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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日本液晶学会討論会講演予稿集 2015 _PA60-1_-_PA60-2 2015年Compound 1 possessing two urea groups in the molcule were designed and synthesized. Its phase transition was measured by polarized light optical microscopy and differential scanning calorimetery. In Xray diffraction measurement, it was classified that compound 1 exhibited a rectangular columnar phase. To confirm its ferroelectricity, optoelectronic and SHG experiments were carried out.
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日本液晶学会討論会講演予稿集 2015 _PB22-1_-_PB22-2 2015年To realize high density memory devices, a supramolecular compound was designed and synthesized. This compound is composed of a central urea and two trialkoxy benzoic acids possessing six polymerizable sites. After polymerization, it was expected that the polymer network stabilized the polarity of the linear urea network. To investigate the liquid-cristallinity and electro-responsiveness, polarlized optical microscope (POM), X-ray diffraction (XRD), and triangular wave voltage application are used.
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日本液晶学会討論会講演予稿集 2015 _PB23-1_-_PB23-2 2015年Mesomorphic urea compound 1 and polymerizable compound 2 were synthesized. Compound 1 exhibited a columnar mesophase. Though compound 1 showed a ferroelectric behavior, the polarity did not maintain because of the electrostatic repulsion between columns. Intercolumnar polymer network was structured in the columnar phase of 1 by addition of 2 followed by its polymerization. This network increases threshold between two polarized states. Realization of ferroelectricity is expected by that.
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日本液晶学会討論会講演予稿集 2015 _PB35-1_-_PB35-2 2015年We synthesized nonpolar liquid crystalline molecules consisting of hydrogen and carbon atoms. The rod-like compounds exhibited nematic liquid crystal phases. Despite the lack of hetero-atoms or polar groups, our nematic compounds showed electro-responsiveness in their retardation. We investigated their phase transition behaviors and liquid crystallinities by using a polarized light microscope (POM), a differential scanning calorimeter (DSC), and one- and two-dimensional X-ray diffractometers (1D-XRD and 2D-XRD).
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JOURNAL OF PHYSICAL CHEMISTRY B 118(34) 10319-10332 2014年8月 査読有りBlue phases (BPs) have received considerable attention as light shutters in the next generation of liquid crystal (LC) displays. However, no simple and efficient chiral dopant for induction of BPs of commercially available rodlike LC compounds has been reported. In this study, both (R) and (S) forms of novel chiral dopants were synthesized, showed extremely high helical twisting power values in nematic LC compounds, and induced stable BPs with a small amount of our chiral dopants (3-5 mol %). In enantiomeric excess controlled experiments, we found novel phenomena in their physical properties, such as generation of a metastable chiral nematic phase between an isotropic state and a BP.
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LIQUID CRYSTALS 41(6) 839-849 2014年6月 査読有りTo investigate the effect of the number of chiral mesogenic units and their spatial arrangement in dopant molecules on the induction of blue phases (BPs), and widening the temperature ranges of these phases, six benzene derivatives possessing (cholesteryloxycarbonyl)pentyloxy groups (monosubstituted (1), 1,2-disubstituted (2), 1,3-disubstituted (3), 1,4-disubstituted (4), 1,2,3-trisubstituted (5) and 1,3,5-trisubstituted (6) compounds) were prepared. Their helical twisting powers (HTPs) in 4-cyano-4 '-pentylbiphenyl (5CB) were proportional to the number of the chiral mesogenic units in each molecule. Furthermore, the minimum amount of the chiral dopant necessary for the induction of BPs was almost inversely proportional to its HTP value in this series.
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 449 114-120 2014年5月 査読有りThe facile preparation of nonspherical raspberry-like particles composed of a polystyrene (PSt) core and polydopamine (PDA) nodules was described. Various polymerization parameters influencing the PDA nodules were investigated in detail. It was found that raspberry-like particles were obtained in a 1:1 water/methanol solution in the presence of compounds with carboxylic acid groups, e.g., caffeic acid (CF). The raspberry-like particles obtained were characterized in terms of their size, morphology, and chemical composition using scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared (IR) spectroscopy, elemental analysis, and solid-state nuclear magnetic resonance (NMR) measurements. Finally, the formation mechanism was discussed. Because PDA may be used to cover a variety of particle surfaces, the present method has great potential for fabricating many types of raspberry-like particles. (C) 2014 Elsevier B.V. All rights reserved.
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Journal of Colloid Science and Biotechnology 3(4) 337-342 2014年 査読有り
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Transactions of the Materials Research Society of Japan 39(2) 125-128 2014年We report the first synthesis of polymer nanoparticles employing the phase inversion temperature (PIT) method using a polymeric surfactant. Oil-in-water nanoemulsions were prepared by the PIT method using amphiphilic comb-like block polymer (polystyrene-b-poly[oligo(ethylene glycol) methyl ether methacrylate], PSt-b-POEGMA) as a polymeric surfactant, and subsequently St droplets were polymerized. PSt-b-POEGMA was synthesized by sequential atom transfer radical polymerization of St and OEGMA. The interfacial property of PSt-b-POEGMA in aqueous media was investigated by surface tension measurement and fluorescence probe technique. Monodisperse PSt nanoparticles with 50 nm in diameter were obtained by a free radical polymerization of St droplets initiated by the water-soluble initiator.
