Structure and morphology of propylthiol-functionalised mesoporous silicas templated by non-ionic triblock copolymers

The effect of the co-condensation of 3-mercaptopropyltriethoxysilane (MPTES) in the preparation of mesoporous silicas has been examined for levels of MPTES of 0-10 mol% (based on silicon) in reported syntheses using the block co-polymers P123 and F127. In syntheses using P123, SBA-15 (p6mm) forms with 0-5 mol% MPTES whereas addition of 7 mol% of the silane results in highly ordered Ia3¯d silica. Using F127, synthesis in the absence of MPTES gives the reported cubic Fm3m FDU-12 structure, based on the cubic close packing of surfactant micelles, whereas addition of MPTES results in the introduction of a high concentration of stacking defects in the close packing sequences and changes in particle morphology. At 5 mol% MPTES, tapered hexagonal prismatic particles with nano-domains of the hexagonally close packed structure (space group P63/mmc) are obtained. The accessible thiol contents in the members of these two series of solids have been determined using Ellman's reagent (5,5′-dithiobis-(2-nitrobenzoic acid)): values of 50-70% of the thiols incorporated in the solid have been measured as being accessible to this reactant.