Faculty Profiles - NAKANISHI Kazuki

Papers - NAKANISHI Kazuki

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Size exclusion chromatography of standard polystyrenes with a wide range of molecular weight up to 7.45 x 10(6) on monolithic silica capillary columns Reviewed Open Access

Koichi Ute, Saori Yoshida, Tatsuki Kitayama, Takeshi Bamba, Kazuo Harada, Eiichiro Fukusaki, Akio Kobayashi, Norio Ishizuka, Hiroyoshi Minakuchi, Kazuki Nakanishi

POLYMER JOURNAL Vol. 38 ( 11 ) page： 1194 - 1197 2006

Porous methylsiloxane gel thick film for millimeter-wave antenna substrate prepared by gap filling method Reviewed

Takeharu Tanaka, Nobuyuki Kawakami, Takayuki Hirano, Yoshito Fukumoto, Tetsuo Suzuki, Kazuyoshi Kanamori, Kazuki Nakanishi

MATERIAL AND DEVICES FOR SMART SYSTEMS II Vol. 888 page： 251 - + 2006

Language：English Publishing type：Research paper (international conference proceedings) Publisher：MATERIALS RESEARCH SOC

A novel process to fabricate a thick silica gel film on an aluminum substrate, named the gap filling method", has been developed. The process is based on a sol-gel method accompanied by phase separation in a submillimeter thick space defined by two facing substrates. Dielectric thick film integrated on a metal ground plate is successfully formed by using a SiO2 coated aluminum substrate and a cap plate covered with an amorphous carbon thin film, which control the hydrophilicity and the hydrophobicity of the plates, respectively. A thin continuous layer of less than 0. fn thick is formed at the interface between the porous film and the cap plate, which gives the film a smooth surface preferable for patterning metal circuits of an antenna. The observed dielectric constants (epsilon r) at 60 GHz measured by the Fabry-Perot resonator method are in the range between 1.4 and 1.6. Methyl groups homogeneously distributed in the siloxane network give a hydrophobic siloxane gel film, thus the obtained films have enough environmental stability. These results show that the gap filling method is applicable to the preparation of the porous thick film that is needed for antenna applications.

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Preparation of novel macroporous polymer monoliths using polymerization-induced phase separation Reviewed

K. Kanamori, K. Nakanishi

Polymer Preprints, Japan Vol. 55 ( 1 ) page： 929- 2006

Control of light scattering in organic-inorganic hybrid macroporous monoliths

Takayuki Hirao, Shunsuke Murai, Koji Fujita, Kazuki Nakanishi, Kazuyuki Hirao

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy Vol. 52 ( 10 ) page： 781 - 785 2005.10

Language：Japanese Publishing type：Research paper (scientific journal)

The tuning of light scattering strength has been demonstrated for organic-inorganic hybrid monoliths with well-defined through-pores in micrometer range. Macroporous gels having interconnected pores and skeletons are obtained in a system containing methyltrimethoxysilane, water, nitric acid, and methanol using an alkoxy-derived sol-gel method combined with the phase separation. The sizes of pores and skeletons can be controlled by varying molar ratios of water and methanol in the starting compositions which mostly affect the onset of polymerization-induced phase separation in the system. The mercury porosimetry shows that the resultant gels have a sharp pore size distribution, and the average pore diameter increases with increasing the amount of water and methanol. The coherent backscattering measured for the gels formed in between two slide glasses reveals that the transport mean free path of light decreases with decreasing the sizes of pores and skeletons. Pore size dependence of the scattering strength can be qualitatively explained by a Mie scattering calculation using a model in which spherical pores are randomly distributed in methylsiloxane matrix. The results indicate that the scattering strength can be tuned by controlling the sizes of the pores.

DOI： 10.2497/jjspm.52.781

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Tailoring spontaneous pillar structure using phase-separating organosiloxane sol-gel systems in micro-fabricated grooves Reviewed

K Kanamori, K Nakanishi, K Hirao, H Jinnai

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY Vol. 35 ( 3 ) page： 183 - 191 2005.9

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

A sharp transition to pillar structure has been observed in simple sol-gel systems accompanying phase separation inside rectangular-sectioned open grooves which were fabricated on a silica glass chip. The structural variation was investigated using two contrastive systems; one with a rapid sol-gel reaction and the other with a sluggish reaction. In the slower system, transition from web-like bicontinuous structure to pillar structure, we call it as "web-to-pillar transition", occurred when the bulk characteristic length Lambda(m) m exceeded the width of the groove D. On the other hand, the transition did not occur in the same condition in the faster system; it occurred when Lambda(m) became much longer than D. A consistent formation mechanism model was also proposed using a relation between interfacial curvatures and pressure.A sharp transition to pillar structure has been observed in simple sol-gel systems accompanying phase separation inside rectangular-sectioned open grooves which were fabricated on a silica glass chip. The structural variation was investigated using two contrastive systems; one with a rapid sol-gel reaction and the other with a sluggish reaction. In the slower system, transition from web-like bicontinuous structure to pillar structure, we call it as "web-to-pillar transition", occurred when the bulk characteristic length Lambda(m) exceeded the width of the groove D. On the other hand, the transition did not occur in the same condition in the faster system; it occurred when Lambda(m) became much longer than D. A consistent formation mechanism model was also proposed using a relation between interfacial curvatures and pressure.

