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B. Feichtenschlager, G. Kickelbick, T. Koch, S. Pabisch, H. Peterlik, M Sajjad:
"Chemical tailoring of nanoparticle surfaces: How do nanoscopic properties affect macroscopic properties in inorganic-organic nanocomposites?";
Poster: 3^rd EuCheMS Chemistry Congress, Nürnberg; 29.08.2010 - 02.09.2010; in: "Programme - Abstracts", (2010), 1 S.

The interface compatibility beetween inorganic and organic components in polymer nanocomposites was increased using capping agent molecules consisiting of a anchor group, inert space and end group. This results in a better dispersibility of the inorganic nanobuilding blocks in the organic matrix and in addition molecules at the surface of the inorganic phase may also contain functional groups allowing a covalent linkage to the polymer during in situ polymerization. In this work we investigated the influence of spacer chain nature and functional end group of the nanoparticle capping. Commonly used long alkyl chain spacers tend to form well ordered self-assembled monolayers on the surface of the nanobuilding blocks. This can lead to strong particle aggregations via interparticle bilayer formation. This phenomenon can be overcome by mixing capping agents or the use of non alky-chains groups. Therefore we studied PEO- and PDMS-grafted nanoparticles as building blocks. Functional end groups of the capping agents were varied to demonstrate the influence of their physical nature on the homogeneity of the dispersion and also the impact of a copolymerization of the end group with the polymer backbone. Zirconia nanoparticles (22 nm diameter) and silica particles with various diameters (9 nm to 600 nm) were used as model systems. The capping agents contained phosphonic acids anchor groups for the zirconia and trialkoxysilanes for the silica systems. The dispersibility of the modified particles in organic media was investigated by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) experiments. The particles were used as building blocks for the preparation of nanocomposites with poly(methyl methacrylate), polystyrene or epoxy resin formulations as polymer matrix. The chemical parameters changed on the molecular scale had also an impact on macroscopic properties. Thus, correlations between particle size and mechanical toughness as well as between spacer nature and homogeneity were observed for epoxy resin nanocomposites. Thermomechanical properties of the thermoplast model systems increased using proper copolymerizable endcapping.

nanoparticles, nanocomposites, surface modification, hybrid materials, zirconium oxide, phosphonic acids, small angle x-ray scattering

Projektleitung Guido Kickelbick:
Chemisch massgeschneiderte Grenzflächen in Nanokompositen