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CPP: Chemische Physik und Polymerphysik
CPP 11: Dünne Filme, Monolagen und Oberfl
ächen
CPP 11.1: Vortrag
Mittwoch, 13. März 2002, 13:30–13:50, H38
Adsorption and Hydration of Polyelectrolyte Multilayer systems monitored by NMR T2 Relaxation of the solvent. — •Bernd Schwarz and Monika Schönhoff — Max-Planck Institute of Colloids and Interfaces, D-14424 Potsdam/Golm, Germany
The adsorption of polyelectrolytes to charged colloidal particles is applied to build up self-assembled multilayers of alternatingly charged polyelctrolytes. Multilayers of PAH/PSS and PDADMAC/PSS are adsorbed to colloidal particles to investigate their adsorption and hydration by water 1H and 2H NMR relaxation rates R2. Changes in the relaxation rate R2 due to the adsorption of each additional layer is monitored.
Adsorbing a subsequent layer of alternating charge an increasing zigzag course (odd/even effect) of R2 is very pronounced for PAH/PSS and barely detectable for PDADMAC/PSS. This effect is switched only by the electrical potential of the outer layer, not by the electrolyte strength of the polyelectrolyte and is an integrated effect of all layers. A positive surface charge leads to a larger fraction of immobilized protons within the multilayers - a swelling of the multilayers occurs, while due to a negative surface charge deswelling occurs. The effects arise from different amounts of immobilized water within the multilayers in dependency of increasing zigzag course. R2 is tuneable with pH. Multilayers of PDADMAC/PSS show an equal dependency on pH independent of the electrical potential of the outer layer. Whereas multilayers of PAH/PSS show between pH 6 and 9 opposite dependencies on pH depending on the electrical potential of the outer layer.