DOI： 10.1007/s10971-005-4166-z

An application of silica-based monolithic membrane emulsification technique for easy and efficient preparation of uniformly sized polymer particles Reviewed

K Hosoya, M Bendo, N Tanaka, Y Watabe, T Ikegami, H Minakuchi, K Nakanishi

MACROMOLECULAR MATERIALS AND ENGINEERING Vol. 290 ( 8 ) page： 753 - 758 2005.8

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Uniformly sized polymer particles were prepared by an emulsification and polymerization technique utilizing a silica monolithic membrane, namely the "silica monolithic membrane emulsification technique". In this paper, we utilized silica monolithic membrane as a device for the preparation of uniformly sized polymer particles. A mixture of monomers, diluents and oil-soluble initiator was emulsified into a continuous medium through the silica monolithic membrane and polymerized. The particles obtained had a higher size uniformity than that of particles prepared by previously reported membrane emulsification techniques, such as the Shirasu Porous Glass (SPG) emulsification technique. Through the silica monolithic membrane emulsification technique, we could prepare particles having availability as a possible packing material for solid-phase extraction (SPE) and high performance liquid chromatography (HPLC).

DOI： 10.1002/mame.200500006

Silica monolithic membrane as separation medium - Summable property of different membranes for high-performance liquid chromatographic separation Reviewed

K Hosoya, T Ogata, Y Watabe, T Kubo, T Ikegami, N Tanaka, H Minakuchi, K Nakanishi

JOURNAL OF CHROMATOGRAPHY A Vol. 1073 ( 1-2 ) page： 123 - 126 2005.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We studied an applicability of a silica monolithic membrane as separation medium for high-performance liquid chromatography (HPLC). We prepared porous monolithic silica membranes having a three-dimensional network structure to cut and shape into a membrane separation medium. We evaluated chromatographic properties of a variety of solutes using a column containing the membranes with HPLC to elucidate summable property of the membrane separation media. In addition, we made brief study on separation of HbA1c in whole blood with the "stacked" membranes having different surface characteristics in one column, which is a membrane column. We confirmed that the membrane column was able to separate HbA1c from other matrix in whole blood to some extent, and it also had an excellent ability for hydrophobic and ion exchange adsorption. &COPY; 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2004.09.042

Monolithic periodic mesoporous silica with well-defined macropores Reviewed

T Amatani, K Nakanishi, K Hirao, T Kodaira

CHEMISTRY OF MATERIALS Vol. 17 ( 8 ) page： 2114 - 2119 2005.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Monolithic pure silica gels with hierarchical macro-mesoporous structure have been synthesized via a spontaneous sol-gel process from silicon alkoxide using a structure-directing agent and a micelle-swelling agent. A monolithic body with well-defined co-continuous macropores is a result of concurrent phase separation and sol-gel transition induced by the polymerization reaction, whereas the mesopores are templated by the cooperative self-assembly of inorganic species, a structure-directing agent, and a micelle-swelling agent. These bimodal pore systems are formed spontaneously in a closed condition at a constant temperature. The following removal of surfactants by heat-treatment gives silica gels with hierarchical and fully accessible pores in discrete size ranges of micrometers and nanometers. The highly ordered 2D-hexagonal arrays of mesopores have been confirmed by X-ray diffraction measurements and FE-SEM observations. Furthermore, by further additions of the micelle-swelling agent, the mesostructural transition from well-ordered 2D-hexagonal arrays to mesostructured cellular foams (MCF) has been induced accompanied by minor modifications of the micrometer-range structure.

DOI： 10.1021/cm048091c

High-performance frontal analysis of the binding of thyroxine enantiomers to human serum albumin Reviewed

Kimura T, Nakanishi K, Nakagawa T, Shibukawa A, Matsuzaki K

PHARMACEUTICAL RESEARCH Vol. 22 ( 4 ) page： 667 - 675 2005.4

Recent advances in the design of monolithic silica columns: From small to big dimensions. Reviewed

K Cabrera, A Kraus, H Minakuchi, K Nakanishi

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 229 page： U144 - U144 2005.3

Insight on structural change in sol-gel-derived silica gel with aging under basic conditions for mesopore control Reviewed

R Takahashi, K Nakanishi, N Soga

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY Vol. 33 ( 2 ) page： 159 - 167 2005.2