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Transactions of the Materials Research Society of Japan 39(2) 157-160 2014年Herein, we describe a general and versatile procedure to fabricate hierarchically structured coatings onto material surfaces using colorless polydopamine (PDA) thin layer and polymer brush layer. Firstly, atom transfer radical polymerization (ATRP) initiator-containing colorless PDA layer was coated onto various types of material surfaces. Then, surface-initiated ATRP was conducted to produce functional polymer brush layer. This methodology will be applied to a broad range of materials to modification of surface properties. Furthermore, one-step hierarchically structured coatings of materials surface were also investigated.
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Transactions of the Materials Research Society of Japan 39(1) 57-60 2014年Herein, we describe a facile and green method to prepare fluorescent polymer particles by combined use of enzymatic miniemulsion polymerization and click reaction. Firstly, alkyne-bearing polymer particles were prepared by HRP-mediated miniemulsion polymerization of styrene with clickable surfmer (surfactant + monomer) 1. Then, azide-bearing fluorescence compound, i.e., dansyl azide compound 2, was introduced to polymer particles surface via click reaction using Cu(I) catalyst. This methodology will be applied to a broad range of azide-bearing compounds to generate functional polymer particles. Since both enzymatic miniemulsion polymerization and click reaction are conducted at room temperature in water, present method offers a practical and environmental friendly method for preparation of functional polymer particles.
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日本液晶学会討論会講演予稿集 2014 PB19 2014年<p>The ester compound consisting of pentafluorobenzene and alkoxybenzene which are electron-deficient and electron-rich aromatic rings, respectively, was synthesized. The phase transition behavior was investigated by POM and DSC. To investigate the molecular-packing structures in the liquid–crystalline states, its X-ray diffraction was measured. The CD spectra of this achiral compound in the liquid-crystalline state was measured to give a CD signal. Doping with a small amount of chiral dopant increased the intensity of the CD signal.</p>
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日本液晶学会討論会講演予稿集 2014 PA32 2014年<p>We attempted to synthesize nonpolar nematic liquid crystal crystalline compounds consisting of hydrogen and carbon atoms. We investigated their phase transition behaviors and liquid crystallinities by using a polarized light microscope (POM), a differential scanning calorimeter (DSC), and one-dimensional X-ray diffractometers (1D-XRD). In this presentation, we report the properties of nonpolar liquid crystalline compounds.</p>
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日本液晶学会討論会講演予稿集 2014 PA48 2014年<p>We have been studying electro-responsive columnar liquid crystalline ureas. In this study, we attempted realization of their ferroelectricity by introducing polymerizable groups at the terminal alkylchain of urea compounds followed by inter-columnar polymerization of the ureas. Moreover, we tried to switch the polarity of only the area where an electric field was applied in the liquid crystal phase.</p>
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RSC Advances 4(26) 13557-13564 2014年A simple but versatile microfluidic process is presented for the production of monodisperse polymeric microparticles using non-equilibrium droplets. Oil-in-water (o/w) droplets were formed within microchannels by means of a water-soluble polar organic solvent containing polymer molecules as a dispersed phase. The droplets of solvent were rapidly dissolved into the continuous phase during flow through the microchannel, whereas water-insoluble polymers were precipitated to form monodisperse polymeric particles. In this way, we successfully synthesized particles with sizes significantly smaller than that of the initial droplets, using polystyrene and poly(methyl methacrylate) as the polymer molecules and typically ethyl acetate as the polar solvent. Particles obtained under several different conditions exhibited unique non-spherical morphologies, which were caused by the translocation and segregation of the precipitated polymer and diminishing solvent-rich droplet. We confirmed that various factors influence the particle morphology, including the polymer concentration, molecular weight of the polymer, type of the polar solvent, and the presence of additives in the dispersed phase. This journal is © the Partner Organisations 2014.
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RSC ADVANCES 4(26) 13557-13564 2014年A simple but versatile microfluidic process is presented for the production of monodisperse polymeric microparticles using non-equilibrium droplets. Oil-in-water (o/w) droplets were formed within microchannels by means of a water-soluble polar organic solvent containing polymer molecules as a dispersed phase. The droplets of solvent were rapidly dissolved into the continuous phase during flow through the microchannel, whereas water-insoluble polymers were precipitated to form monodisperse polymeric particles. In this way, we successfully synthesized particles with sizes significantly smaller than that of the initial droplets, using polystyrene and poly(methyl methacrylate) as the polymer molecules and typically ethyl acetate as the polar solvent. Particles obtained under several different conditions exhibited unique non-spherical morphologies, which were caused by the translocation and segregation of the precipitated polymer and diminishing solvent-rich droplet. We confirmed that various factors influence the particle morphology, including the polymer concentration, molecular weight of the polymer, type of the polar solvent, and the presence of additives in the dispersed phase.
