Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
-butadiene) rubbersYamaguchi, Daisuke; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*; Noda, Yohei*; Koizumi, Satoshi*; Hashimoto, Takeji*
Macromolecules, 50(19), p.7739 - 7759, 2017/10
Times Cited Count：14 Percentile：48.82(Polymer Science)We elucidated the spatial distribution of filler particles in cross-linked poly(styrene--butadiene) rubbers (SBR) developed under a typical fillers/rubbers compounding process as one of dissipative structures formed under a stress field imposed on the given system. The dispersion state of the fillers in SBR was clarified on the basis of hierarchical structures consisting of five structure levels. More specifically, it has the following characteristics depending on the specific interactions: Small, compact clusters build up compact mass-fractal structures, while large, loose clusters build up open mass-fractal structures.
Yamaguchi, Daisuke; Miyamoto, Nobuyoshi*; Fujita, Takako*; Nakato, Teruyuki*; Koizumi, Satoshi; Ota, Noboru*; Yagi, Naoto*; Hashimoto, Takeji
Physical Review E, 85(1), p.011403_1 - 011403_15, 2012/01
Times Cited Count：21 Percentile：75.06(Physics, Fluids & Plasmas)Phase transition of aqueous colloidal dispersions of charged plate-like particles of niobate nanosheets were investigated as a function of the aspect ratio (
) and particle volume concentration (
) by small-angle neutron scattering and small-angle X-ray scattering. The results elucidated the following three pieces of evidence: (1) the macroscopic phase separation of the dispersions into an isotropic phase and a liquid crystalline phase (LC) under the condition of (a) varying at a constant = 0.01, and of (b) varying (0.01 
0.025) at a constant = 2.5
10
. (2) the -induced phase transition of the LC phase from a nematic phase to a highly periodic layered phase upon increasing r under the condition (a). (3) the LC phase having remarkable concentration fluctuations of the particles which are totally unexpected for the conventional lyotropic molecular LC but which are anticipated to be general for the plate-like colloidal particles.
Noda, Yohei; Kumada, Takayuki; Hashimoto, Takeji; Koizumi, Satoshi
Journal of Applied Crystallography, 44(3), p.503 - 513, 2011/06
Times Cited Count：15 Percentile：77.91(Chemistry, Multidisciplinary)We measured small angle neutron scattering (SANS) for dynamically polarized block copolymer sample, one phase of which were selectively doped with radical. Dynamic nuclear polarization (DNP) caused the neutron scattering length of proton largely, as a result, the SANS intensity. By the analysis of the change of the SANS intensity, we found out the inhomogeneous distribution of the radical induced the inhomogeneous polarization (about 2% for the average polarization being 30%).
Terashima, Takaya*; Motokawa, Ryuhei; Koizumi, Satoshi*; Sawamoto, Mitsuo*; Kamigaito, Masami*; Ando, Tsuyoshi*; Hashimoto, Takeji*
Macromolecules, 43(19), p.8218 - 8232, 2010/10
Times Cited Count：42 Percentile：77.5(Polymer Science)Kumada, Takayuki; Noda, Yohei; Koizumi, Satoshi; Hashimoto, Takeji
Journal of Chemical Physics, 133(5), p.054504_1 - 054504_7, 2010/08
Times Cited Count：11 Percentile：35.27(Chemistry, Physical)We carried out time-resolved small-angle neutron scattering studies of dynamically polarized high-density polyethylene (HDPE) doped with 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) persistent free radicals. We observed an enhancement of the scattering intensity by a factor of 100 in maximum after switching a microwave frequency. The enhancement was found to be due to concentration fluctuation of TEMPO, which generates heterogeneity of polarization with the length-scale of about 100 nm and scattering due to the heterogeneity. The length scale of the heterogeneity indicates that the TEMPO free radicals are localized more in non-fibrils but less in fibrils of HDPE.
