最終更新日2017年02月01日

氏名

シモジマ アツシ

下嶋 敦

職名

教授

所属理工学術院

(先進理工学部)

連絡先

メールアドレス

メールアドレス
shimojima@waseda.jp

URL等

研究者番号
90424803

本属以外の学内所属

兼担

理工学術院(大学院先進理工学研究科)

学内研究所等

メソスケール材料研究所

研究所員 2014年-2014年

メソスケール材料研究所

研究所員 2015年-

所属学協会

日本MRS

日本ゾルゲル学会

化学工学会

アメリカ化学会

高分子学会

ゼオライト学会

日本セラミックス協会

日本化学会

受賞

第61回)日本セラミックス協会 進歩賞

2007年01月

研究分野

科研費分類

工学 / 材料工学 / 無機材料・物性

化学 / 材料化学 / 無機工業材料

論文

Diol-linked Microporous Networks of Cubic Siloxane Cages

Y. Wada, K. Iyoki, A. Sugawara-Narutaki, T. Okubo, and A. Shimojima

Chem. Eur. J.19p.1700 - 17052013年-

DOI

Facile Synthesis of Well-dispersed Hollow Mesoporous Silica Nanoparticles Using Iron Oxide Nanoparticles as Template

T. Ikuno, A. Nomura, K. Iyoki, T. Okubo, and A. Shimojima

Chem. Lett.42(3)p.316 - 3172013年-

Formation of Hierarchically Organized Zeolites by Sequential Intergrowth

W. Chaikittisilp, Y. Suzuki, R. R. Mukti, T. Suzuki, K. Sugita, K. Itabashi, A. Shimojima, and T. Okubo

Angew. Chem. Int. Ed.52(12)p.3355 - 33592013年-

DOI

Synthesis of Monodisperse Organosilica Nanoparticles with Hollow Interiors and Porous Shells Using Silica Nanosphres as Templates

Koike, Natsume; Ikuno, Takaaki; Okubo, Tatsuya; Shimojima, Atsushi

Chem. Commun.49p.4998 - 50002013年-

DOI

Porous Siloxane-Organic Hybrid with Ultrahigh Surface Area through Simultaneous Polymerization-Destruction of Functionalized Cubic Siloxane Cages

W. Chaikittisilp, M. Kubo, T. Moteki, A. Sugawara-Narutaki, A. Shimojima, and T. Okubo

J. Am. Chem. Soc.133(35)p.13832 - 138352011年-

Synthesis of Silicalite-1 using a Disiloxane-based Structure-directing Agent

H. Ishii, K. Itabashi, T. Okubo, and A. Shimojima

Microporous Mesoporous Mater.139(1-3)p.158 - 1632011年-

Formation of Reactive Microporous Networks from Alkoxyvinylsilylated Siloxane Cages

Hagiwara, Yoshiaki;Shimojima, Atsushi;Kuroda, Kazuyuki

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN83(4)p.424 - 4302010年-2010年

DOIWoS

詳細

ISSN:0009-2673

Effect of organic additives on the formation of alkylsiloxane mesophases

Shimojima, Atsushi;Sakurai, Mikako;Kuroda, Kazuyuki;Okubo, Tatsuya

JOURNAL OF COLLOID AND INTERFACE SCIENCE350(1)p.155 - 1602010年-2010年

DOIWoS

詳細

ISSN:0021-9797

Synthesis of mesostructured silica from monoalkyl-substituted double five-ring units

Shimojima, Atsushi;Kuge, Hideki;Kuroda, Kazuyuki

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY57(3)p.263 - 2682011年-2011年

DOIWoS

詳細

ISSN:0928-0707

Utilization of Alkoxysilyl Groups for the Creation of Structurally Controlled Siloxane-Based Nanomaterials

Kuroda, Kazuyuki;Shimojima, Atsushi;Kawahara, Kazufumi;Wakabayashi, Ryutaro;Tamura, Yasuhiro;Asakura, Yusuke;Kitahara, Masaki

CHEMISTRY OF MATERIALS26(1)p.211 - 2202014年-2014年

DOIWoS

詳細

ISSN:0897-4756

Azobenzene-siloxane hybrids with lamellar structures from bridge-type alkoxysilyl precursors

Guo, Sufang;Chaikittisilp, Watcharop;Okubo, Tatsuya;Shimojima, Atsushi

RSC ADVANCES4(48)p.25319 - 253252014年-2014年

DOIWoS

詳細

ISSN:2046-2069

Molecularly Designed Nanoparticles by Dispersion of Self-Assembled Organosiloxane-Based Mesophases

Sakamoto, Shigeru;Tamura, Yasuhiro;Hata, Hideo;Sakamoto, Yasuhiro;Shimojima, Atsushi;Kuroda, Kazuyuki

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION53(35)p.9173 - 91772014年-2014年

DOIWoS

詳細

ISSN:1433-7851

Precision synthesis of polymers tailored towards directed formation and arrangement of silica nanomaterials

Landenberger, Kira B.;Shinke, Yu;Oda, Yukari;Kanazawa, Arihiro;Kanaoka, Shokyoku;Aoshima, Sadahito;Tsuboike, Sachio;Zhou, Shujun;Sugawara-Narutaki, Ayae;Okubo, Tatsuya;Shimojima, Atsushi

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY2482014年-2014年

WoS

詳細

ISSN:0065-7727

Synthesis of colloidal Janus nanoparticles by asymmetric capping of mesoporous silica with phenylsilsesquioxane

Ujiie, Hiroto;Shimojima, Atsushi;Kuroda, Kazuyuki

CHEMICAL COMMUNICATIONS51(15)p.3211 - 32142015年-2015年

PubMedDOIWoS

詳細

ISSN:1359-7345

概要::Colloidal mesoporous silica nanoparticles asymmetrically capped with non-porous phenylsilsesquioxane have been prepared by adding phenyltriethoxysilane to an aqueous dispersion of mesostructured silica-surfactant composite nanoparticles. The integration of colloidal stability, mesoporosity and the Janus structure is quite promising for materials design applicable in various fields, including catalysis, biomedicine and coatings.