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SOFT MATTER 10(34) 6582-6588 2014年 査読有りA simple chiral dopant molecule (R)-1 with both rod- and arch-like units was prepared, and extremely large helical twisting powers (+123 to +228 mu m(-1)) in nematic liquid crystal phases were achieved. We have demonstrated that the introduction of an arch-like unit in addition to rod- like units is highly effective in controlling the helical molecular alignment. As an application of the dopant, induction of blue phases by addition of a small amount of it was achieved.
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Macromolecular rapid communications 34(15) 1220-4 2013年8月A free-standing polymer brush film with tailored thicknesses based on a colorless polydopamine (PDA) thin layer is prepared and characterized. The surface-initiated atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) is performed on a PDA layer with thickness of ca. 6 nm, which generated an optically transparent and colorless free-standing PHEMA brush film (1.5 cm × 1.5 cm). Because the cross-linked PDA layer is used as the base for the polymer brushes, the reported method does not require cross-linking the polymer brushes. The free-standing film thicknesses of ≈16-75 nm are controlled by simply changing the ATRP reaction time. The results show that the free-standing PHEMA brush film transferred onto a plate exhibits a relatively smooth surface and is stable in any solvent.
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POLYMER JOURNAL 45(3) 354-358 2013年3月 査読有り
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POLYMER CHEMISTRY 4(9) 2696-2702 2013年 査読有りHerein, we describe a facile method to prepare a colorless functional polydopamine (PDA) thin layer by the in situ oxidative copolymerization of dopamine (DA) and ATRP initiator-bearing DA (DA-BiBB) onto polystyrene (PSt) core particles: PSt@PDA/BiBB2. Surface-initiated ATRP of 2-hydroxyethyl methacrylate (HEMA) was performed on PSt@PDA/BiBB2 particles, followed by the removal of the template particles, which generated PHEMA capsules that were based on a colorless PDA thin layer and have tailored hollow core sizes and capsule wall thicknesses. The PDA thin layer is used as a basis for polymer brushes. The present method does not require cross-linking the polymer brushes. Furthermore, subsequent preparation of functional PHEMA capsules by post-functionalization of hydroxy groups of PHEMA chains was successful.
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Journal of Polymer Science Part a-Polymer Chemistry 51(19) 4042-4051 2013年 査読有り
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COLLOID AND POLYMER SCIENCE 291(1) 215-222 2013年1月 査読有り
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CHEMISTRY LETTERS 41(10) 1131-1133 2012年10月 査読有りThe influence of surfactant type on monomer conversion and particle size of polystyrene particles prepared by horseradish peroxidase (HRP)-mediated miniemulsion polymerization was investigated.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE 368(1) 107-114 2012年2月 査読有りThe organic/inorganic hybrid particles PSt/P(St-CPEM)(theta)-g-PDMAEMA/SiO2 were prepared by catalytic hydrolysis and subsequent polycondensation of tetraethoxysilane in the poly[2-(N,N-dimethylamino)ethyl methacrylate] (PDMAEMA) layers grafted on the PSt/P(St-CPEM)(theta) core/shell heterocoagulates. The micron-sized PSt core and the submicron-sized P(St-CPEM) shell particles bearing ATRP initiating groups were synthesized by dispersion polymerization of styrene (St) and emulsifier-free emulsion polymerization of St with 2-chloropropionyloxyethyl methacrylate (CPEM), respectively. The raspberry-shaped PSt/P(St-CPEM)(theta) heterocoagulates with a controlled surface coverage (theta = 0.51, 0.81) were prepared by hydrophobic coagulation between the core and the shell particles in an aqueous NaCl solution near the T-g of P(St-CPEM). Surface modification of heterocoagulates was carried out by ATRP of DMAEMA from the shell particles adsorbed on the core particles. Silica deposition was performed by simply adding tetraethoxysilane to a water/methanol dispersion of PSt/P(St-CPEM)(theta)-g-PDMAEMA. The SEM and TGA revealed that the resulting PSt/P(St-CPEM)(theta)-g-PDMAEMA/SiO2 composites maintain a raspberry-like morphology after deposition of silica onto the PDMAEMA layer grafted on heterocoagulates. The micron-sized, raspberry-shaped or the submicron-sized, hole-structured silica hollow particles were obtained selectively by thermal decomposition of the PSt/P(St-CPEM)(theta)-g-PDMAEMA/SiO2. The oriented particle array was fabricated by dropping anisotropically perforated silica particles onto a glass substrate settled at the bottom of a bottle filled with chloroform. Crown Copyright (C) 2011 Published by Elsevier Inc. All rights reserved.