Zhao, Y.; Miyamoto, Nobuyoshi*; Koizumi, Satoshi; Hashimoto, Takeji
Macromolecules, 43(6), p.2948 - 2959, 2010/04
-poly(
-isopropylacrylamide); Elucidation of specific reaction fields for quasi-living polymerization by time-resolved SANSMotokawa, Ryuhei; Koizumi, Satoshi*; Hashimoto, Takeji*; Annaka, Masahiko*; Nakahira, Takayuki*
Macromolecules, 43(2), p.752 - 764, 2010/01
Times Cited Count：18 Percentile：50.14(Polymer Science)Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi
Journal of Magnetic Resonance, 201(2), p.115 - 120, 2009/12
Times Cited Count：7 Percentile：36.49(Biochemical Research Methods)We have carried out a dynamic nuclear polarization (DNP) study of proton spins of UV-irradiated solid butanol containing phenol. By the aid of butyl free radicals produced by the photolysis, the butanol sample was dynamically polarized up to the polarization of 1.4% at 1.5 K and 1.2 T. Unlike persistent free radicals such as nitroxy and trityl free radicals commonly used for DNP, the butyl free radicals immediately decay by melting. We propose that free radicals produced by UV-photolysis are applicable to the DNP-enhanced hyperpolarized liquid-state NMR.
Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi
Physica B; Condensed Matter, 404(17), p.2637 - 2639, 2009/09
Times Cited Count：13 Percentile：50.25(Physics, Condensed Matter)We have developed dynamic nuclear polarization (DNP) system for SANS-J-II at the JRR-3 atomic research reactor at Japan Atomic Energy Agency. Our system is composed of superconducting magnet (3.3 Tesla), Gunn oscillator as a microwave source (94 GHz), and cryostat (1.2 K). We succeeded in polarizing polyethylene sample up to 0.32 and observing effects of polarization on SANS profile. We plan to use the DNP and SANS system in order to determine structure factors of multi-component systems.
Noda, Yohei; Kumada, Takayuki; Hashimoto, Takeji; Koizumi, Satoshi
Physica B; Condensed Matter, 404(17), p.2572 - 2574, 2009/09
Times Cited Count：8 Percentile：36.66(Physics, Condensed Matter)We polarized hydrogen nuclear spins of polyethylene samples, doped with organic radical (TEMPO), by use of a dynamic nuclear polarization (DNP) technique, in which the sample was irradiated by microwave (94 GHz) at 3.3 Tesla and 1.4 K. For the samples under the DNP state, we conducted small-angle scattering experiments with polarized neutrons. For the sample with low crystallinity (polarization: 32%), the shift of the incoherent scattering level was observed. For the sample with high crystallinity (polarization: 23%), the enhancement of the coherent scattering due to the crystalline structure was observed.
Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi
Nuclear Instruments and Methods in Physics Research A, 606(3), p.669 - 674, 2009/07
Times Cited Count：11 Percentile：59.85(Instruments & Instrumentation)We carried out a DNP study of high (HPE) and low (LPE) crystallinity polyethylene films, which were doped with TEMPO. The proton polarization of 32% was obtained for LPE and 23% for HPE at 3.35 T and 1.4 K. We found by ESR study that TEMPO did not incorporated into the crystalline part, and was localized only at the amorphous part. We suggest that the smaller nuclear polarization for HPE is related to the localization of TEMPO in the smaller amorphous regions.
Iwase, Hiroki; Koizumi, Satoshi; Iikura, Hiroshi; Matsubayashi, Masahito; Yamaguchi, Daisuke; Maekawa, Yasunari; Hashimoto, Takeji
Nuclear Instruments and Methods in Physics Research A, 605(1-2), p.95 - 98, 2009/06
Times Cited Count：33 Percentile：88.55(Instruments & Instrumentation)We constructed an in-situ and simultaneous observation method as a result of combination between ultra-small-angle neutron scattering and neutron imaging (radiography). With this novel technique, we are able to visualize water distribution or transportation, occurring from micro to macro length scales in a polymer electrolyte fuel cell (PEFC). At a sample position of SANS-J-II at JRR-3, we installed a neutron imaging camera in order to construct an in-situ and simultaneous observation method by USANS and neutron imaging with monochromatized cold neutrons. In addition, in order to selectively observe MEA in a running PEFC by using the in-situ and simultaneous observation method, we need to replace carbon separators which cause strong small-angle scattering as a noise. To reduce this strong background, we replaced the carbon separators with the aluminium ones. As a result, the background scattering was minimized (1/10) as compared to before.