Si Substrate as a SiO2 Source for the Preparation of Mesoporous SiO2-TiO2 Thin Films

Hara, Shintaro;Miyata, Hirokatsu;Takahashi, Masahiko;Shimojima, Atsushi;Kuroda, Kazuyuki

CHEMISTRY LETTERS44(3)p.372 - 3742015年-2015年

DOICiNiiWoS

詳細

ISSN:0366-7022

概要:A Si substrate has been proved to be used as a SiO2 source for the preparation of mesoporous silica–titania thin films with cylindrical mesochannels. Exposing mesostructured titania–surfactant thin films to aqueous NH3 vapor reinforces the pore walls with uniformly distributed silicate species, which retain the mesostructure after calcination.

Regular assembly of cage siloxanes by hydrogen bonding of dimethylsilanol groups

Sato, Naoto; Kuroda, Yoshiyuki; Abe, Takuya; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemical Communications51(55)p.11034 - 110372015年07月-2015年07月 

DOIScopusWoS

詳細

ISSN:13597345

概要:© The Royal Society of Chemistry. A new class of ordered silica-based materials has been prepared by hydrogen bond-directed assembly of cage siloxanes modified with dimethylsilanol groups, providing a soft-chemical approach to crystalline silica materials with molecularly designed architectures.

Factors Governing the Formation of Hierarchically and Sequentially Intergrown MFI Zeolites by Using Simple Diquaternary Ammonium Structure-Directing Agents

Keoh, Sye Hoe; Chaikittisilp, Watcharop; Muraoka, Koki; Mukti, Rino R.; Shimojima, Atsushi; Kumar, Prashant; Tsapatsis, Michael; Okubo, Tatsuya

Chemistry of Materials28(24)p.8997 - 90072016年12月-2016年12月 

DOIScopusWoS

詳細

ISSN:08974756

概要:© 2016 American Chemical Society.Zeolites with hierarchical structures are of particular interest because such structures can improve molecular diffusion, particularly that of bulky molecules. N,N,N,N′,N′,N′-Hexapropylpentanediammonium cations (Pr6-diquat-5), a simple diquaternary ammonium organic structure-directing agent (OSDA), can direct the formation of hierarchically and sequentially intergrown MFI zeolites without employing any mesoporogens. In this paper, the effects of OSDAs having structures similar to Pr6-diquat-5 but different lengths of alkyl spacers and/or different substituting groups on the phase selectivity and morphology of the resulting zeolites are presented. It was revealed that the number of carbon atoms between two charged nitrogens in the OSDAs significantly affected the intergrowth and morphology of the crystals formed. In addition, the propyl-substituted OSDAs were found to be very selective to the formation of MFI zeolite, whereas the butyl-substituted OSDAs were not. For Pr6-diquat-5, the condition for the formation of hierarchically and sequentially intergrown MFI zeolites was somewhat narrow with the optimized molar composition of 1 SiO2:0.2 Pr6-diquat-5:0.375-0.500 KOH:200 H2O:4 EtOH. Defect lines observed on the obtained zeolite crystals by a transmission electron microscope were considered to be connectors for such intergrowths. The unique intergrowth formed by Pr6-diquat-5 was surmised to be due to the unusual fitting of Pr6-diquat-5 inside the channels of MFI zeolite, which was explained by comparing molecular dimensions and stabilization energies of each OSDA.

Si Substrate as a SiO2 Source for the Preparation of Mesoporous SiO2–TiO2 Thin Films

Hara Shintaro;Miyata Hirokatsu;Takahashi Masahiko;Shimojima Atsushi;Kuroda Kazuyuki

Chemistry Letters0(0)2015年-2015年

CiNii

詳細

ISSN:0366-7022

概要:Si substrate has been proved to be used as a SiO2 source for the preparation of mesoporous silica–titania thin films with cylindrical mesochannels. By the exposure of mesostructured titania–surfactant thin films to aqueous NH3 vapor, the pore walls are reinforced with uniformly distributed silicate species, which retains the mesostructure after calcination.

Interlayer Condensation of Protonated Layered Silicate Magadiite through Refluxing in N-Methylformamide

Asakura Yusuke;Hosaka Nami;Osada Shimon;Terasawa Taichi;Shimojima Atsushi;Kuroda Kazuyuki

Bulletin of the Chemical Society of Japan88(9)p.1241 - 12492015年-2015年

CiNii

詳細

ISSN:0009-2673

概要:Interlayer-condensed materials of protonated layered silicate (magadiite) are synthesized by refluxing in N-methylformamide (NMF) and the subsequent calcination. The obtained materials possess 2–3 times higher surface areas than calcined protonated magadiite, depending on the time of refluxing. NMF molecules in the interlayer spaces are converted to organic substances with higher thermal stability during the refluxing, which is useful for the control of the stacking sequence of silicate layers and for the following interlayer condensation to increase the microporosity. The microporosity of the material obtained by the treatment of protonated magadiite with NMF at r.t. and the subsequent calcination is similar to that of simply calcined protonated magadiite, indicating that the retention of thermally stable substances in the interlayer is critical for the increase in the pore volume and surface area of the derivative from magadiite. The method reported here will stimulate re-estimation of a large number of known layered silicate–organic intercalation compounds as possible candidates for the preparation of porous silica by interlayer condensation.

Selected Paper : Use of Mesoporous Silica Modified with Titanium Oxide as a Template for Preparation of Mesoporous Carbon Incorporating TiO₂ Nanocrystals

Kitahara Masaki;Suzuki Kohei;Kubara Saori;Shimasaki Yuta;Shimojima Atsushi;Wada Hiroaki;Kuroda Kazuyuki

Bulletin of the Chemical Society of Japan89(10)p.1207 - 12112016年-2016年

CiNii

詳細

ISSN:0009-2673

概要:

Mesoporous silica modified with titanium oxide is shown to be useful as a template for the preparation of mesoporous carbon incorporating TiO2 nanocrystals. The nanocomposite was prepared by deposition of carbon within the mesoporous silica template modified with titanium oxide, and subsequent template removal with NaOH (aq). The high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image of the prepared nanocomposite clearly showed that small TiO2 nanocrystals embedded on mesoporous carbon were formed. The Si–O–Ti bonds between mesoporous silica and titanium oxide layers are effective to suppress the migration of the Ti species, resulting in the formation of the TiO2 nanocrystals.

かご状元素ブロックを用いたシロキサン系多孔体の構築

佐藤 尚人;和田 宏明;下嶋 敦;黒田 一幸

粉体および粉末冶金64(3)p.126 - 1292017年-2017年

CiNii

詳細

概要:

Construction of nanoarchitectures using cage siloxane oligomers as element blocks is of much interest because of its excellent potential for creating novel porous materials. In this review, our recent work on the fabrication of siloxane-based nanostructures from cage siloxanes is presented. The arrangement of cage siloxanes units is controlled by various methods, including amphiphilic self-assembly and hydrogen bonding of silanol groups, toward the preparation of well-defined porous siloxane-based materials.