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POLYMER CHEMISTRY 3(5) 1123-1125 2012年 査読有り
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Macromolecules 45(23) 9435-9444 2012年 査読有り
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POLYMER CHEMISTRY 3(4) 900-906 2012年 査読有り
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Carbohydrate Research 346(18) 2965-2969 2011年12月27日A new family of activated glycosidic compounds has been designed and synthesized: (2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-2- nitrophenylmethane (1). It is stable in conditions commonly used for synthesis, and it can be converted to a sugar lactone derivative merely by photoirradiation (λ = 365 nm): 2,3,4,6-tetra-O-acetyl-d-glucono-1,5-lactone (2). A mechanism for the reaction is proposed. The photochemical conversion of 1 in the presence of methanol has also been demonstrated, giving rise to methyl 2,3,4,6-tetra-O-acetyl-d-gluconate (3). © 2011 Elsevier Ltd. All rights reserved.
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EUROPEAN POLYMER JOURNAL 47(12) 2351-2360 2011年12月 査読有りPolystyrene particles bearing ATRP initiating groups, obtained by emulsifier-free emulsion polymerization of styrene (St) and 2-chloropropyloxyethyl methacrylate (CPEM), were subjected to surface-initiated activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) using glycomonomers, i.e., 4-vinylbenzenesulfonamidoethyl 1-thio-beta-D-glucopyranoside (1) and 4-vinylbenzenesulfonamidoethyl 1-thio-beta-D-lactoside (2). The glycopolymer-grafted polystyrene particles obtained Gp1 and Gp2 were shown to have hydrated graft layers of 15-65 nm in thickness on the cores of 370 nm in diameter. Gp1 and Gp2 coagulated in the presence of concanavalin A (Con A) and that of peanut agglutinin (PNA), respectively, showing highly specific response toward lectins. (C) 2011 Elsevier Ltd. All rights reserved.
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JOURNAL OF CATALYSIS 279(1) 123-135 2011年4月 査読有りOrdered layered double hydroxides (LDHs) consisting of zinc and/or copper hydroxides were synthesized and combined with aluminum or gallium. These LDH compounds were then applied as photocatalysts to convert gaseous CO2 (2.3 kPa) to methanol or CO under UV-visible light using hydrogen. Zn-Al LDH was the most active for CO2 photoreduction and the major product was CO formed at a rate of 620 nmol h(-1) g(cat)(-1), whereas methanol was the major product formed by the inclusion of Cu in the LDH photocatalysts, e.g., at a formation rate of 170 nmol h(-1) g(cat)(-1), using Zn-Cu-Ga photocatalyst. The methanol selectivity improved by the inclusion of Cu from 5.9 to 26 mol% and 39 to 68 mol%, respectively, when Zn-Al (the conversion 0.16-0.11%) and Zn-Ga LDH catalysts were used (the conversion 0.02-0.03%). Specific interaction of Cu sites with CO2 was spectroscopically suggested to enable coupling with protons and photogenerated electrons to form methanol. (C) 2011 Elsevier Inc. All rights reserved.
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 377(1-3) 63-69 2011年3月 査読有りThe organic/inorganic composites were fabricated by catalytic reduction of tetrachloroaurate ions in poly[2-(N,N-dimethylamino)ethyl methacrylate] shell layers on polystyrene core particles. The core-shell particles were prepared by emulsifier-free emulsion polymerization of styrene (St) with 2-chloropropionyloxyethyl methacrylate (CPEM) using potassium persulfate as an initiator, followed by surface-initiated activator generated electron transfer-atom transfer radical polymerization (AGET-ATRP) of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) on core particles dispersed in aqueous media. The concentration effect of both DMAEMA (x) and copper complex (y) on a shell thickness of P(St-CPEM)-g-PDMAEMA(x/y) core-shell particles was investigated by light scattering technique. The amount of grafted DMAEMA units with respect to (wrt) St was determined by H-1 NMR spectra measurement. The P(St-CPEM)-g-PDMAEMA(x/y)/Au-z hybrid particles were successfully obtained by loading with hydrogen tetrachloroaurate (HAuCl4) into the P(St-CPEM)-g-PDMAEMA aqueous dispersions. The particle size and shape of gold nanoparticles (NPs) generated by catalytic reduction in the poly[2-(N,N-dimethylamino)ethyl methacrylate] (PDMAEMA) shell layers were evaluated by both UV/vis absorption spectra measurement and TEM observation. The size and the number of gold NPs increased with increasing HAuCl4 concentration (z) below 75 mM. Interestingly, 60-80 nm sized, trigonal or polygonal, plate-like gold NPs were generated in the PDMAEMA shell by adding HAuCl4 of 100 mM. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
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15th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2011, MicroTAS 2011 3 1653-1655 2011年A simple but highly versatile microfluidic system is presented to synthesize monodisperse polymeric particles, without necessitating polymerization processes. The principle utilizes the non-equilibrium oil-in-water (o/w) droplets, of which the dispersed phase was composed of a water-soluble organic solvent and water-insoluble polymer molecules. The non-equilibrium droplets, temporary formed at the microchannel confluence, is gradually diminished as the solvent is dissolved into the continuous water phase, while the polymer molecules are precipitated and solid particles are finally formed. We successfully synthesized polymer (polystyrene and poly(methyl methacrylate)) particles with sizes much smaller than the initial droplet size, and found that the polymer concentration and the molecular weight are the critical factors dominating the spherical/nonspherical particle morphologies.
