-78 2015年10月5日© 2015 Elsevier B.V. Polystyrene latex particles with controlled size were prepared by polymerization of oil-in-water (O/W) emulsion styrene droplets obtained through the phase inversion temperature (PIT) emulsification using amphiphilic comb-like block polymers, polystyrene-b-poly[oligo(ethylene glycol) methyl ether methacrylate] (PStn-b-POEGMAm-Cl). PStn-b-POEGMAm-Cl block polymers were synthesized by sequential atom transfer radical polymerization (ATRP) of St and OEGMA. The interfacial properties of PStn-b-POEGMAm-Cl in aqueous media were investigated by means of surface tension measurement, fluorescence probe technique, and transmittance measurement. The length of hydrophobic PSt block chain was found to affect the critical micelle concentration, the micelle aggregation number, and the cloud point. O/W emulsions were obtained through the PIT process using PStn-b-POEGMAm-Cl as a surfactant by lowering the temperature of emulsions below the PIT in an ice bath. PSt particles with precisely controlled size in a range between 30 and 120nm were successfully prepared by a free radical polymerization of St droplets initiated by the water- or oil-soluble initiators. FE-SEM observation revealed that the morphology of polystyrene particles was found to depend on the relative PSt chain length of PStn-b-POEGMAm-Cl.
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COLLOIDS AND SURFACES B-BIOINTERFACES 29(1) 53-65 2003年5月The adsorption of anti-a-feto protein (anti-AFP) onto polystyrene-core-poly(N-isopropylacrylamide)-shell particles was investigated as a function of temperature, pH, and salinity. The influence of various physicochemical parameters onto the colloidal and surface properties of such stimuli-responsive particles was first studied. Then, the adsorption of anti-AFP antibody was investigated in order to point out the driving forces involved in the adsorption process. The effects of salinity, pH, and temperature demonstrated that adsorption was mainly governed by electrostatic interactions. In addition, the adsorption isotherms were analyzed on the basis of a Langmuir model leading to the determination of affinity constants. Finally, based on this adsorption study, various covalent coupling methodologies of the antibody were compared by using two different copolymers as a reactive spacer arm. The amount of chemically grafted antibody was obtained after performing the desorption step (by lowering the temperature, changing the pH, or raising ionic strength). The grafted quantity of antibody was found to be related to the adsorbed amount as a function of pH and ionic strength. (C) 2002 Elsevier Science B.V. All rights reserved.
Works(作品等)
2共同研究・競争的資金等の研究課題
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日本学術振興会 科学研究費助成事業 2021年4月 - 2024年3月
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日本学術振興会 科学研究費助成事業 2018年4月 - 2021年3月
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日本学術振興会 科学研究費助成事業 2001年 - 2002年
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日本学術振興会 科学研究費助成事業 1998年 - 1999年