title: Self-assembly of alkyl-substituted cubic siloxane cages into ordered hybrid materials.
abstract: 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 processes. Analysis of the solid-state (29)Si MAS NMR spectra of these hybrid mesostructures confirmed that the cubic siloxane units were cross-linked to form siloxane networks. Calcination of these hybrids gave mesoporous silica, the pore diameter of which varied depending on the alkyl-chain length. We also found that the precursors that had two alkyl chains formed lamellar phases, thus confirming that the number of alkyl chains per cage had a strong influence on the mesostructures. These results expand the design possibility of novel nanohybrid and nanoporous materials through the self-assembly of well-defined oligosiloxane-based precursors.
authors.affiliation: Department of Chemical System Engineering, The University of Tokyo, Hongo-3, Bunkyo-ku, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shimojima
authors.forename: Ryota
authors.initials: R
authors.lastname: Goto
authors.forename: Norimasa
authors.initials: N
authors.lastname: Atsumi
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kuroda