title: Oligomeric alkoxysilanes with cagelike hybrids as cores: designed precursors of nanohybrid materials.
abstract: Well-defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane-based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono-, di-, and triethoxychlorosilanes ((EtO)(n)Me(3-n)SiCl, n=1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups (n). When n=2 and 3, microporous xerogels (BET surface areas of 820 and 510 m(2) g(-1), respectively) were obtained, whereas a nonporous xerogel was obtained when n=1. (29)Si NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si-O-Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure-directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n=2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol-gel chemistry.
authors.affiliation: Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan, Fax: (+81) 3-5286-3199.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kuge
authors.affiliation: Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan, Fax: (+81) 3-5286-3199.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Hagiwara
authors.affiliation: Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Honcho 4-1-8, Kawaguchi-shi, Saitama, 332-0012, Japan.|Department of Chemical System Engineering, The University of Tokyo, Hongo-7, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shimojima
authors.affiliation: Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan, Fax: (+81) 3-5286-3199.|Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Nishiwaseda-2, Shinjuku-ku, Tokyo, 169-0051, Japan.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Honcho 4-1-8, Kawaguchi-shi, Saitama, 332-0012, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kuroda