Cubic Siloxanes with Both Si−H and Si−OtBu Groups for Site-Selective Siloxane Bond Formation

Saito, Shohei; Yamasue, Nao; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemistry - A European Journal22(39)p.13857 - 138642016年09月-2016年09月 

DOIScopusWoS

詳細

ISSN:09476539

概要:© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCage-type siloxanes have attracted increasing attention as building blocks for silica-based nanomaterials as their corners can be modified with various functional groups. Cubic octasiloxanes incorporating both Si−H and Si−OtBu groups [(tBuO)nH8−nSi8O12; n=1, 2 or 7] have been synthesized by the reaction of octa(hydridosilsesquioxane) (H8Si8O12) and tert-butyl alcohol in the presence of a Et2NOH catalyst. The Si−H and Si−OtBu groups are useful for site-selective formation of Si−O−Si linkages without cage structure deterioration. The Si−H group can be selectively hydrolyzed to form a Si−OH group in the presence of Et2NOH, enabling the formation of the monosilanol compound (tBuO)7(HO)Si8O12. The Si−OH group can be used for either intermolecular condensation to form a dimeric cage compound or silylation to introduce new reaction sites. Additionally, the alkoxy groups of (tBuO)7HSi8O12 can be treated with organochlorosilanes in the presence of a BiCl3 catalyst to form Si−O−Si linkages, while the Si−H group remains intact. These results indicate that such bifunctional cage siloxanes allow for stepwise Si−O−Si bond formation to design new siloxane-based nanomaterials.

Selective Formation of Alkoxychlorosilanes and Organotrialkoxysilane with Four Different Substituents by Intermolecular Exchange Reaction

Komata, Yuma;Yoshikawa, Masashi;Tamura, Yasuhiro;Wada, Hiroaki;Shimojima, Atsushi;Kuroda, Kazuyuki

Chemistry-An Asian Journal11(22)p.3225 - 32332016年-2016年

DOIWoS

詳細

ISSN:1861-4728

Regular assembly of cage siloxanes by hydrogen bonding of dimethylsilanol groups.

Sato Naoto;Kuroda Yoshiyuki;Abe Takuya;Wada Hiroaki;Shimojima Atsushi;Kuroda Kazuyuki

Chemical communications (Cambridge, England)51(55)2015年-2015年

PubMedDOI

詳細

ISSN:1364-548X

概要::A new class of ordered silica-based materials has been prepared by hydrogen bond-directed assembly of cage siloxanes modified with dimethylsilanol groups, providing a soft-chemical approach to crystalline silica materials with molecularly designed architectures.

Preparation of core-shell mesoporous silica nanoparticles with bimodal pore structures by regrowth method

Ishii, Hirotaka; Ikuno, Takaaki; Shimojima, Atsushi; Shimojima, Atsushi; Okubo, Tatsuya

Journal of Colloid and Interface Science448p.57 - 642015年06月-2015年06月 

DOIScopus

詳細

ISSN:00219797

概要:© 2015 Elsevier Inc. Core-shell structured mesoporous silica nanoparticles (MSNs) with different pore characteristics in the cores and shells have been prepared by the regrowth method. Adding a silica source to a dispersion of presynthesized silica-surfactant composite nanoparticles with two-dimensional hexagonal mesostructures results in regrowth in preference to generation of new particles. Core-shell MSNs with bimodal porosities are easily obtained by adding a pore-expanding agent, 1,3,5-trimethylbenzene, in either the core or shell formation step. Detailed characterization of the core-shell MSNs reveals that the shells consist of disordered arrangements of relatively large or small pores and that the pore sizes in the cores change when the shells formed. Core-shell MSNs will be useful for controlling the release rates of the encapsulated guest molecules and for protecting internal pores from being plugged by other species.

Photoinduced Bending of Self-Assembled Azobenzene-Siloxane Hybrid

Guo, Sufang; Matsukawa, Kimihiro; Miyata, Takashi; Okubo, Tatsuya; Kuroda, Kazuyuki; Kuroda, Kazuyuki; Shimojima, Atsushi

Journal of the American Chemical Society137(49)p.15434 - 154402015年12月-2015年12月 

DOIScopus

詳細

ISSN:00027863

概要:© 2015 American Chemical Society.A novel azobenzene-siloxane hybrid material displaying photoinduced macroscopic motions has been prepared by one-step organosilane self-assembly. Two types of alkoxysilane precursors with either pendant or bridging azobenzene groups were synthesized via thiol-ene click reactions. Hybrid films with well-ordered lamellar structures were obtained by hydrolysis and polycondensation of these precursors. The film with solely pendant azobenzene groups showed reversible and rapid d-spacing variation upon UV-vis irradiation, which was induced by the trans-cis isomerization of azobenzene moieties. The flexible, free-standing film obtained by co-condensation of two types of precursors showed reversible bending-unbending motions upon UV-vis irradiation. The partial cross-linking between the siloxane layers by bridging azobenzene groups was crucial for photoinduced distortion of the film. This film possesses high elastic modulus, good thermal stability, and shows large amplitude of photoinduced bending-unbending over a wide temperature range. This is the first report on photoinduced macroscopic motions of azobenzene-containing siloxane-based materials. These materials possess great potential for applications in smart devices and energy conversion systems.

The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single-Crystalline Ordered Mesoporous Nb-TiO2 and Plate-like Nb-TiO2 with Ordered Mesoscale Dimples

Kitahara, Masaki; Shimasaki, Yuta; Matsuno, Takamichi; Kuroda, Yoshiyuki; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemistry - A European Journal21(37)p.13073 - 130792015年09月-2015年09月 

PubMedDOIScopus

詳細

ISSN:09476539

概要:© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Highly ordered mesoporous niobium-doped TiO2 with a single-crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb-doped TiO2. The XPS measurements of Nb-doped TiO2 showed the presence of Nb5+ and correspondingly Ti3+. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate-like TiO2 with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals.