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POLYMER JOURNAL 42(12) 952-955 2010年12月 査読有り
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 369(1-3) 240-245 2010年10月 査読有りIn this paper, a simple method for fabrication of glycopolymer hollow particles was demonstrated. The P(St-CPEM)-g-PVBSAELA core-shell particles were prepared by emulsifier-free emulsion polymerization of styrene (St) with 2-chloropropionyloxyethyl methacrylate (CPEM) using potassium persulfate as an initiator, followed by surface-initiated activator generated electron transfer-atom transfer radical polymerization (AGET-ATRP) of a styrene derivative bearing a lactose residue, i.e., N-2-4-(vinylbenzenesulfonamido)ethyl lactobionamide (VBSAELA). Dynamic light scattering measurement showed that the P(St-CPEM)-g-PVBSAELA core-shell particles possess graft layers of ca. 160 nm in thickness on the P(St-CPEM) core of 455 nm in diameter. By taking advantages of large difference in solubility between the PSt-based core and the PVBSAELA shell, the submicron-sized PVBSAELA hollow particles were obtained through a selective extraction of the core part from the P(St-CPEM)-g-PVBSAELA particles in tetrahydrofuran. The hydrodynamic diameter of the resulting hollow particles decreased by 15% compared to that of the corresponding core-shell particles. Finally, the micron-sized, raspberry-shaped, PVBSAELA hollow particles were successfully fabricated by a sacrificial dissolution of the PSt-based components from the PVBSAELA-grafted, core/shell heterocoagulates. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE 347(1) 62-68 2010年7月 査読有りOrganic/inorganic composites were prepared by catalytic hydrolysis and subsequent condensation of tetraethoxysilane (TEOS) in a shell layer of core-shell polymer particles. First, core-shell particles were prepared by emulsifier-free emulsion polymerization of styrene (St) with 2-chloropropionyloxyethyl methacrylate (CPEM) using potassium persulfate as an initiator, followed by surface-initiated activator generated electron transfer-atom transfer radical polymerization (AGET-ATRP) of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA). Dynamic light scattering revealed that hydrodynamic diameter of the particle increased from 482 to 931 nm after AGET-ATRP of DMAEMA. The amount of grafted DMAEMA was determined to be ca. 10 mol% with respect to (wrt) St by H-1 NMR. Second, the composite particles were prepared by adding TEOS into a water/methanol dispersion of the P(St-CPEM)-g-P(DMAEMA). The P(St-CPEM)-g-P(DMAEMA)-SiO2 composite particles containing ca. 50 wt.% of silica wit the total weight were obtained. Hollow silica shell particles were also obtained by extraction of polymer components from the composites with tetrahydrofuran. Crown Copyright (C) 2010 Published by Elsevier Inc. All rights reserved.
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COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 356(1-3) 169-175 2010年3月 査読有りCore-shell coagulates were prepared by hydrophobic heterocoagulation between non-charged poly(methyl methacrylate) (PMMA) core and cationically charged polystyrene (PSt) shell particles. Addition of NaCl and elevation of coagulation temperature to the vicinity of the glass transition temperature (T(g)) of the shell particles are found to be keys to successful heterocoagulation. Fluorescence resonance energy transfer (FRET) experiments using pyrene-labeled core and naphthalene-labeled shell particles showed that interdiffusion of the polymer chains at the interface between the core and shell particles is most effective when coagulates were prepared at or slightly above the T(g)s of both core and shell particles. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
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COLLOIDS AND SURFACES B-BIOINTERFACES 71(2) 194-199 2009年7月 査読有りGrafting of a styrene derivative bearing a lactose residue, i.e., N-2-4-(vinylbenzenesulfonamido)ethyl lactobionamide (VBSAELA), onto polymer latex particles was carried out in aqueous media by activator generated electron transfer atom transfer radical polymerization (AGET ATRP). The core polymer latex particles having alpha-chloroester groups as ATRP-initiating groups were prepared by miniemulsion polymerization of styrene and 2-chloropropionyloxyethyl methacrylate (CPEM) in the presence of a polymerizable surfactant, i.e., N,N-dimethyl-N-dodecyl-N-2-methacryloyloxyethylammonium bromide (C12Br). AGET ATRP was initiated with tris[(2-pyridylmethyl)amine] copper (II) dichloride and L-ascorbic acid. Dynamic light scattering (DLS) revealed that the P(St-CPEM)-g-P(VBSAELA) particles possess graft layers of 10 nm in thickness on the core particles of 91 nm in diameter. Critical coagulation concentration measurement revealed that the dispersion stability of the particles in water increased due to hydrated P(VBSAELA) shell layers. Adsorption of bovine serum albumin (BSA) onto the particles was considerably suppressed by the hydrated shell layers. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
