title: Molecularly ordered inorganic frameworks in layered silicate surfactant mesophases.
abstract: Self-assembled lamellar silica-surfactant mesophase composites have been prepared with crystal-like ordering in the silica frameworks using a variety of cationic surfactant species under hydrothermal conditions. These materials represent the first mesoscopically ordered composites that have been directly synthesized with structure-directing surfactants yielding highly ordered inorganic frameworks. One-dimensional solid-state 29Si NMR spectra, X-ray diffraction patterns, and infrared spectra show the progression of molecular organization in the self-assembled mesophases from structures with initially amorphous silica networks into sheets with very high degrees of molecular order. The silicate sheets appear to be two-dimensional crystals, whose structures and rates of formation depend strongly on the charge density of the cationic surfactant headgroups. Two-dimensional solid-state heteronuclear and homonuclear NMR measurements show the molecular proximities of the silica framework sites to the structure-directing surfactant molecules and establish local Si-O-Si bonding connectivities in these materials.
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Christiansen
authors.forename: D
authors.initials: D
authors.lastname: Zhao
authors.forename: M T
authors.initials: MT
authors.lastname: Janicke
authors.forename: C C
authors.initials: CC
authors.lastname: Landry
authors.forename: G D
authors.initials: GD
authors.lastname: Stucky
authors.forename: B F
authors.initials: BF
authors.lastname: Chmelka