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Journal Articles

Hierarchically self-organized dissipative structures of filler particles in poly(styrene-$$ran$$-butadiene) rubbers

Yamaguchi, Daisuke; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*; Noda, Yohei*; Koizumi, Satoshi*; Hashimoto, Takeji*

Macromolecules, 50(19), p.7739 - 7759, 2017/10

 Times Cited Count:8 Percentile:37.66(Polymer Science)

We elucidated the spatial distribution of filler particles in cross-linked poly(styrene-$$ran$$-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.

Journal Articles

Order-disorder transition of nanocomposites; Polystyrene-$$block$$-poly(methyl methacrylate) with Pd nanoparticles

Zhao, Y.; Saijo, Kenji*; Hashimoto, Takeji

Macromolecules, 46(3), p.957 - 970, 2013/02

 Times Cited Count:7 Percentile:25.81(Polymer Science)

Journal Articles

Aspect-ratio-dependent phase transitions and concentration fluctuations in aqueous colloidal dispersions of charged platelike particles

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:19 Percentile:75.27(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 ($$r_{rm asp}$$) and particle volume concentration ($$theta$$$$_{rm P}$$) 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 $$r_{rm asp}$$ at a constant $$theta$$$$_{rm P}$$ = 0.01, and of (b) varying $$theta$$$$_{rm P}$$ (0.01 $$leq$$ $$theta$$$$_{rm P}$$ $$leq$$ 0.025) at a constant $$r_{rm asp}$$ = 2.5$$times$$10$$^{-3}$$. (2) the $$r_{rm asp}$$-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.

Journal Articles

Inhomogeneous dynamic nuclear polarization of protons in a lamella-forming diblock copolymer investigated by a small-angle neutron scattering method

Noda, Yohei; Kumada, Takayuki; Hashimoto, Takeji; Koizumi, Satoshi

Journal of Applied Crystallography, 44(3), p.503 - 513, 2011/06

 Times Cited Count:13 Percentile:76.86(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%).

Journal Articles

In situ and time-resolved small-angle neutron scattering observation of star polymer formation via arm-linking reaction in ruthenium-catalyzed living radical polymerization

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:39 Percentile:77.82(Polymer Science)

Journal Articles

Mesoscale spatial distribution of electron spins studied by time-resolved small-angle and ultrasmall-angle neutron scattering with dynamic nuclear polarization; A Case of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) doped in high-density polyethylene

Kumada, Takayuki; Noda, Yohei; Koizumi, Satoshi; Hashimoto, Takeji

Journal of Chemical Physics, 133(5), p.054504_1 - 054504_7, 2010/08

 Times Cited Count:9 Percentile:31.04(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.

Journal Articles

Soap-free emulsion polymerization of poly(ethylene glycol)-${it block}$-poly($$N$$-isopropylacrylamide); Elucidation of specific reaction fields for quasi-living polymerization by time-resolved SANS

Motokawa, Ryuhei; Koizumi, Satoshi*; Hashimoto, Takeji*; Annaka, Masahiko*; Nakahira, Takayuki*

Macromolecules, 43(2), p.752 - 764, 2010/01

 Times Cited Count:15 Percentile:46.68(Polymer Science)

Journal Articles

Dynamic nuclear polarization study of UV-irradiated butanol for hyperpolarized liquid NMR

Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi

Journal of Magnetic Resonance, 201(2), p.115 - 120, 2009/12

 Times Cited Count:6 Percentile:34.07(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.

Journal Articles

Dynamic nuclear polarization system for the SANS-J-II spectrometer at JAEA

Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi

Physica B; Condensed Matter, 404(17), p.2637 - 2639, 2009/09

 Times Cited Count:11 Percentile:46.93(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.

Journal Articles

Small-angle neutron scattering study of dynamically polarized polyethylenes

Noda, Yohei; Kumada, Takayuki; Hashimoto, Takeji; Koizumi, Satoshi

Physica B; Condensed Matter, 404(17), p.2572 - 2574, 2009/09

 Times Cited Count:8 Percentile:38.1(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.

Journal Articles

Dynamic nuclear polarization of high- and low-crystallinity polyethylenes

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:10 Percentile:59.1(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.

Journal Articles

A Combined method of small-angle neutron scattering and neutron radiography to visualize water in an operating fuel cell over a wide length scale from nano to millimeter

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:31 Percentile:89.51(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.