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Journal of Colloid and Interface Science 327(1) 58-62 2008年11月1日Miniemulsion polymerization of styrene (St) in the presence of a hydrophobe (hexadecane:HD) using a cationic polymerizable surfactant (N, N-dimethyl-N - n-dodecyl-N-2-methacryloyloxyethylammonium bromide:C12Br) and a cationic initiator (2,2′-azobis(2-amidinopropane) dihydrochloride:V50), called St/C12Br/V50 hereafter, proceeded efficiently compared with that using sodium dodecyl sulfate (SDS) and potassium persulfate (KPS), i.e., St/SDS/KPS, providing monodisperse polystyrene latex particles with a narrower particle size distribution. In St/C12Br/AIBN, where an oil-soluble initiator, i.e., 2,2′-azobisisobutyronitrile (AIBN), was used in place of V50, little changes in polymerization kinetics or in particle size distribution were observed, while a significant drop in polymerization rate and a broad particle size distribution were observed with St/SDS/AIBN. A polymerizable pyrene derivative (1-pyrenylmethyl methacrylate: PyMMA) was quantitatively incorporated into monodisperse latex particles in St/PyMMA/C12Br/V50 compared to pyrene (Py) in St/Py/C12Br/V50. Contrary to our expectation, however, increased excimer emission was observed with St/PyMMA/C12Br/V50 particles, indicating less evenly distributed pyrene chromophores in the particles. The fluorescence lifetime of pyrene chromophores in St/Py/C12Br/V50 particles was determined to be 286 ns, which was 17 times longer than that of pyrene in THF solution. Crown Copyright © 2008.
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Polymer Preprints, Japan 55(2) 3949-3950 2006年Self-assembled monolayers (SAMs) possessing positively and negatively charged groups have received much attention to resist the non-specific adsorption of proteins from buffer solutions. In this study, adsorption behaviors of bovine serum albumin (BSA) on amphoteric polymer particles were investigated from the viewpoint of surface properties of colloidal particles. Amphoteric polymer particles were prepared by following two methods (i) a combination of emulsifier-free emulsion copolymerization of styrene with sulfobetaine type monomer (3-[N,N-dimethyl-(2-metacryloyloxyethyl)-amino]- propane-1-sulfonic acid, AMPS) and shot growth process, (ii) activator generated by electron transfer for atom transfer radical polymerization (AGET-ATRP) on core particles with chlorobenzyl groups by using CuI/II/ligand-ascorbic acid as a initiator system. It was shown that each amphoteric polymer particles has negatively charged surface and that magnitude of zeta-potential depend on charge type of initiator. It was also indicated that adsorption of BSA onto polymer particles was a Langmuir type adsorption. Non-specific adsorption of BSA onto polymer particles was effectively suppressed by a construction of amphoteric polymer shell layers.
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Polymer Preprints, Japan 55(1) 1194 2006年Core-shell latex particles with a core of polystyrene and a shell of hydrophilic polymer chains were prepared by Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (AGET-ATRP). The core particles were prepared by emulsifier free emulsion copolymerization of styrene and 4-chloromcthyl styrcnc. The hydrophilic shell layer is constructed by surface initiated ATRP of hydrophilic monomethoxypoly(et.hylene glycol) methacrylate, M(PEG9). The activator. Cu(I)Cl, was generated by reduction of Cu(II)Cl 2 by using ascorbic acid as a reductant. It is indicated that polymerization of hydrophilic M(PEG9) was initiated from chlorobenzyl groups on the surface of core particles, as 1H NMR spectra revealed that signals of grafted PEG chains at 3.6 and 3.4 ppm were appeared and that significant changes in signals of chlorobenzyl group at 4.5 ppm were not observed. Critical coagulation concentration of core-shell particles was less than that of core particles. Colloidal characteristics will be discussed from the view point of ζ potential.
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Polymer Preprints, Japan 55(1) 1145 2006年It is necessary to have a detailed knowledge of film formation mechanism in the fields of industry such as paintings and adhesives. In this study, the mutual penetration process of polymer chains between polymer particles were investigated by fluorescence technique. Reactive fluorecence polymer particles were prepared by mini-emulsion polymerization of styrene with hcxadecyl methacrylate, glycidyl methacrylate, 2-vinylnaphthalene or (1-pyrenyl)methyl methacrylate mini-emulsificated in the aqueous solutions of polymerizable surfactant methaeryloyloxyethylalkyl(N,N-dimethyl)ammonium bromide by using 2,2'-azobis(2 -amidinopropa.ne)dihydrochloride. Polymer particle films with different compositions were prepared by drying of fluorescence particle dispersions spread on the quartz plate at room temperature. It was shown that, relative emission intensity of pyrene to naphthalene (Ipy/I nap) increased after heating particle films over 150°C for several hours. The dependence of a mutual penetration of polymer chains on temperature, polymer composition will be discussed in terms of energy transfer efficiency.
