Berlin 2001 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 14: Self Assembled Layered Systems
CPP 14.4: Talk
Thursday, April 5, 2001, 16:45–17:05, 112
Hydration of Polyelectrolyte Multilayer Assemblies investigated by Water T2 Relaxation — •Monika Schönhoff and Bernd Schwarz — Max-Planck Institute of Colloids and Interfaces, D-14424 Potsdam/Golm
The adsorption of polyelectrolytes to charged surfaces can be applied to build up multilayers of alternatingly charged polyelectrolytes by self-assembly. Here, multilayers of PSS/PAH are adsorbed to colloidal particles to investigate the hydration by water 1H relaxation rates R2 determined in a CPMG experiment. Due to fast exchange between free water and hydration water of the multilayer assembly, R2 is an averaged quantity. The change in R2 due to the adsorption of each additional layer, DeltaR2, is monitored. With the adsorption of subsequent layers of alternating charge, an alternating behaviour of DeltaR2 is observed, since an increase occurs on adsorption of a positive layer, and a decrease on adsorption of a negative layer. The changes in hydration due to monolayer adsorption are furthermore strongly increasing with the number of precoated layers, and can be attributed to an influence of the electric potential of the outer layer on the multilayer system: A positive surface charge leads to a larger fraction of immobilised protons within the multilayers, while due to a negative surface charge deswelling occurs. These effects can arise from not compensated charges in the multilayer assembly or a change of the dissociation equilibrium of PAH within the multilayers.