Nanoparticle Vesicles with Controllable Surface Topographies through Block Copolymer-Mediated Self-Assembly of Silica Nanospheres

Zhou, Shujun; Sugawara-Narutaki, Ayae; Sugawara-Narutaki, Ayae; Tsuboike, Sachio; Wang, Junzheng; Shimojima, Atsushi; Shimojima, Atsushi; Okubo, Tatsuya

Langmuir31(48)p.13214 - 132202015年11月-2015年11月 

PubMedDOIScopus

詳細

ISSN:07437463

概要:© 2015 American Chemical Society.Silica nanoparticle vesicles (NPVs) with encapsulating capability and surface permeability are highly attractive in nanocatalysis, biosensing, and drug delivery systems. Herein, we report the facile fabrication of silica NPVs composed of a monolayer of silica nanospheres (SNSs, ca. 15 nm in diameter) through the block copolymer-mediated self-assembly of SNSs. The silica NPVs gain different surface topographies, such as raspberry- and brain coral-like topographies, under controlled heat treatment conditions. The vesicular assembly of SNSs is successful with a series of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) block copolymers, and the size of NPVs can be tuned by changing their molecular weight. The polymer is easily extracted from the NPVs with their colloidal dispersibility and structural integrity intact. The polymer-free silica NPVs further serve as a reaction vessel and host for functional materials such as tin oxide nanoparticles.

Usefulness of Mesoporous Silica as a Template for the Preparation of Bundles of Bi Nanowires with Precisely Controlled Diameter below 10 nm

Kitahara, Masaki; Kamila, Hasbuna; Shimojima, Atsushi; Wada, Hiroaki; Mori, Takao; Terasaki, Ichiro; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemistry - An Asian Journal11(6)p.900 - 9052016年03月-2016年03月 

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ISSN:18614728

概要:© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. The reduction of the diameter of Bi nanowires below 10 nm has been an important target because of the theoretical prediction with regard to significant enhancement in thermoelectric performance by size reduction. In this study, we have demonstrated the usefulness of mesoporous silica with tunable pore size as a template for the preparation of thin Bi nanowires with diameters below 10 nm. Bi was deposited within the templates through a liquid phase deposition using hexane and 1,1,3,3-tetramethyldisiloxane as a solvent and reducing agent, respectively. Bundles of thin Bi nanowires with non-crystalline frameworks were successfully obtained after the template removal. The diameter was precisely controlled between about 6 nm and 9 nm. The judicious choices of mesoporous silica and deposition conditions are critical for the successful preparation. The reliable formation of such thin Bi nanowires reported here opens up exciting new possibilities.

Hollow Inorganic Spheres

Shimojima, Atsushi

The Sol-Gel Handbook1-3p.345 - 3722015年09月-2015年09月 

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概要:© 2015 Wiley-VCH Verlag GmbH & Co. KGaA. This chapter focuses on the hollow oxide nanoparticles prepared by liquid-phase deposition methods. This chapter reviewed recent advances in the preparation of hollow oxide nanoparticles by liquid-phase deposition methods. Among hollow inorganic particles, silica-based particles are the most extensively studied because of their ease of synthesis, structural and compositional diversities, and wide range of applications such as in coatings catalysis, adsorption, and drug delivery system (DDS). Hollow silica particles can be synthesized by either templating or template-free methods. Hollow particles with various compositions, controlled shell structures, and controlled shapes and sizes have successfully been obtained by employing either template or template-free method, and many interesting properties arising from their unique structural features have been reported. Large-scale and low-cost production by environment-friendly processes promises practical applications in many fields.

A Single-Crystalline Mesoporous Quartz Superlattice

Matsuno, Takamichi; Kuroda, Yoshiyuki; Kitahara, Masaki; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Angewandte Chemie - International Edition55(20)p.6008 - 60122016年05月-2016年05月 

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詳細

ISSN:14337851

概要:© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. There has been significant interest in the crystallization of nanostructured silica into α-quartz because of its physicochemical properties. We demonstrate a single-crystalline mesoporous quartz superlattice, a silica polymorph with unprecedentedly ordered hierarchical structures on both the several tens of nanometers scale and the atomic one. The mesoporous quartz superlattice consists of periodically arranged α-quartz nanospheres whose crystalline axes are mostly oriented in an assembly. The superlattice is prepared by thermal crystallization of amorphous silica nanospheres constituting a colloidal crystal. We found that the deposition of a strong flux of Li+ only on the surface of silica nanospheres is effective for crystallization. Order a double: A single-crystalline mesoporous quartz superlattice with periodic order on both the several tens of nanometer scale and the atomic scale is prepared by crystallization of amorphous silica nanospheres which constitute a colloidal crystal. The periodic arrangement of silica nanospheres is retained even though Li+ ions are used as a strong flux.

A photoresponsive azobenzene-bridged cubic silsesquioxane network

Guo, Sufang; Guo, Sufang; Okubo, Tatsuya; Kuroda, Kazuyuki; Kuroda, Kazuyuki; Shimojima, Atsushi

Journal of Sol-Gel Science and Technology79(2)p.262 - 2692016年08月-2016年08月 

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ISSN:09280707

概要:© 2016, Springer Science+Business Media New York.Abstract: An azobenzene (AZO)-bridged cubic silsesquioxane network exhibiting reversible photoisomerization behavior in nonpolar solvents has been prepared via hydrosilylation reaction between 4,4′-diallyloxy-azobenzene and octahydridosilsesquioxane (H8Si8O12; H-POSS). Approximately 70 % of the corner Si–H groups of H-POSS are reacted to form a three-dimensional gel network while maintaining the cubic siloxane structure. The dried gel has a high thermal stability, which is attributed to the highly cross-linked cubic silsesquioxane network where AZOs are covalently incorporated in the main chain. The gel exhibits reversible swelling behavior in nonpolar solvents during wetting–drying cycles. In toluene, a large extent of reversible trans–cis isomerization of the AZO moiety is observed. These results are promising for the design of a new class of photoresponsive materials applicable in host–guest chemistry. Graphical Abstract: [Figure not available: see fulltext.]

