Wet-Chemical Analysis of Surface Concentration of Accessible Groups on Different Amino-Functionalized Mesoporous SBA-15 Silicas

Abstract

Surface functionalization is one of the key steps toward the utilization of mesoporous materials in different applications. In this study, we characterized amino-functionalized mesoporous SBA-15 silicas that have been prepared by different means; co-condensation, post-grafting of amino-silanes, and surface hyperbranching polymerization of poly(ethylene imine). Special focus is put on the accessibility of the introduced function. The materials are thoroughly characterized both by structural and by surface chemical means. We generally observe a good agreement between the C-value derived from BET surface area analysis, the number of accessible amine groups determined by quantitative imine reaction in solution, and zeta-potential measurements. Furthermore, indirect information about differences in the number of amine groups present on the outside surface of the particles can also be obtained. Our results clearly show that there are large differences between the availability of the amine function for materials...