Atsushi Shimojima

This paper reports on recent progress in the synthesis of nanostructured siloxane-organic hybrids based on the self-assembly of amphiphilic silicon-based precursors. A variety of ordered hybrid materials have been obtained by molecular design of the precursors. Alkoxysilanes and chlorosilanes with covalently attached hydrophobic organic tails are hydrolyzed to form amphiphilic molecules containing silanol groups, leading to the formation of layered (lamellar) structures. Transparent and oriented

Abstract Triethoxy(alkyl)silanes containing 12—18 carbon atoms in the alkyl groups were hydrolyzed and polycondensed to form ordered structured materials. The XRD pattern of each condensed product showed sharp diffraction peaks with higher orders. The basal spacings approximately corresponded to twice the extended molecular length of the alkyl groups, and increased linearly as a function of the alkyl chain length. The SEM images of the products exhibited a platy morphology, and the 29Si CP/MAS N

A novel self-assembly route to ordered silica-organic hybrids using well-defined siloxane oligomers with alkoxy functionality and covalently attached alkyl chains has been investigated. Various hybrid mesostructures were obtained by hydrolysis and polycondensation without the use of any structure-directing agents. The oligomers 1(Cn), having an alkylsilane core and three branched trimethoxysilyl groups, formed highly ordered lamellar phases when n = 14-18, while those with shorter alkyl chains f

Transparent thin films of layered inorganic−organic nanocomposites were prepared by the sol−gel reactions of alkyldimethylmethoxysilane, alkylmethyldimethoxysilane, and alkyltrimethoxysilane in the presence of tetramethoxysilane followed by spin-coating. The macroscopic homogeneity and the nanostructural ordering of the films were strongly affected by the degree of polycondensation in the precursor solutions. The formation of siloxane networks containing organosiloxane units was confirmed by 29S

Interlayer modification of a layered polysilicate kanemite was performed by silylation with mono-, di-, and trichloro(alkyl)silanes. The introduction of silyl groups into the interlayer region was confirmed by XRD, IR, 13C NMR, and 29Si NMR. The layered structures of the silylated products were confirmed by swelling behavior upon adsorption of n-alkyl alcohols. The amounts of attached alkylsilyl groups varied with the number of functional groups as well as the alkyl chain length in the silylatin

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSynthesis of Oriented Inorganic−Organic Nanocomposite Films from Alkyltrialkoxysilane−Tetraalkoxysilane MixturesAtsushi Shimojima, Yoshiyuki Sugahara, and Kazuyuki KurodaView Author Information Department of Applied Chemistry,Waseda University Ohkubo-3, Shinjuku-ku, Tokyo 169-8555, Japan Kagami Memorial Laboratory for Materials Science and Technology, Waseda University Nishiwaseda-2, Shinjuku-ku, Tokyo 169-0051, Japan Cite this: J. Am. Chem. Soc.

Siloxane-organic hybrids with well-ordered mesostructures were synthesized through the self-assembly of novel amphiphilic molecules that consist of cubic siloxane heads and hydrophobic alkyl tails. The monoalkyl precursors functionalized with ethoxy groups (C(n)H(2n+1)Si(8)O(12)(OEt)(7), 1 Cn, n=16, 18, and 20) were hydrolyzed under acidic conditions with the retention of the siloxane cages, leading to the formation of two-dimensional hexagonal phases by evaporation-induced self-assembly process

Multilayered inorganic−organic hybrids were prepared by cohydrolysis and polycondensation of alkyltriethoxysilanes (CnTES, n = 8−18) and tetraethoxysilane (TEOS). Thin films were deposited from homogeneous solutions containing the oligomeric species by dip-coating. Self-assembly of co-condensed oligomers into lamellar structures depended essentially on the alkyl chain length of CnTES and the temperature of the solutions. By controlling the solution temperature during the dip-coating process, tra

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.

Novel tert-alkoxysilanetriols (ROSi(OH)(3), R=adamantyl and 3-ethyl-3-pentyl) have been prepared from the corresponding tert-alkoxytrichlorosilanes and successfully used as molecular building blocks to produce ordered siloxane-based nanomaterials. Controlled hydrolysis of the alkoxytrichlorosilanes led to the formation of crystalline powders of alkoxysilanetriols that were stable under ambient conditions. Solid-state polycondensation of the alkoxysilanetriols occurred upon heating, which led to

A novel hybrid mesoporous material functionalized with carboxy groups was synthesized by self-assembly of a novel building block consisting of a cubic siloxane unit and a long organic chain with an ester bond and the following hydrolysis of ester bonds, representing a promising approach to designing hybrid structures at both molecular and mesoscopic scales.

Siloxane-based materials have a wide range of applications. Cage-type oligosiloxanes have attracted significant attention as molecular building blocks to construct novel siloxane-based nanoporous materials with promising applications such as in catalysis and adsorption. This paper reviews recent progress in the preparation of siloxane-based nanoporous materials using alkoxy- and silanol-functionalized cage siloxanes. The arrangement of cage siloxanes units is controlled by various methods, inclu

Oriented multilayered films composed of alternating siloxane layers and organic layers were prepared from mixtures of tetramethoxysilane [Si(OMe)4] and unsaturated organotrimethoxysilane [RSi(OMe)3, where R is CH2CH(CH2)8– or CH2CH(CH2)2CHCH(CH2)4–], and the structures and macroscopic properties of the films were studied. Hydrolysis and partial condensation of the precursors led to the formation of amphiphilic organosiloxane species which self-assemble into lamellar phases. Polymerization of the