Fabrication of colloidal crystals composed of pore-expanded mesoporous silica nanoparticles prepared by a controlled growth method

Yamamoto, Eisuke; Mori, Seiya; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Nanoscale9(7)p.2464 - 24702017年02月-2017年02月 

DOIScopus

詳細

ISSN:20403364

概要:© The Royal Society of Chemistry.Colloidal crystals composed of mesoporous silica nanoparticles (MSNs) are expected to have various applications because of their unique hierarchical structures and tunable functions. The expansion of the mesopore size is important for introducing guest species which cannot be accommodated by using conventional colloidal crystals of MSNs; however, the preparation of MSNs with a controllable pore size, suitable for the fabrication of colloidal crystals, still remains a challenge. In this study, we fabricated colloidal crystals composed of pore-expanded MSNs using a sophisticated particle growth method to control the pore size of colloidal MSNs while retaining their monodispersity high enough to form colloidal crystals. By adding triisopropylbenzene (TIPB) only during the growth process with the stepwise addition of tetrapropoxysilane (TPOS), the particle size can be tuned from 60 nm to 100 nm, while the pore size can be tuned from 3 nm to ten plus several nm which is the largest size among the previous MSNs capable of forming colloidal crystals. These novel colloidal crystals should contribute to the expansion of nanomaterials science.

Direct Synthesis of Highly Designable Hybrid Metal Hydroxide Nanosheets by Using Tripodal Ligands as One-Size-Fits-All Modifiers

Kuroda, Yoshiyuki; Koichi, Tatsuyuki; Muramatsu, Keisuke; Yamaguchi, Kazuya; Mizuno, Noritaka; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemistry - A European Journal23(21)p.5023 - 50322017年04月-2017年04月 

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ISSN:09476539

概要:© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimBrucite-type layered metal hydroxides are prepared from diverse metallic elements and have outstanding functions; however, their poor intercalation ability significantly limits their chemical designability and the use of their potentially ultrahigh surface areas and unique properties as two-dimensional nanosheets. Here, we demonstrate that tripodal ligands (RC(CH2OH)3, R=NH2, CH2OH, or NHC2H4SO3H) are useful as “one-size-fits-all” modifiers for the direct synthesis of hybrid metal hydroxide nanosheets with various constituent metallic elements (M=Mg, Mn, Fe, Co, Ni, or Cu) and surface functional groups. The hybrid nanosheets are formed directly from solution phases, and they are stacked into a turbostratic layered structure. The ligands form tridentate Mg-O-C bonds with brucite layers. The hybrid brucite intercalates various molecules and is exfoliated into nanosheets at room temperature, although the non-modified material does not intercalate any molecules. Consequently, both the constituent metallic elements and surface functional groups are freely designed by the direct synthesis.

Direct Observation of the Outermost Surfaces of Mesoporous Silica Thin Films by High Resolution Ultralow Voltage Scanning Electron Microscopy

Kobayashi, Maho; Susuki, Kyoka; Otsuji, Haruo; Sakuda, Yusuke; Asahina, Shunsuke; Kikuchi, Naoki; Kanazawa, Toshiyuki; Kuroda, Yoshiyuki; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Langmuir33(9)p.2148 - 21562017年03月-2017年03月 

DOIScopus

詳細

ISSN:07437463

概要:© 2017 American Chemical Society.The properties of the outermost surfaces of mesoporous silica thin films are critical in determining their functions. Obtaining information on the presence or absence of silica layers on the film surfaces and on the degree of mesopore opening is essential for applications of surface mesopores. In this study, the outermost surfaces of mesoporous silica thin films with 3-dimensional orthorhombic and 2-dimensional hexagonal structures were observed using ultralow voltage high resolution scanning electron microscopy (HR-SEM) with decelerating optics. SEM images of the surfaces before and after etching with NH4F were taken at various landing voltages. Comparing the images taken under different conditions indicated that the outermost surfaces of the nonetched mesoporous silica thin films are coated with a thin layer of silica. The images taken at an ultralow landing voltage (i.e., 80 V) showed that the presence or absence of surface silica layers depends on whether the film was etched with an aqueous solution of NH4F. The mesostructures of both the etched and nonetched films were visible in images taken at a conventional landing voltage (2 kV); hence, the ultralow landing voltage was more suitable for analyzing the outermost surfaces. The SEM observations provided detailed information about the surfaces of mesoporous silica thin films, such as the degree of pore opening and their homogeneities. AFM images of nonetched 2-dimensional hexagonal mesoporous silica thin films show that the shape of the silica layer on the surface of the films reflects the curvature of the top surface of the cylindrical mesochannels. SEM images taken at various landing voltages are discussed, with respect to the electron penetration range at each voltage. This study increases our understanding of the surfaces of mesoporous silica thin films, which may lead to potential applications utilizing the periodically arranged mesopores on these surfaces.

Construction of siloxane-based porous materials by using cage-Type element blocks

Sato, Naoto; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy64(3)p.126 - 1292017年03月-2017年03月 

Scopus

詳細

ISSN:05328799

概要:Construction of nanoarchitectures using cage siloxane oligomers as element blocks is of much interest because of its excellent potential for creating novel porous materials. In this review, our recent work on the fabrication of siloxane-based nanostructures from cage siloxanes is presented. The arrangement of cage siloxanes units is controlled by various methods, including amphiphilic self-Assembly and hydrogen bonding of silanol groups, toward the preparation of well-defined porous siloxane-based materials.

Formation of Nanogrooves with Sub-5 nm Periodicity Using Local Silicification at the Interspace between a Si Substrate and Lyotropic Liquid Crystals

Hara, Shintaro; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

ACS Nano11(5)p.5160 - 51662017年05月-2017年05月 

DOIScopus

詳細

ISSN:19360851

概要:© 2017 American Chemical Society. Bottom-up fabrication of nanopatterns with single nanometer-scale periodicity is quite challenging. In this study, we have focused on the use of the outermost convex surfaces of lyotropic liquid crystals (LLCs) as a template. Periodically arrayed single nanometer-scale nanogrooves consisting of silica are successfully formed on a Si substrate covered with LLCs composed of cylindrical micelles of cetyltrimethylammonium chloride. Soluble silicate species are generated from the Si substrate by a treatment with an NH 3 -water vapor mixture, infilling the interspaces between the Si substrate and the LLCs. The cross section of the nanogrooves has a symmetrical sawtooth-like profile with a periodicity of 4.7 nm, and the depth of each nanogroove is around 2 nm. Uniaxial alignment of the nanogrooves can be achieved using micrometer-scale grooves fabricated by a focused ion beam technique. Although formed nanogrooves contain defects, such as bends and discontinuities, this successful concept provides a novel fabrication method of arrayed concave patterns with sub-5 nm periodicity on the surfaces of Si substrates.

