Molecular Insights On Meso- and Macroscale Properties of Self-Assembled Organic-Inorganic Materials

Currently, mesostructured solids are sought with improved mechanical, adsorption, catalytic, and/or transport properties, though these are difficult to achieve using conventional surfactant-directed inorganic oxide materials. Increasingly, greater compositional diversity is being examined to modify material properties, although species interactions and self-assembly within more complicated mixtures are not well understood and are difficult to control. Establishing the local, mesoscopic, and macroscopic compositions and structures of such materials are complicated by the absence of long-range molecular order and the heterogeneous, non-equilibrium, and multi-component characters of these hybrid materials. Mesostructured organosilicas represent an important class of hybrid solids, in which organic moieties may be either covalently cross-linked with or physically intercalated throughout otherwise siliceous frameworks. 2D solid-state nuclear magnetic resonance (NMR) spectroscopy, in conjunction with small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and bulk measurements, enable molecular compositions and framework structures to be correlated with mesoscale and macroscopic properties. These analyses establish that the organic content, type of organic moieties, and nature of organic-silica interactions within the framework are important to the self-assembly, mesostructural ordering, and bulk adsorption or mechanical properties. The results can be understood in the context of a rational design strategy for syntheses of self-assembled organosilicas with tunable material properties.