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Polymer Preprints, Japan 55(1) 1137 2006年Distributions of functional materials in polymer particles were investigated in terms of emission behavior of pyrene. Mono-dispersed fluorescence polymer particles with ca 100 nm in diameter were quantitatively prepared by O/W type of mini-emulsion polymerization of styrene with polymcrizable surfactant, N-dodecyl-N,N-dimethyl-2-methacryloyloxyethylammonium bromide, by using V-50 as an initiator. Relative emission intensity of excimer to monomer (IE I M) decreased with increasing of hexadecane concentration over 5 mol% to styrene, which indicates that Ostwald ripening was effectively suppressed. It was shown that fluorescence lifetime of pyrene incorporated in polymer particles was determined to be 280 ns, which is 16 times longer than that in THF solutions. Decreases in IEI / I M in particles prepared by seeded emulsion polymerization was interpreted by considering of monomer diffusion to pre-formed excimer sites in seed particles.
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Polymer Preprints, Japan 54(1) 1031 2005年Emulsifier-free emulsion polymerization conditions for cationic latex particles with a core of polystyrene and a shell of poly(ethylene glycol) (PEG) chains were investigated using V-50 as the initiator. In this study, acrylate and methacrylate monomers functionalized with a different length of a PEG side chain, namely A(PEG)n and M(PEG)n, respectively, were used as hydrophilic shell layer forming monomers. Micelle aggregation properties were characterized in terms of the emission intensity ratio of the first to the third peak (I1/I3) of pyrene in aqueous PEG-monomer solutions. I1/I3 decreased at 2.0 mM with increasing of the PEG-monomer concentration and became 1.0 at the plateau region above 10 mM, indicating that PEG-monomers tend to form loosely packed aggregates at higher concentration in aqueous media. It was demonstrated that latex particles were prepared by emulsion polymerization at 1.0 mM of the PEG-monomer concentration, even though well-defined particles could not be obtained below and above 1.0 mol% of PEG-monomer concentration. Finally, amino-functionalized core-shell polymer particles with a diameter of 180 nm were successfully prepared by emulsion copolymerization of styrene with A(PEG)23 and 2-aminoethylmethacrylate.
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Polymer Preprints, Japan 54(1) 1040 2005年Polymer particles hybridized with gold colloids were prepared by mini-emulsion polymerization of styrene in the presence of amphiphilic comb-type polyurethane bearing poly(ethylene glycol) (PEG) chains as an emulsifier. Nonionic polyurethanes were prepared in a two-stage reaction. PEGylated diol compounds were firstly synthesized by Michael addition between diethanolamine and acrylate monomers with a PEG side chain. Polyurethanes were prepared by dissolving isophorone diisocyanate and PEG-functionalized diol compounds in 1,4-dioxane in the presence of dibutyltin(IV)dilaurate as a catalyst. Gold nano-particles were obtained by simply mixing aqueous solutions of polyurethane and HAuCl4 at room temperature for 12 h. With the increasing of polyurethane concentration from 1.0 to 3.0 mg/dL, absorption peak top (λmax) decreased from 542 to 525 nm, which indicated that gold colloids (15 nm in diameter) with a narrow size distribution were successfully prepared. Opaque purple latices were quantitatively obtained by mini-emulsion polymerization of styrene in the presence of colloidal gold particles in the aqueous polyurethane solutions by using AIBN. No significant changes in λmax of hybridized polymer particles dissolved in CHCl 3 solutions suggested that gold colloids kept their original size after the mini-emulsion polymerization process.
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Polymer Preprints, Japan 54(1) 1032 2005年Emulsifier-free emulsion polymerization conditions for anionic latex particles with a core of polystyrene and a shell of poly(ethylene glycol) (PEG) chains were investigated using KPS as the initiator. In this study, methacrylate monomers functionalized with a different length of a PEG side chain, namely M(PEG)n, were used as hydrophilic shell layer forming monomers. Core-shell polymer particles with a diameter of 630, 620 and 390 nm were successfully prepared by emulsion copolymerization of styrene with M(PEG) 2, M(PEG)9 and M(PEG)23, respectively. Dispersion stability of these particles in MgSO4 solutions are evaluated from the viewpoint of n-value. Critical coagulation concentration for P(ST-MAc) was determined to be 7.0 mmol/L. n-value for P(ST-MAc) decreased with increasing MgSO4 concentration above ∼10-2 mol/L, indicating that the size of scatterers increased by coagulation. On the other hand, n-value for P(ST-MAc-M(PEG))s increase with increasing MgSO4 concentration. It suggests that the sizes of particles decreased with increasing MgSO4 concentration, caused by shielding negative charges in the hydrophilic shell layers. Adsorption behaviors of nonionic surfactant and the other colloidal properties are also discussed in terms of hydrophobic interactions.