Role of Cubic Siloxane Cages in Mesostructure Formation and Photoisomerization of Azobenzene–Siloxane Hybrid

Guo Sufang;Sasaki Jun;Tsujiuchi Shiho;Hara Shintaro;Wada Hiroaki;Kuroda Kazuyuki;Shimojima Atsushi

Chemistry Letters46(8)p.1237 - 12392017年-2017年

CiNii

詳細

概要:

A mesostructured siloxane-based hybrid film is formed by the self-assembly of cubic, double-four-ring (D4R) siloxanes mono-functionalized with azobenzene. The azobenzene groups in the film exhibit reversible and a high degree of transcis isomerization upon UV–vis irradiation. The bulky D4R cages play an important role in both the formation of cylindrical assemblies and the improvement of the photoisomerization behavior as compared with conventional azobenzene–siloxane hybrid materials.

Preparation of Mesoporous Basic Oxides through Assembly of Monodispersed Mg–Al Layered Double Hydroxide Nanoparticles

Oka, Yuya; Kuroda, Yoshiyuki; Kuroda, Yoshiyuki; Matsuno, Takamichi; Kamata, Keigo; Kamata, Keigo; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemistry - A European Journal23(39)p.9362 - 93682017年07月-2017年07月 

DOIScopus

詳細

ISSN:09476539

概要:© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Mesoporous basic Mg–Al mixed metal oxides (MMOs) with a high surface area and large pore size have been prepared through the assembly of monodispersed layered double hydroxide nanoparticles (LDHNPs) with block copolymer templates. The particle sizes of the LDHNPs were mainly controlled by varying the concentration of tris(hydroxymethyl)aminomethane (THAM), which was used as a surface stabilizing agent. LDHNPs and micelles of a block copolymer (Pluronic F127) were assembled to form a composite. The composites were calcined to transform them into mesoporous MMOs and to remove the templates. The Brunauer–Emmett–Teller surface areas, mesopore sizes, and pore volumes increased as a result of using the templates. Moreover, the pore sizes of the mesoporous MMOs could be controlled by using LDHNPs of different sizes. The mesoporous MMOs prepared from the LDHNPs showed much higher catalytic activity than a conventional MMO catalyst for the Knövenagel condensation of ethyl cyanoacetate with benzaldehyde. The mesoporous MMO catalyst prepared using the smallest LDHNPs, about 12 nm in size, showed the highest activity. Therefore, the use of monodispersed LDHNPs and templates is effective for preparing highly active mesoporous solid base catalysts.

Synthesis of a Single-Crystalline Macroporous Layered Silicate from a Macroporous UTL-Type Zeolite and Its Accelerated Intercalation

Asakura, Yusuke; Asakura, Yusuke; Kawaura, Naoki; Kuroda, Yoshiyuki; Kuroda, Yoshiyuki; Koike, Masakazu; Wada, Hiroaki; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Chemistry - A European Journal23(46)p.11022 - 110292017年08月-2017年08月 

DOIScopus

詳細

ISSN:09476539

概要:© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A single-crystalline macroporous layered silicate was obtained for the first time. Firstly, UTL-type zeolite with macropores was prepared hydrothermally under the presence of acetylene black as a macropore template and the subsequent calcination to remove the template. Double four-membered ring (d4r) units in the UTL framework were selectively dissolved to yield a layered silicate with macropores. Intercalation of tetrabutylammonium ions into the macroporous layered silicate is accelerated if compared with that into the same silicate without macropores, indicating the effectiveness of macropores due to easy diffusion. The layered silicate with macropores was converted into PCR-type zeolite with macropores, a hierarchically micro- and macroporous material, through interlayer condensation.

Thickness control of 3-dimensional mesoporous silica ultrathin films by wet-etching

Kobayashi, Maho; Susuki, Kyoka; Otani, Tomohiro; Enomoto, Shinpei; Otsuji, Haruo; Kuroda, Yoshiyuki; Wada, Hiroaki; Shimojima, Atsushi; Homma, Takayuki; Homma, Takayuki; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Nanoscale9(24)p.8321 - 83292017年06月-2017年06月 

DOIScopus

詳細

ISSN:20403364

概要:© 2017 The Royal Society of Chemistry. The thickness of 3-dimensional (3D) mesoporous silica ultrathin films was controlled at a single-nanometer scale by wet-etching. A drop casting method with an aqueous etchant of ammonium fluoride was effective in etching the surfaces of films in the direction perpendicular to their substrates. The decrease in the film thickness depends on the interface tension of etching solutions. The wettability of thin films also influences the etching. CoPt nanodots were electrodeposited within ultrathin silica films on Ru substrates to form CoPt nanodot patterns.

Organic-Free Synthesis of a Highly Siliceous Faujasite Zeolite with Spatially Biased Q4(nAl) Si Speciation

Oleksiak, Matthew D.; Muraoka, Koki; Hsieh, Ming Feng; Conato, Marlon T.; Conato, Marlon T.; Shimojima, Atsushi; Okubo, Tatsuya; Chaikittisilp, Watcharop; Rimer, Jeffrey D.

Angewandte Chemie - International Edition56(43)p.13366 - 133712017年10月-2017年10月 

DOIScopus

詳細

ISSN:14337851

概要:© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim We report the most siliceous FAU-type zeolite, HOU-3, prepared via a one-step organic-free synthesis route. Computational studies indicate that it is thermodynamically feasible to synthesize FAU with SAR=2–7, though kinetic factors seemingly impose a more restricted upper limit for HOU-3 (SAR≈3). Our findings suggest that a slow rate of crystallization and/or low concentration of Na + ions in HOU-3 growth mixtures facilitate Si incorporation into the framework. Interestingly, Q 4 (nAl) Si speciation measured by solid-state NMR can only be modeled with a few combinations of Al positioning at tetrahedral sites in the crystal unit cell, indicating the distribution of Si(-O-Si) 4−n (-O-Al) n species is spatially biased as opposed to being random. Achieving higher SAR is desirable for improved zeolite (hydro)thermal stability and enhanced catalytic performance, which we demonstrate in benchmark tests that show HOU-3 is superior to commercial zeolite Y.

