Berlin 2008 – scientific programme

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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.50: Poster

Tuesday, February 26, 2008, 14:30–20:00, Poster A

Bundle Formation in Polyelectrolyte Brushes — •Jens-Uwe Günther, Heiko Ahrens, and Christiane A. Helm — Institut für Physik, Ernst-Moritz-Arndt Universität, Felix-Hausdorff-Str. 6, D-17487 Greifswald, Germany

Theoretical predictions of bundling phenomena in semiflexible polyelectrolytes in the presence of monovalent and divalent counterions are tested with X-ray grazing incidence diffraction. We use amphiphilic diblock copolymers consisting of a hydrophobic anchor and a polyelectrolyte block (PEE-PSS, PBA-PAMPS, PIB-PMMA) grafted at the air-water interface to form polyelectrolyte brushes. The brush thickness determined by X-ray reflectivity amounts to 30-50% of the contour length. In-plane peaks are observed for different kind of counterions (monovalent Cs+ and Na+, divalent Ca2+ and Sr2+ ) and different ion concentrations in the subphase. Increased salt concentration in the polyelectrolyte brush leads to a decrease in bundle length, as well as to more chains per bundle hence larger bundle diameters. These observations are consistent with a decreased electrostatic repulsion between the chains, which lead to a decreased persistence length as well as a decreased repulsion between chains.