Chemistry of inorganic-organic hybrid materials
Research in the group of Ulrich Schubert (US) is focused on the development of inorganic-organic hybrid materials, especially sol-gel materials and cluster-reinforced polymers, starting from a thorough understanding of the chemical fundamentals. An essential part of the work is devoted to the rational synthesis of molecular or nanoscale building blocks which are then assembled in a controlled manner to result in solid materials. The US group is not only dealing with bottom-up syntheses of new materials, but pays special attention to the question how the chemical composition and structure of the precursors influence structure and properties of the derived materials.
Methodically, work includes the wet chemical synthesis of the materials, mainly oxide-based materials, starting from molecular precursors, and their characterization by a combination of physical methods (IR and UV spectroscopy, XRD, SAXS, thermal analysis, surface and pore analysis, NMR, etc.). The combination of different characterization methods, which is a requirement for the characterization of non- or semi-crystalline materials, is a key element in the training of PhD students in this area. Since many groups in Solids4Fun are dealing with metal oxides in one way or the other (e.g., Günther Rupprechter, Jürgen Fleig, Karsten Held, Peter Blaha, Silke Bühler-Paschen, Ulrike Diebold) many collaborations are possible (some are already going on).
Part of the research of the US group is devoted to synthesizing new precursors for sol-gel processing and the understanding of their hydrolysis and condensation reactions. Examples include the development of organically modified metal alkoxide precursors and identification of their primary hydrolysis products, or investigation of the hydrolytic polycondensation of two-component precursor systems. Organically modified metal alkoxide precursors were applied for the preparation of new types of sol-gel materials, such as organically modified silica aerogels, heterogenized metal complex catalysts, sol-gel coatings for various applications, or nanocomposites in which nm-sized metal oxide or metal particles are embedded in an amorphous metal oxide matrix.
The US group has also developed an approach to use metal oxide clusters with polymerizable organic ligands together with organic co-monomers in various polymerization reactions. Polymers with cluster cross-links are thus obtained and have interesting materials properties. Concomitant with the development of the polymers and the investigation of their materials properties, the (structural) chemistry of the clusters was also investigated and important insight was obtained, e.g. on ligand exchange processes, rearrangements or ligand dynamics.