Dresden 2006 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 22: Thin film deposition and process characterization II
DS 22.5: Vortrag
Donnerstag, 30. März 2006, 15:00–15:15, GER 38
Influence of salt ions on the structure of polyelectrolyte multilayers — •Christof Ecker1, John E. Wong2, Pantea Nazaran3, and Regine v. Klitzing1 — 1Christian-Albrechts-Universität Kiel, Institut für Physikalische Chemie, Ludewig-Meyn-Str. 8, 24118 Kiel — 2RWTH Aachen, Institut für Physikalische Chemie, Landoltweg 2, 52056 Aachen — 3Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Wissenschaftspark Golm, 14424 Potsdam
A polyelectrolyte multilayer is grown by dipping the substrate alternately into solutions of polycations and polyanions. At each step a polyelectrolyte layer adsorbs from solution onto the surface.
We investigated how the addition of monovalent salt to the solutions of polyanions (PSS) and polycations (PAH or PDADMAC) influences the structure of such layers. We found that the layer thickness always increases with salt concentration. We explain this by the more compact conformation in solution. Further, we found a strong dependence on the type of salt. Films built-up with NaBr are about five times thicker compared to those prepared with NaF. The mobility of the polymers chains within the multilayer film was measured using FRAP (Fluorescence Recovery After Photo bleaching). We found the mobility for films prepared under NaBr conditions to be large compared to films prepared with NaCl and similar to films prepared from a less charged copolymer. This indicates that Br- ions are embedded within the film reducing the charge of the polycations extrinsically and whereas Cl- ions are not. We further performed calorimetric experiments to quantify the interaction between polyelectrolyte and salt ions.