Berlin 2001 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 18: Poster: Polymer Blends, Heterogeneous Systems, Colloids and Nanoparticles, Interfaces, Polyelectrolytes
CPP 18.34: Poster
Wednesday, April 4, 2001, 12:30–15:00, AT1
Adsorption of Polyelectrolyte Molecules on a Molecular Scale — •M. Schneider1, G. Papastavrou2, M. Zhu1, S. Akari1, H. Möhwald1, H. Ahrens2, C.A. Helm2, A. Pfau3, Y. Thomann3, and W. Schrepp3 — 1MPI für Kolloid- und Grenzflächen Physik, 124424 Golm — 2Universität Greifswald, Angewandte Physik, 17487 Greifswald — 3BASF AG, ZKM/O - J542, Ludwigshafen
We want to image adsorbed polyelectrolyte molecules with the AFM in aqueous solutions under various pH- and salt conditions. For that end, it is necessary to tune both surface energy and surface charge within a wide range. Therefore, Alkyl Thiols with various end groups (-OH, COOH, NH2, -CH3) were synthesized. The tip modification was verified by measuring the long range interaction forces and the adhesion between tip and various substrates, some of them laterally structured. Do determine and eventually control the polyelectrolyte conformation, x-ray reflectrometry on fluid substrates was performed. Usually, the polyelectrolyte (poly styrene sulfonate) adsorbs in a flat conformation, only with low surface charge and high salt (1 M) a diffuse extended layer was observed. To avoid relocation of the adsorbed polymer, the interaction forces tip/polymer and tip/substrate have to be tuned carefully. For that end, force-distance curves between surface modified silica spheres and substrates were measured. It was found that the pulsed force mode was most suitable to image single, flatly adsorbed polyelectrolyte molecules (poly (styrene sulfonate) and poly (ethyl imine)) on solid substrates.