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Structural rearrangement of sol-gel-derived silica gel by aging under basic conditions was investigated using small angle X-ray scattering (SAXS) and Si-29 nuclear magnetic resonance (NMR). A wet silica gel prepared under acidic conditions had a fractal nature, and many unreacted silanols remained on the surface. During aging of the gel in ammonia solution, additional Si-O-Si bonds rapidly formed, whereas the change in mesoscale structure gradually proceeded. This result was compared with that of simulation modeling the Ostwald ripening, i.e. dissolution from positive curvature and reprecipitation on negative curvature. In the simulation, structural change in a cluster from fractal nature to particle aggregates was well visualized in 2-dimmensional square lattice. Both scattering profiles calculated from the model clusters and the change in average coordination number of monomers in the cluster well agreed with the experimental SAXS and NMR results, respectively. This agreement strongly ensures us that structural change by aging under basic conditions proceeds through the Ostwald ripening. The mesopore size as well as mesopore volume in calcined silica gel is determined by the shrinkage degree during drying and calcination. The sample aged in basic solution restrains the shrinkage because of the growth of particulate structure, and retains large size and volume of pores.

DOI： 10.1007/s10971-005-5610-9

Titania-coated monolithic silica as separation medium for high performance liquid chromatography of phosphorus-containing compounds Reviewed

S Miyazaki, MY Miah, K Morisato, Y Shintani, T Kuroha, K Nakanishi

JOURNAL OF SEPARATION SCIENCE Vol. 28 ( 1 ) page： 39 - 44 2005.1

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A method of preparing titania-coated monolithic silica stationary phase has been developed to achieve liquid chromatographic separation of phosphorus-containing compounds, which have recently been attracting increasing attention in biochemical research. The titania-coated silica columns exhibited efficient separation with low pressure drop, which is a typical feature of monolithic structures, and also possessed phospho-selectivity, which is a unique property of the titania surface. The material characteristics of titania-coated monolithic silica were examined, and then resin-clad columns were applied to the HPLC analysis of phosphorylated compounds. Highly efficient separation of phosphorylated substances indicated that the novel titania-coated monolithic silica column will find applications as a useful tool in the field of biochemistry, especially in post-genomic analyses.

DOI： 10.1002/jssc.200401932

Formation of photonic structures inSM(2+)-doped aluminosilicate glasses through phase separation Reviewed

K Fujita, S Murai, K Nakanishi, K Hirao

Micromachining Technology for Micro-Optics and Nano-Optics III Vol. 5720 page： 261 - 268 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：SPIE-INT SOC OPTICAL ENGINEERING

Sm2+-doped Al2O3-SiO2 glasses with three-dimensionally interconnected macroporous morphology have been prepared via the alkoxy,-derived sol-gel process containing poly (ethylene oxide) and SmCl3 center dot 6H(2)O. The macroporous morphology . is obtained by cconcurrently inducing the phase separation and sol-gel transition. Using a visible laser with the wavelength of 488 nm, the valence State Of Sm2+ has been manipulated spatially, When the photoionization Of Sm2+ is combined with multiple light scattering in the porous glasses, holes are burned in wave-vector domain. The hole profile can be controlled by adjusting the macroporous morphology.

DOI： 10.1117/12.590712

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Topical application of ionic polymers affects skin permeability barrier homeostasis Reviewed

M Denda, K Nakanishi, N Kumazawa

SKIN PHARMACOLOGY AND PHYSIOLOGY Vol. 18 ( 1 ) page： 36 - 41 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：KARGER

We previously demonstrated that the external electric potential affected skin barrier homeostasis. On the other hand, topical application of an ionic polymer formed a diffusion electric double layer on the surface of the skin. Thus, we evaluated effects of topical application of ionic polymers on the damaged skin barrier. Application of a nonionic polymer did not affect barrier recovery. Application of sodium salts of anionic polymers accelerated barrier recovery, while that of cationic polymers delayed it. Topical application of a sodium-exchange resin accelerated barrier recovery, but application of a calcium-exchange resin had no effect even when the resins had the same structure. Application of a chloride-exchange resin delayed barrier recovery. Topical application of ionic polymers influenced skin barrier homeostasis.

DOI： 10.1159/000081684

Fabrication of macroporous TiO2 monoliths for photonic applications Reviewed

J Konishi, K Fujita, K Nakanishi, K Hirao

Micromachining Technology for Micro-Optics and Nano-Optics III Vol. 5720 page： 233 - 240 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：SPIE-INT SOC OPTICAL ENGINEERING

Macroporous titania (TiO2) monoliths have been prepared by the sol-gel method including phase separation., and the light-scattering properties have been investigated by means of coherent backscattering. Macroporous TiO2 gels are obtained g a in the systems containing aqueous titania colloid and poly(ethylene oxide)(PEO). Three-dimensionally interconnected macroporous structure is formed when the transient structure of phase separation is fixed as the permanent morphology by the sol-gel transition. The domain size of macroporous TiO2 gels can be controlled reproducibly by adjusting the concentration of PEO. During the heat treatment above 1000 degrees C, the TiO2 skeleton is sintered into fully dense body and the crystalline structure is transformed from anatase to rutile, while maintaining macroporous morphology. We show that the rutile-type TiO2 -based macroporous monoliths are strongly scattering media for visible light.