Nanospace-Mediated Self-Organization of Nanoparticles in Flexible Porous Polymer Templates

Kuroda, Yoshiyuki; Kuroda, Yoshiyuki; Muto, Itaru; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Langmuir33(36)p.9137 - 91432017年09月-2017年09月 

DOIScopus

詳細

ISSN:07437463

概要:© 2017 American Chemical Society. Self-organization is a fundamental process for the construction of complex hierarchically ordered nanostructures, which are widespread in biological systems. However, precise control of size, shape, and surface properties is required for self-organization of nanoparticles. Here, we demonstrate a novel self-organization phenomenon mediated by flexible nanospaces in templates. Inorganic nanoparticles (e.g., silica, zirconia, and titania) are deposited in porous polymer thin films with randomly distributed pores on the surface, leaving a partially filled nanospace in each pore. Heating at temperatures beyond the glass transition temperature of the template leads to self-organization of the inorganic nanoparticles into one-dimensional chainlike networks. The self-organization is mediated by the deformation and fusion of the residual nanospaces, and it can be rationally controlled by sequential heat treatments. These results show that a nanospace, defined by the nonexistence of matter, interacts indirectly with matter and can be used as a component of self-organization systems.

Protecting and Leaving Functions of Trimethylsilyl Groups in Trimethylsilylated Silicates for the Synthesis of Alkoxysiloxane Oligomers

Yoshikawa, Masashi; Tamura, Yasuhiro; Wakabayashi, Ryutaro; Wakabayashi, Ryutaro; Tamai, Misa; Shimojima, Atsushi; Kuroda, Kazuyuki; Kuroda, Kazuyuki

Angewandte Chemie - International Edition56(45)p.13990 - 139942017年11月-2017年11月 

DOIScopus

詳細

ISSN:14337851

概要:© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The concept of protecting groups and leaving groups in organic synthesis was applied to the synthesis of siloxane-based molecules. Alkoxy-functionalized siloxane oligomers composed of SiO 4 , RSiO 3 , or R 2 SiO 2 units were chosen as targets (R: functional groups, such as Me and Ph). Herein we describe a novel synthesis of alkoxysiloxane oligomers based on the substitution reaction of trimethylsilyl (TMS) groups with alkoxysilyl groups. Oligosiloxanes possessing TMS groups were reacted with alkoxychlorosilane in the presence of BiCl 3 as a catalyst. TMS groups were substituted with alkoxysilyl groups, leading to the synthesis of alkoxysiloxane oligomers. Siloxane oligomers composed of RSiO 3 and R 2 SiO 2 units were synthesized more efficiently than those composed of SiO 4 units, suggesting that the steric hindrance around the TMS groups of the oligosiloxanes makes a difference in the degree of substitution. This reaction uses TMS groups as both protecting and leaving groups for SiOH/SiO − groups.

Spontaneous Crack Healing in Nanostructured Silica-Based Thin Films

Itoh, Shun; Kodama, Satoshi; Kobayashi, Maho; Hara, Shintaro; Wada, Hiroaki; Kuroda, Kazuyuki; Shimojima, Atsushi

ACS Nano査読有り11(10)p.10289 - 102942017年09月-2017年09月 

DOI

メソポーラスシリカナノ粒子の精密合成

山本 瑛祐;下嶋 敦;黒田 一幸

日本結晶成長学会誌44(2)p.82 - 872017年-2017年

CiNii

詳細

概要:

  Mesoporous silica nanoparticles have attracted great attention because of their potential applications as catalysts, drug/gene delivery carriers, and optical materials because of high surface area, large pore volume, transparency, biocompatibility, and high cell uptake efficiency. This review reports general preparation and applications of mesoporous silica nanoparticles, and our recent efforts on the preparation of well-dispersed mesoporous silica nanoparticles with precisely controlled particle size, pore size, functionality, and morphology.

外部研究資金

科学研究費採択状況

研究種別:新学術領域研究(研究領域提案型)

元素ブロックの配列制御に基づく光応答性有機シリカの創製

2015年-2016年

研究分野:元素ブロック高分子材料の創出

配分額:¥3120000

研究種別:基盤研究(B)

ナノポアを有するシロキサン系分子合成と機能開拓

2015年-2017年

研究分野:無機工業材料

配分額:¥8450000

研究種別:新学術領域研究(研究領域提案型)

元素ブロックの配列制御による光応答性有機シリカの創製

2013年-2014年

研究分野:元素ブロック高分子材料の創出

配分額:¥7020000

研究種別:新学術領域研究(研究領域提案型)

無機有機ハイブリッドクラスターの集積による多孔性融合マテリアルの創製

2013年-2014年

研究分野:融合マテリアル:分子制御による材料創成と機能開拓

配分額:¥5980000

研究種別:基盤研究(C)

シリカ系構造単位の設計による新規ナノ空間材料の創製

2012年-2014年

研究分野:無機工業材料

配分額:¥5460000

研究種別:基盤研究(B)

ナノビルディングユニットの精密合成とその自己集合による各種次元組織体の構築

2011年-2013年

研究分野:無機工業材料

配分額:¥20150000

研究種別:新学術領域研究(研究領域提案型)

有機シリカ系ハイブリッドクラスターの集積による多孔性ネットワークの構築

2011年-2012年

研究分野:融合マテリアル:分子制御による材料創成と機能開拓

配分額:¥5720000

研究種別:若手研究(B)

異方性構造ユニットからの結晶性シリカー有機ハイブリッド多孔体の創製

2010年-2011年

研究分野:無機工業材料

配分額:¥4030000

研究種別:基盤研究(B)

Step-by-Step合成法の開発による新規ゼオライトの創出と応用

2008年-2010年

研究分野:反応工学・プロセスシステム

配分額:¥18720000

研究種別:若手研究(B)

分子設計に基づく結晶性シリカメソ多孔体材料の創製

2007年-2008年

研究分野:無機工業材料

配分額:¥3670000

研究種別:基盤研究(B)