Journal Articles

Super ODS steels R&D for fuel cladding of next generation nuclear systems, 2; Effect of minor alloying elements

Onuki, Somei*; Hashimoto, Naoyuki*; Ukai, Shigeharu*; Kimura, Akihiko*; Inoue, Masaki; Kaito, Takeji; Fujisawa, Toshiharu*; Okuda, Takanari*; Abe, Fujio*

Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9306_1 - 9306_5, 2009/05

For development of advanced ferritic ODS steels including high concentration of Cr and Al, the effect of minor alloying elements on fine dispersion of oxide particle was investigated. Microstructural analysis for Fe-16Cr-4Al-mY$$_{2}$$O$$_{3}$$-nZr or mHf due to TEM indicated that 0.3Zr or 0.6Hf are the optimum concentration. The mechanism of nano-sized oxide formation was also discussed.

Journal Articles

Super ODS steels R&D for fuel cladding of next generation nuclear systems, 9; Damage structure evolution under electron-irradiation

Onuki, Somei*; Hashimoto, Naoyuki*; Ukai, Shigeharu*; Kimura, Akihiko*; Inoue, Masaki; Kaito, Takeji; Fujisawa, Toshiharu*; Okuda, Takanari*; Abe, Fujio*

Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9307_1 - 9307_4, 2009/05

The aim of this study is to survey microstructural properties and irradiation response of advanced high Cr and Al ODS steels. The effects of minor element addition and heat-treatment are also investigated. In these steels, black dots-like dislocation loops were formed around oxide particles during electron irradiation, and then the behavior depended on the type of additional elements, but the irradiation resistance was confirmed generally. The irradiation response was not sensitive as the heat-treatment, but the minor element addition (Zr and Hf) showed an intensive suppressing the loop growth. The results suggest that a large number of oxides enhanced the mutual recombination of the irradiation-induced point defects, especially at their surface.

Journal Articles

Combined SANS, SEC, NMR, and UV-Vis studies of simultaneous living anionic copolymerization process; Simultaneous elucidation of propagating living chains at three different length scales

Zhao, Y.; Tanaka, Hirokazu*; Miyamoto, Nobuyoshi*; Koizumi, Satoshi; Hashimoto, Takeji

Macromolecules, 42(5), p.1739 - 1748, 2009/04

 Times Cited Count:13 Percentile:43.27(Polymer Science)

Journal Articles

Frustrating the lamellar ordering transition of polystyrene-${it block}$-polyisoprene with a C$$_{60}$$ additive

Zhao, Y.; Hashimoto, Takeji; Douglas, J.*

Journal of Chemical Physics, 130(12), p.124901_1 - 124901_6, 2009/03

 Times Cited Count:6 Percentile:20.19(Chemistry, Physical)

Journal Articles

SAXS analysis of the order-disorder transition and the interaction parameter of polystyrene-${it block}$-poly(methyl methacrylate)

Zhao, Y.; Sivaniah, E.*; Hashimoto, Takeji

Macromolecules, 41(24), p.9948 - 9951, 2008/12

 Times Cited Count:115 Percentile:95.92(Polymer Science)

Journal Articles

Morphological and scattering studies of binary mixtures of block copolymers; Cosurfactant effects observed in the parameter space of temperature, blend composition, and molecular weight ratio

Fran$c{c}$ois, C.*; Yamaguchi, Daisuke; Hashimoto, Takeji

Macromolecules, 41(13), p.4828 - 4837, 2008/07

 Times Cited Count:22 Percentile:58.16(Polymer Science)

Thermoreversible order-order transitions between various morphologies occurring on binary mixtures of diblock copolymers were investigated by using small-angle X-ray scattering. The complex morphological behaviors observed here can be understood on the basis of two key features of the binary blends: the co-surfactant effect and the possibility for the chemical junctions of the shorter diblock to migrate away from the interface as segregation power decreases. As a summary of this series of studies, a three-dimensional phase diagram was constructed in the parameter space of overall volume fraction of polystyrene block in the mixture, the ratio of the degree of polymerization of long asymmetric diblock chain to that of short symmetric diblock chain and temperature. Such a phase diagram illustrates that the cosurfactant effect opens perspectives in tailoring morphologies of self-assembled, nano-structured materials.

Journal Articles

Investigation of self-assembled fractal porous-silica over a wide range of length scales using a combined small-angle scattering method

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.

163 (Records 1-20 displayed on this page)