Existence of a Microporous Corona around the Mesopores of Silica-Based SBA-15 Materials Templated by Triblock Copolymers

Abstract

Materials showing long-range two-dimensional hexagonal order (called SBA-15 in the literature) were produced by templating a silica precursor (TEOS) with two Pluronic copolymers, EOxPOyEOx, of nearly the same x/y (0.3) ratio but different y values (x = 18, y = 60 and x = 20, y = 70, respectively). These materials were hydrothermally treated to increase the condensation of silicate species around the Pluronic aggregates and calcined to liberate the hexagonal array of mesopores. All materials, i.e., before and after hydrothermal treatment and calcination, were investigated by X-ray diffraction (XRD), and all calcined samples were further characterized by transmission electron microscopy and N2 sorption experiments. The large number and narrow width of the XRD powder diffraction lines demonstrate the good crystallographic quality of the materials. This allows us to quantitatively exploit the XRD reflection intensities and to show that simple structural models of the silica lattice cannot account for them. Th...