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Journal Articles

Mesoporous silica particles as topologically crosslinking fillers for poly($$N$$-isopropylacrylamide) hydrogels

Miyamoto, Nobuyoshi*; Shimasaki, Kotaro*; Yamamoto, Kosuke*; Shintate, Morio*; Kamachi, Yuichiro*; Bastakoti, B. P.*; Suzuki, Norihiro*; Motokawa, Ryuhei; Yamauchi, Yusuke*

Chemistry; A European Journal, 20(46), p.14955 - 14958, 2014/11

 Times Cited Count:17 Percentile:50.63(Chemistry, Multidisciplinary)

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

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

Hierarchical structure of niobate nanosheets in aqueous solution

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Nakato, Teruyuki*; Hashimoto, Takeji

Journal of Applied Crystallography, 40(s1), p.s101 - s105, 2007/04

 Times Cited Count:20 Percentile:85.6(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Living anionic polymerization of methyl methacrylate controlled by metal-free phosphazene catalyst as observed by small-angle neutron scattering, gel-permeation chromatography and UV-visible spectroscopy

Miyamoto, Nobuyoshi; Inoue, Yoshihisa*; Koizumi, Satoshi; Hashimoto, Takeji

Journal of Applied Crystallography, 40(s1), p.s568 - s572, 2007/04

 Times Cited Count:5 Percentile:54.67(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Aggregation behavior of polyisoprene chain ends during living anionic polymerization as investigated by time-resolved small-angle neutron scatting

Miyamoto, Nobuyoshi; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Hashimoto, Takeji; Koizumi, Satoshi

Physica B; Condensed Matter, 385-386(1), p.752 - 755, 2006/11

 Times Cited Count:4 Percentile:23.48(Physics, Condensed Matter)

The living anionic polymerization processes of isoprene and styrene in benzene-$textit{d}$ $$_{6}$$ initiated by $textit{sec}$-butyl lithium were studied by in-situ small-angle neutron scattering (SANS) and time-resolved molecular weight ($textit{Mn}$) measurement by gel permeation chromatography (GPC). In the course of the polymerization of isoprene ($textit{e.g.}$ $textit{Mn}$ = 5300 g mol$$^{-1}$$), the small angle scattering increased with the reaction time $textit{t}$. The molecular weight and its time-change, determined by GPC, is crucial to quantitatively analyze time-resolved SANS measurements; we were able to determine association number $textit{f}$ uniquely as a function of $textit{t}$. Upon termination of the living polymerization, SANS profile greatly changed: the scattering intensity in the intermediate $textit{q}$-region (0.2 $$leq$$ $textit{q}$ $$leq$$ 1.0 nm$$^{-1}$$) remarkably decreased, indicating disaggregation of the living ends upon the termination. Also, strong upturn in the low-q region appeared (q $$leq$$ 0.1 nm$$^{-1}$$) due to the generation of colloidal LiOH or LiO(C$$_{2}$$H$$_{5}$$), which are insoluble in benzene. Detailed data and analyses of isoprene and styrene systems will be given in the presentation.

Journal Articles

In situ and real-time small-angle neutron scattering studies of living anionic polymerization process and polymerization-induced self-assembly of block copolymers

Tanaka, Hirokazu; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Hashimoto, Takeji

Physica B; Condensed Matter, 385-386(1), p.742 - 744, 2006/11

 Times Cited Count:16 Percentile:59.27(Physics, Condensed Matter)

Polystyrene-block-polyisoprene were synthesized via living anionic polymerization. We have performed in-situ and real-time SANS, GPC, and UV-vis spectroscopy of the polymerization process in order to reveal the structure formation process of the block copolymers, especially the associated structures. From GPC and UV-vs spectroscopy. It is found that isoprene monomers are preferentially polymerized, and after that, styrene monomers are to be polymerized. It is also found from SANS measurements, that living polymers in the reaction solution formed the associated structures during the polymerization process. Moerover, it is also strongly suggested that in the earlier stage of polymerization, living polymers are mainly composed of polyisoprene with association number of 4, and once styrene monomers are polymerized, the association number drastically begins to decrease from 4 to 2.

Journal Articles

Recent ITER physics R&D expert group activities

Ogawa, Yuichi*; Takizuka, Tomonori; Miura, Yukitoshi; Toi, Kazuo*; Fukuda, Takeshi; Wakatani, Masahiro*; Ide, Shunsuke; Takase, Yuichi*; Tobita, Kenji; Fukuyama, Atsushi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 77(10), p.1042 - 1048, 2001/10

no abstracts in English

Oral presentation

Small angle neutron scattering observation of liquid crystalline sol of niobate nanosheets

Miyamoto, Nobuyoshi; Yamaguchi, Daisuke; Nakato, Teruyuki*; Koizumi, Satoshi; Hashimoto, Takeji

no journal, , 

The structure of liquid crystalline sols of niobate nanosheets was observed by USANS, SANS, and USAXS as the function of the average lateral size L and the volume fraction $$phi$$ of the nanosheets. The nanosheets sols were obtained by a reaction of K$$_{4}$$Nb$$_{6}$$O$$_{17}$$ crystals with propylammonium followed by washing with water. The sol was ultrasonicated for 10-180 min and diluted to yield the series of the samples with different L and $$phi$$. At q$$>$$ 0.1, the peaks due to the lamellar structure of the liquid crystal were observed in the scattering curves. The basal spacing was ca. 40 nm, independent of L, at $$phi$$ = 3.6 vol % and it decreased with decreasing $$phi$$. The scattering curves at 0.01 $$<$$ q $$<$$ 0.1 depended largely on L, or the form factor of the nanosheets. At q $$<$$ 0.01 nm$$^{-1}$$, the power law of q$$^{-2.5}$$ was observed independent of L, indicating the presence of the liquid crystalline domains with mass fractal structure.