Zhao, Y.; Tanaka, Hirokazu*; Miyamoto, Nobuyoshi*; Koizumi, Satoshi; Hashimoto, Takeji
Macromolecules, 42(5), p.1739 - 1748, 2009/04
Times Cited Count：15 Percentile：45.74(Polymer Science)Yamaguchi, Daisuke; Mayama, Hiroyuki*; Koizumi, Satoshi; Tsujii, Kaoru*; Hashimoto, Takeji
European Physical Journal B, 63(2), p.153 - 163, 2008/05
The fractal dimensions of specific porous silica materials were investigated by a wide-q observation using ultra-small-angle neutron scattering technique. In order to control the fractal dimension of porous silica material, flaky particles made of alkylletene dimer (AKD) were employed as moulds and silica matrix was formed by sol-gel process. After the solidification of the silica matrix, the original AKD moulds were completely burnt away at high temperature (ca. 930K) and became pores having a particular fractal dimension. The fractal dimension of the pores was changeable by the compression of the AKD mould at different ratio during the sample preparation. We found that the fractal structure obtained in this study was distinctly different from those of ordinary silica aerogels.
Yamaguchi, Daisuke; Mayama, Hiroyuki*; Koizumi, Satoshi; Tsujii, Kaoru*; Hashimoto, Takeji
European Physical Journal B, 63(2), p.153 - 163, 2008/05
Times Cited Count：12 Percentile：48.4(Physics, Condensed Matter)The unique structure of a set of self-assembled porous silica materials was characterized through a combined small-angle scattering (CSAS) method using small- and ultra-small angle neutron scattering as well as small-angle X-ray scattering. The porous silica specimens investigated were prepared by a sol-gel method under the presence of alkylketene dimer (AKD) template particles and through calcination, which leads to the development of porous silica having a mass-fractal structure over length scales from 10nm to 10
m. Furthermore, the specimens posses a hierarchical structure, which consist of a fractal porous structure, and also contain primary silica particles less than 10 nm in size, which form a continuous silica matrix. To characterize these complex structures, observation over a broad range of length scales is indispensable. We propose a CSAS technique that serves this purpose well.
Koizumi, Satoshi; Zhao, Y.; Tomita, Yoko*; Kondo, Tetsuo*; Iwase, Hiroki; Yamaguchi, Daisuke; Hashimoto, Takeji
European Physical Journal E, 26(1-2), p.137 - 142, 2008/05
Times Cited Count：55 Percentile：86.02(Chemistry, Physical)no abstracts in English
Tanaka, Hirokazu*; Hashimoto, Takeji; Koizumi, Satoshi; Ito, Hideaki*; Naka, Kensuke*; Chujo, Yoshiki*
Macromolecules, 41(5), p.1815 - 1824, 2008/03
Times Cited Count：8 Percentile：26.86(Polymer Science)We have investigated the self-assembly formed by palladium acetate (Pd(OAc)
) and polyamidoamine dendrimers (GN-NH) in a mixed solvent of methanol and N, N-dimethylformamide. We aim to explore effects of the generation number (GN) and concentration of the dendrimers, [GN-NH], on the self-assembly of the dendrimers (defined hereafter as "templates") and the Pd nanoparticles inside the templates in order to clarify physical factors controlling the self-assembling mechanisms. We found that the templates are formed only when [GN-NH] falls below a critical value and thereby a sufficient amount of Pd(OAc) exists as the binders between the dendrimers. Otherwise dendrimers are molecularly dispersed in solution.
