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B. Feichtenschlager, G. Kickelbick, T. Koch, S. Pabisch, H. Peterlik, M Sajjad:
"Inorganic-Organic Nanocomposites: Chemical Tailoring of Nanoparticle Surfaces for Optimum Homogeneity";
Talk: Minisymposium: From Molecules to Materials, Saarbrücken, Deutschland; 2009-09-10 - 2009-09-11; in: "From Molecules to Materials", (2009).

The compatibility of the inorganic phase and the organic matrix at the interface in polymer nanocomposite materials is increased using capping agents resulting in a better dispersibility of the inorganic nanobuilding blocks in an organic matrix. In addition to the surface-adaption the capping agent may also contain functional groups allowing a covalent linkage to the polymer during in situ polymerization. Many reports in literature describe the use of compounds consisting of long alkyl chains as capping agents. However, such molecules tend to form well ordered self-assembled monolayers, on the surface of the nanobuilding blocks. In some cases this can lead to a decrease in dispersibility due to interparticle aggregation phenomena.
In this work two different approaches to solve this problem were used: (i) mixing of different coupling agents which break the ordering phenomena on the surface of the particles and (ii) the use of different molecular structures such as polyethyleneglycol chains or flexible PDMS chains.
Zirconia nanoparticles (22 nm equivalent diameter) and silica particles with various diameters prepared by the Stoeber process, both with a very uniform size-distribution were used as model systems to prove these hypotheses. The capping agents contained phosphonic acids anchor groups for thezirconia and trialkoxysilanes for the silica systems. The organic functionalities attached to these anchor groups were systematically varied and ordering phenomena at the particle surface were analyzed via infrared spectroscopy studies (IR). 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.

Project Head Guido Kickelbick:
Chemisch massgeschneiderte Grenzflächen in Nanokompositen