精密に設計された構造単位からの規則的シリカ系ナノ構造体の創製

2006年-2007年

研究分野:無機工業材料

配分額:¥15820000

学内研究制度

特定課題研究

自己組織化によるシリカ-ペプチドナノ組織体の創製

2013年度

研究成果概要:本研究課題では、生体分子であるアミノ酸やペプチドがSi-C結合を介してケイ素アルコキシドと連結した分子を設計し、その自己組織化・重合により新しいハイブリッド材料を創出することを目的としている。今回は、規則的な細孔を有するメソ多孔体...本研究課題では、生体分子であるアミノ酸やペプチドがSi-C結合を介してケイ素アルコキシドと連結した分子を設計し、その自己組織化・重合により新しいハイブリッド材料を創出することを目的としている。今回は、規則的な細孔を有するメソ多孔体をターゲットとした。シリカメソ多孔体を有機修飾することによって多様な機能を付与することができるが、特に、アミノ酸やペプチドによる細孔内修飾によって生体分子の吸着、キラル分離、酵素類似反応などへの応用が期待できる。本研究では、アミノ酸にトリアルコキシシリル(-Si(OR)3)基が連結された新規アルコキシシランを合成し、界面活性剤を鋳型として用いたアミノ酸修飾メソポーラスシリカの直接合成について検討した。各種アミノ酸(グリシン (Gly)、アラニン (Ala)、フェニルアラニン (Phe)など)のエチルエステルと3-イソシアネートプロピルトリエトキシシランとの反応により、尿素結合を介してトリエトキシシリル(TES)基が結合したTES-アミノ酸を合成した。TES-Glyについては、-COOH末端にもTES基を結合させた(TES-Gly-TES)。これらの分子をテトラエトキシシラン(Si(OEt)4)と様々なモル比(x : (1-x), x = 0-0.8)で混合し、カチオン性のアルキルトリメチルアンモニウムあるいは非イオン性界面活性剤の存在下、加水分解・縮重合させることによってメソ複合体を合成し、溶媒抽出によって界面活性剤の除去を行った。TES-アミノ酸はいずれも無色透明の油状物質であったが、TES-Gly-TESは結晶性の固体であった。各分子の1H,13C,29Si NMR測定により、アミノ酸部位とTES基、さらに尿素結合に帰属されるシグナルが観測された。TES-Gly, TES-Ala, TES-Pheの添加量をx = 0.2として得られたメソ構造体は、XRD、TEMにより2Dヘキサゴナル構造をもつことがわかった。窒素吸着測定の結果、x = 0の場合と比較して細孔径が減少したものの、メソ孔を有することが確認された。IRスペクトルからは、シロキサン骨格による吸収ピークのほかに、アミノ酸由来のピークが観測され、xの増加にともなってその強度が増加した。以上の結果から、細孔表面がアミノ酸で修飾されたメソポーラスシリカの合成が確認できた。一方、TES-Gly-TESを用いた場合も同様に多孔体が得られたが、この場合、アミノ酸部位はシリカ骨格内に組み込まれていると予想された。

生体に学ぶシリカ系自己修復材料の創製

2013年度

研究成果概要:自己修復材料は外部応力によって生じた損傷を自発的に修復する能力を有する材料であり、幅広い分野での応用が期待されている。生体系には様々な自己修復機能が存在するが、ある種の生体高分子は可逆的な水素結合を積極的に利用して高次構造の損傷を...自己修復材料は外部応力によって生じた損傷を自発的に修復する能力を有する材料であり、幅広い分野での応用が期待されている。生体系には様々な自己修復機能が存在するが、ある種の生体高分子は可逆的な水素結合を積極的に利用して高次構造の損傷を修復することが知られている。このような水素結合の可逆性を利用したポリマーの設計は最近非常に注目されており、熱可逆性高分子ゲルなどユニークな物性を持つ材料が報告されつつある。本研究では、従来の有機ポリマー系自己修復材料よりも高い安定性、優れた力学特性、そして高い修復能を有する新しい無機-有機ハイブリッド型の自己修復材料の設計を目的としている。低ガラス転移点、耐熱性、透明性、生体適合性などの特長を有する無機高分子であるポリジメチルシロキサン(PDMS)を用い、水素結合性有機基で修飾すると同時に、剛直な無機フィラーでありかつ架橋点としても働くケージ状シロキサンオリゴマーにグラフトすることによって、水素結合性の星形ポリマーの合成について検討した。ケージ状シロキサンオリゴマーは、テトラメチルアンモニウムイオン存在下でのケイ素アルコキシド(Si(OEt)4)の加水分解・重縮合反応によって得られるケイ酸8量体をジメチルクロロシランでシリル化した後、Si-H基をSi-Cl基に変換することで合成した。次に、環状トリシロキサンのアニオンリビング重合により分子量の制御されたPDMSを合成し、停止剤として上記のSi-Cl修飾型のシロキサンオリゴマーを添加することによって、シロキサンユニットあたり4~5本のPDMSがグラフトされたポリマーが形成されたことをNMR等で確認した。さらに、あらかじめPDMSの一部のメチル基をビニル基に置換し、それらを基点に水素結合性の有機基であるウレイドピリミジノンで修飾することによって、水素結合性ポリマーの合成に成功した。今後、ポリマーの構造と物性の相関について検討を行う予定である。

シロキサン系ビルディングブロックライブラリーの構築へ向けたシリル基置換反応の開拓

2015年度共同研究者:黒田一幸

研究成果概要:本研究ではアルコキシシロキサンオリゴマーの新規合成手法の開発を目的とし、トリメチルシリル(TMS)基とアルコキシシリル基の交換反応について検討した。塩化ビスマス触媒下、ヘキサメチルジシロキサン(HMDS)もしくはテトラキス(トリメ...本研究ではアルコキシシロキサンオリゴマーの新規合成手法の開発を目的とし、トリメチルシリル(TMS)基とアルコキシシリル基の交換反応について検討した。塩化ビスマス触媒下、ヘキサメチルジシロキサン(HMDS)もしくはテトラキス(トリメチルシロキシ)シラン(QM4)とクロロジメトキシメチルシランを反応させた。NMR分析により、HMDSの場合は、2個のTMS基がジメトキシメチルシリル基に置換された分子を、また、QM4の場合も 2, 3, 4個のTMS基が置換された分子の生成を確認した。以上より、TMS基を有するシロキサンオリゴマーからアルコキシシロキサンオリゴマーを得る新規ルートを開拓した。

有機構造規定剤の表面固定化に基づくセオライトのナノスケール形態制御

2015年度共同研究者:黒田一幸

研究成果概要:本研究では、ゼオライト結晶の配向、厚さ、サイズの制御を目指し、二つの四級アンモニウムイオンを有する有機構造規定剤(OSDA)を基板上に固定化する手法について検討した。新規OSDAとしてハロゲン化アルキル基を有する OSDAを合成し...本研究では、ゼオライト結晶の配向、厚さ、サイズの制御を目指し、二つの四級アンモニウムイオンを有する有機構造規定剤(OSDA)を基板上に固定化する手法について検討した。新規OSDAとしてハロゲン化アルキル基を有する OSDAを合成した後、架橋アミノ基を有する有機修飾アルコキシシランと反応させ、基板上に薄膜として塗布することで、OSDAの固定化に成功した。得られた薄膜は高い水熱安定性を有することから、ゼオライト形成の基板として有用であると考えられた。

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