Koga, Tadanori*; Hashimoto, Takeji; Takenaka, Mikihito*; Aizawa, Kazuya; Amino, Naoya*; Nakamura, Masao*; Yamaguchi, Daisuke; Koizumi, Satoshi
Macromolecules, 41(2), p.453 - 464, 2008/01
Times Cited Count：112 Percentile：95.04(Polymer Science)Using a combined ultra-small-angle and small-angle scattering method of neutrons and X-rays, we investigated hierarchical structures of carbon black (CB) highly loaded in polyisoprene (PI) and poly-(styrene-random-butadiene) copolymer (SBR) under mechanical field (defined respectively as CB/PI and CB/SBR) as well as in toluene under a sonic field (defined as CB/toluene). Comparison of the scattering profiles from CB/PI and CB/SBR with CB/toluene clarified that (1) the smallest structure elements of CB in PI and SBR were composed of the several unbreakable units bounded together by polymer chains (defined as "dispersible units") and (2) sizes and shapes of the dispersible units depended on the polymer matrix. (3) Moreover, the enlarged size of the dispersible unit in PI was found to enlarge the upper cutoff length of the mass-fractal structure in PI, while the mass-fractal dimensions themselves remained unchanged between PI and SBR.
Motokawa, Ryuhei; Iida, You*; Zhao, Y.; Hashimoto, Takeji; Koizumi, Satoshi
Polymer Journal, 39(12), p.1312 - 1318, 2007/12
Times Cited Count：16 Percentile：45.95(Polymer Science)By utilizing a biconcave refractive neutron lens (MgF), we constructed a focusing ultra-small-angle neutron scattering (USANS) spectrometer (SANS-J-II) at research reactor JRR3, Tokai Japan. SANS-J-II can successfully reach to 
=0.0003 
, where [= 4
sin()/
] is the magnitude of scattering vector given by wavelength and scattering angle 2, and simultaneously cover conventional SANS region up to = 0.004 by using 5-inch size & high resolution position sensitive area photomultiplier with scintillator (ZnS). Focusing USANS, thus realized, plays an important role to investigate the time-evolution of hierarchically ordered structures in the living radical polymerization solution, preparing poly (methyl methacrylate)- -polystyrene (PMMA-
-PS). In the reaction process to synthesize PS block chains from the end of PMMA block chain, we found the interplay between macro and microdomain structures as follows. Small-angle scattering at 
0.001 determined time-evolving microdomain structures; as the polymerization proceeds, (1) first by order-disorder transition, a lamellar microdomain appears and (2) second by order-order transitions, the morphologies of microdomains change to PS cylinder and successively to PS sphere. Ultra-small-angle scattering at 
0.001 , exhibits power law scattering (
) due to macrophase separation between PMMA--PS and PS homopolymer, appeared as by product. The exponent 
varies from 4 to 2, reflecting a grain boundary of macrodomain rich-in PMMA--PS; when a lamellar microdomain appears, Porod law gives = 4, whereas when cylinder and sphere appear, = 2, due to inhomogeniety of the microdomain spatial distribution.
Tanaka, Hirokazu*; Koizumi, Satoshi; Hashimoto, Takeji; Kurosaki, Kazuhiro*; Kobayashi, Shiro*
Macromolecules, 40(17), p.6304 - 6315, 2007/08
Times Cited Count：30 Percentile：65.02(Polymer Science)We have investigated the self-assembling process of cellulose artificially synthesized via enzymatic polymerization as one of general problems of non-equilibrium phenomenon and pattern formation. The chemical reaction and the self-assembling process were explored at real time and in-situ by a combined small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), ultra-SANS and ultra-SAXS method, together with wide-angle X-ray diffraction and field-emission scanning electron microscopy. The results revealed for the first time the following pieces of new evidence: (1) The enzymes (cellulase) as a catalyst aggregate themselves into associations; (2) Cellulose molecules created at each active site of enzymes associate themselves around the enzyme associations into cellulose aggregates having surface fractal dimensions Ds, increasing from 2 to 2.3 with reaction time. (3) The fractal structure formed at the end of the reaction extends over a surprisingly wide length scale ranging from 30 nm to 30 m (3 orders of magnitude).