Oral presentation

Observation and analysis of the niobate nanosheet solution

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Nakato, Teruyuki*; Hashimoto, Takeji

no journal, , 

The exfoliated K$$_{4}$$Nb$$_{6}$$O$$_{17}$$ nanosheets in the aqueous solutions were observed by (ultra-) small-angle neutron and X-ray scattering (SANS, USANS and USAXS). A comprehensive measurement revealed the assembled structure of nanosheets in wide range of q, from 3$$times$$10$$^{-4}$$ nm$$^{-1}$$ to 1 nm$$^{-1}$$, where q is the magnitude of scattering vector. The details of liquid crystalline structure formed by [Nb$$_{6}$$O$$_{17}$$]$$^{4-}$$ nanosheets, which was reflected on the scattering at higher q region ($$>$$3$$times$$10$$^{-2}$$ (nm$$^{-1}$$)), largely depend on the nanosheet lateral dimension or its volume fraction. On the other hand, at lower q region ($$<$$1$$times$$10$$^{-2}$$ (nm$$^{-1}$$)), the scattering profile shows a power law scattering of which index is -2.5 regardless of the nanosheet lateral dimension or its volume fraction, suggesting that at large scale nanosheets take similar mass fractal distribution.

Oral presentation

In-situ observation of living anionic polymerization process by small-angle neutron scatterin

Miyamoto, Nobuyoshi; Tanaka, Hirokazu*; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Hashimoto, Takeji; Koizumi, Satoshi

no journal, , 

The living anionic polymerization processes of polyisoprene, polystyrene, and polystyrene-block-polyisoprene were studied by in-situ small-angle neutron scattering (SANS) in combination with gel permeation chromatography and uv-visible spectroscopy. The polymerization reactions were carried out in benzene-d6 with sec-butyllithium as the initiator. The SANS intensity largely decreased upon termination of the living ends, indicating the presence of ionic aggregates during polymerization. The time-courses of the aggregation number f in the aggregates during the polymerizations were quantitatively estimated by analyzing the time-resolved SANS data on the basis of the model of star-polymer. In isoprene systems, the aggregation number decreased from ca. 10 to 4 with increasing molecular weight.

Oral presentation

Structure analysis of liquid crystalline nanosheet of niobate, 1

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Nakato, Teruyuki*; Hashimoto, Takeji

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

In-situ observation of living anionic polymerization process by simultaneous measurements of small angle neutron scattering and UV-vis spectroscopy

Miyamoto, Nobuyoshi; Inoue, Yoshihisa*; Koizumi, Satoshi; Hashimoto, Takeji

no journal, , 

no abstracts in English

Oral presentation

Hierarchical structure of nanosheet colloid observed by ultra-small-angle neutron scattering

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Nakato, Teruyuki*; Mayama, Hiroyuki*; Tsujii, Kaoru*; Hashimoto, Takeji

no journal, , 

no abstracts in English

Oral presentation

In-situ and time-resolved observation of living anionic polymerization process

Miyamoto, Nobuyoshi; Koizumi, Satoshi; Hashimoto, Takeji

no journal, , 

no abstracts in English

Oral presentation

In situ and real-time observation of living anionic polymerization process and polymerization-induced self-assembly of polyisoprene-b-polystyrene-d8

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

no journal, , 

In-situ and real-time observation of simultaneous living anionic polymerization process of isoprene (I) and styrene-d8 (S) in benzene-d6 as a solvent with sec-buthyllithium as an initiator into polyisoprene-block-polystyrene-d8 and the polymerization-induced self-assembling structures was carried out by a combination of UV-vis spectroscopy, gel permission chromatography (GPC), nuclear magnetic resonance (NMR) and Small-angle Neutron Scattering (SANS) experiments. The results revealed three time regions with time. In region 1, Only PI blocks were growing. In region 2, PS segments were formed and tapered structures were observed. In region 3, PS blocks were growing rapidly, and polymerization-induced microphase separation was observed.

Oral presentation

Observation of the self-assembled structure of the two-dimensional particles system

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi*; Koizumi, Satoshi; Hashimoto, Takeji; Nakato, Teruyuki*; Mayama, Hiroyuki*; Tsujii, Kaoru*

no journal, , 

The hierarchical structures composed of two-dimensional particles were observed via ultra-small-angle scattering method. We have investigated two systems: (1) exfoliated K$$_{4}$$Nb$$_{6}$$O$$_{17}$$ nanosheet colloidal dispersion, (2) porous silica fabricated from alkylketene dimer template. Although the physical and chemical structures and properties are largely different in these two systems, a similar point to them is regarded as below. The thickness of the constituent particles is ranging from a few nanometers to several tens of nanometers. Various fractal-like power-law scattering were obtained in the ultra-small angle scattering region reflecting the difference in the self-assembly of the particles.

Oral presentation

In-situ and real-time observation of simultaneous living anionic copolymerization of isoprene and styrene by SANS, SEC,UV-vis, and NMR

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

no journal, , 

We explored a simultaneous living anionic copolymerization process of isoprene and styrene monomers in benzene as a nonpolar solvent and polymerization-induced self-assembly by means of a combined small-angle neutron scattering, SEC and UV-vis spectroscopy.

33 (Records 1-20 displayed on this page)