DOI： 10.1117/12.591059

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Hierarchical macro-mesoporous silica monolith Reviewed

T Amatani, K Nakanishi, K Hirao, T Kodaira

Organic/Inorganic Hybrid Materials-2004 Vol. 847 page： 121 - 126 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：MATERIALS RESEARCH SOCIETY

Monolithic pure silica gels with hierarchical macro-mesoporous structure have been synthesized via spontaneous sol-gel process from silicon alkoxide using a structure-directing agent and a micelle-swelling agent. Monolithic body with well-defined co-continuous macropores is a result of concurrent phase separation and sol-gel transition induced by the polymerization reaction, whereas the mesopores are templated by the cooperative self-assembly of inorganic species, a structure-directing agent and a micelle-swelling agent. The following removal of surfactants by heat-treatment gives silica gels with hierarchical and fully accessible pores in discrete size ranges of micrometers and nanometers. The highly ordered 2D-hexagonal arrays of mesopores have been confirmed by X-ray diffraction measurements and FE-SEM observations. Furthermore, by further additions of the micelle-swelling agent, the mesostructural transition from well-ordered 2D-hexagonal arrays to mesostructured cellular foams (MCF) have been induced accompanied by minor modifications of the micrometer-range structure.

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Monolithic O/I-hybrids with hierarchically ordered meso- and macropores Reviewed

K Nakanishi, Y Kobayashi, T Amatani, K Hirao, T Kodaira

ORGANIC/INORGANIC HYBRID MATERIALS-2004 Vol. 847 page： 147 - 157 2005

Language：English Publishing type：Research paper (international conference proceedings) Publisher：MATERIALS RESEARCH SOCIETY

Organic-Inorganic hybrid gels with hierarchical well-defined macropores and supramolecularly templated mesopores with long-range orders have been synthesized in the systems of bridged poly(silsesquioxane) systems. Nonionic surfactants such as poly(ethyleneglycol)-poly(propyleneglycol)-poly(ethyleneglycol) triblock copolymers, EOPOEOs, were found to be effective both in inducing the phase separation to give macroporous morphology and in templating the mesopores with narrow size distribution. The number of methylene units in the bridge, changed from I to 6 in the present experiments, affected both the phase separation tendency and template strength. In the system containing 1,2-bis(trimethoxysilyl)ethane, 2D-hexagonal arrangement of mesopores have been prepared in the gel skeleton comprising the well-defined continuous macroporous network with an aid of micelle-stabilizing agent.

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Organic-inorganic hybrid poly(silsesquioxane) monoliths with controlled macro- and mesopores Reviewed

K Nakanishi, K Kanamori

JOURNAL OF MATERIALS CHEMISTRY Vol. 15 ( 35-36 ) page： 3776 - 3786 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Siloxane-based organic-inorganic hybrid monoliths with well-defined macropores and/or mesopores have been synthesized by a sol-gel process, accompanied by polymerization-induced phase separation. Using aklyltrialkoxysilanes and alkylene-bridged alkoxysilanes, two different categories of organosiloxane networks have been characterized in view of macroporosity (based on phase separation) and mesoporosity (supramolecularly templated by surfactants). While the alkyl-terminated poly(siloxane) networks exhibit substantial surface hydrophobicity accompanied by mechanical flexibility, the alkylene-bridged networks behave much more similarly to those prepared from tetraalkoxysilanes with regard to surface hydrophilicity, mechanical rigidness and mesopore-forming ability. The supramolecular templating of mesopores embedded in the gel skeletons (which comprise well-defined macroporous networks) has proven to give a wide variety of hierarchically-designed macro-mesoporous hybrid materials.

DOI： 10.1039/b508415f

Living radical polymerization in ruthenium-bearing size-exclusion silica gel column reactors Reviewed

M. Katsube, T. Ando, M. Ouchi, M. Sawamoto, K. Nakanishi, N. Ishizuka

Polymer Preprints, Japan Vol. 54 ( 2 ) page： 2491- 2005

Real space observation of phase separating structure in a sol-gel system Reviewed

H. Saito, K. Kanamori, K. Nakanishi, K. Hirao, Y. Nishikawa, H. Jinnai

Polymer Preprints, Japan Vol. 54 ( 1 ) page： 705- 2005

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<NAKANISHI Kazuki>

Papers - NAKANISHI Kazuki