Dendritic, Nanosized Building Block for Siloxane-Based Materials: A Spherosilicate Dendrimer

Authors

  • Kazufumi Kawahara,

    1. Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo 169-8555 (Japan), Fax: (+81) 3-5286-3199
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  • Dr. Yoshiaki Hagiwara,

    1. Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo 169-8555 (Japan), Fax: (+81) 3-5286-3199
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  • Prof. Kazuyuki Kuroda

    Corresponding author
    1. Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo 169-8555 (Japan), Fax: (+81) 3-5286-3199
    2. Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Nishiwaseda-2, Shinjuku-ku, Tokyo, 169-0051 (Japan)
    • Department of Applied Chemistry, Waseda University, Ohkubo-3, Shinjuku-ku, Tokyo 169-8555 (Japan), Fax: (+81) 3-5286-3199
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Abstract

A spherosilicate dendrimer (DMS-1) with closely spaced reaction sites (Si[BOND]H groups) on the dendrimer surface has been synthesized by stepwise silylation of double-four-ring silicate with chlorotriethoxysilane (ClSi(OEt)3) and subsequently with chlorodimethylsilane (ClSiHMe2). DMS-1 consists of a maximum of 40 Si atoms in the interior frameworks and 24 reactive Si[BOND]H groups on the surface. Because DMS-1 is spherical and about 1.5 nm in diameter, it can be regarded as the smallest well-defined silica-based nanoparticle. DMS-1 also forms molecular crystals and is soluble in typical organic solvents. A molecularly ordered silica-based hybrid can be prepared by heating a cast film of DMS-1 at 180 °C for 5 days. The surface of DMS-1 can be modified by hydrosilylation with 1-hexadecene, triethoxyvinylsilane, and allylic-terminated tetraethylene glycol monomethyl ether. More than 20 Si[BOND]H groups out of 24 react with these reagents. The solubilities of the products depend on the modification. DMS-1 is not only a building block for nanohybrids, but also the smallest and most precisely designed siloxane-based nanoparticle.

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