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Polymer Preprints, Japan 54(1) 1035 2005年Optimum conditions for mini-emulsion polymerization were investigated in terms of styrene conversion and the emission behavior of pyrene. The crude emulsions of monomer droplets containing hexadecane as hydrophobe in the aqueous surfactant solution were mini-emulsificated by the ultrasonic homogenizer. The mini-emulsions of styrene were polymerized by using water-soluble initiator KPS or oil-soluble AIBN. Polymer particles were successfully obtained with high dispersion stability by using KPS. contrary to the case of AIBN. These results suggest that radical recombination restricted the propagation in monomer droplets. Relative emission intensity of monomer to excimer of incorporated pyrene decreased as increasing of hexadecane concentration above 5 mol% to styrene, which indicate that monomer diffusion degradation (Ostwald ripening) were effectively suppressed by hydrophobe. Finally, porphyrin derivative, 5,10,15,20-tctratolylporphyrin (TTP) were incorporated into polymer particles to obtain opaque purple laticcs which have a sharp fluorescence emission around 650 nm with the excitation at 420 nm. While 5 mol% of pyrene was quantitatively incorporated into polymer particles, only 0.175 mol% of TTP was introduced. It seems that finely dispersion of chromophores in monomer droplets plays an important role for preparation of dye-doped latices.
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Polymer Preprints, Japan 54(2) 4330-4331 2005年In this study, we propose the novel particle assembling method for fabrication of 3-dimensionally ordered composite polymer aggregates by using colloidosomes as templates. The cationic latex particles used as an emulsifier for oil droplets in aqueous media were synthesized by emulsifier-free emulsion polymerization of styrene (ST) with N,N-dimethyl-N-alkyl-2- methacryloyloxyammonium bromide (CnBr) and glycidylmethacrylate (GMA) using V-50 as an initiator. The O/W type of emulsions were prepared by vigorous stirring of the mixture of oily hexadecane (HD), ST or MMA in water containing 1 wt% of latex particles. Dispersion stability of emulsions prepared by HD with P(ST-C8Br-GMA) colloids was improved by addition of 10 mol% to HD of hexadecylamine into HD oil phase to obtain the micrometer sized aggregates partially coated with polymer particles, whereas no stable emulsions were obtained in the absence of additives. It would be possible that the surface of reactive P(ST-C8Br-GMA) particles was anisotropically modified through a reaction between epoxy groups and amine compounds at the oil/water interface provided by colloidosomes. SEM observation revealed that composite aggregates covered with a single layer of P(ST-C8Br) particles were successfully fabricated by polymerization of MMA core droplets by using AIBN as an initiator in the presence of particular surfactants.
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Polymer Preprints, Japan 54(2) 2989-2990 2005年Mechanisms of mini-emulsion polymerization were discussed in terms of monomer conversion and the emission behavior of pyrene feeded in styrene. The crude emulsions of monomer droplets containing hexadecane as hydrophobe in the aqueous surfactant solution were mini-emulsificated by the ultrasonic homogenizer. Polymer particles with high dispersion stability were obtained by using water-soluble KPS, contrary to the case of oil-soluble AIBN. These results suggest that radical recombination restricted the propagation inside of oil droplets. Relative emission intensity of monomer to excimer (I e/Im) of pyrene incorporated in polymer particles decreased as increasing of hexadecane concentration above 5 mol% to styrene, indicating that monomer diffusion degradation (Ostwald ripening) were effectively suppressed by hydrophobe. Increase in pyrene concentration resulted in higher Ie/Im arisen from pre-formed dimers in monomer droplets. Excitation of naphthalene enhanced the fluorescence intensity of pyrene individually incorporated in polymer particles, which is indicative of Förster type of energy transfer occurring between polymer particles containing fluorescence probes.
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Polymer Preprints, Japan 54(2) 3327-3328 2005年Emulsifier-free emulsion polymerization conditions for anionic and cationic latex particles with a core of polystyrene and a shell of polyethylene glycol) (PEG) chains were investigated using KPS and V-50, respectively, as the initiator. In this study, methacrylate monomers functionalized with a different length of a PEG side chain, namely M(PEG)n, were used as hydrophilic shell layer forming monomers. Anionic core-shell polymer particles with a diameter of 630, 620 and 390 nm were successfully prepared by emulsion copolymerization of styrene with M(PEG)2, M(PEG)9 and M(PEG)23, respectively. Dispersion stability of these particles in MgSO4 solutions are evaluated from the viewpoint of n-value and stability factor (W). Shrinkage of hydrophilic shell layer caused by shielding negative charges by added salt was observed from n-value. The n-value for P(ST-MAc-M(PEG))s increased with increasing MgSO4 concentration, at first, and then decreased above the critical coagulation concentration (CCC). The CCC for P(ST-MAc-M(PEG))s were very high (∼1 mol/L) and comparable value obtained from n-value and stability parameter. In contrast, shrinkage of hydrophilic shell layer was not observed for cationic core-shell polymer particles. Adsorption behaviors of nonionic surfactant and the other colloidal properties are also discussed in terms of hydrophobic interactions.
主要なMISC
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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