Regensburg 2002 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 11: Dünne Filme, Monolagen und Oberfl
ächen

CPP 11.2: Talk

Wednesday, March 13, 2002, 13:50–14:10, H38

Counterion Induced Desorption Kinetics of κ-Carrageenan in Aqueous Solution on Different Substrates — •Marc Schneider and Helmuth Möhwald — Max Planck Institut für Kolloid- und Grenzflächenforschung, 14476 Golm

We investigated the in solution well characterised polysugar κ-carrageenan at the surface. It is know that these molecules form helices dependent on the counterion and in addition networks between the molecules are promoted in dependence of the same counterion. Using the right ions this helix and network formation is reversible. Most of the work using SFM methods was done in alcoholic solutions to reduce the forces applied from the tip. The imaging in aqueous solution needs a stronger fixing to the surface. Therefore, different modifications with different molecular structure and charge density (3-aminopropyldimethylethoxysilane (APDMES) and polyethyleneimine (PEI)) were used. What we observe is a stable network formation on the surface with potassium as counterion. The exchange of the ions from potassium to lithium, which should induce a change in conformation leads to desorption of the molecules. The desorption shows a strong time dependence with varying the layer that promotes the fixation on the substrate. The kinetic of the desorption process can be investigated by force measurements and in situ mass measurements.