Regensburg 2007 – wissenschaftliches Programm

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SYPE: Symposium Polyelectrolytes

SYPE 2: Polyelectrolytes I

SYPE 2.2: Vortrag

Donnerstag, 29. März 2007, 14:30–14:45, H37

Pore size distribution in polyelectrolyte multilayers determined by cryoporometry — •Fabiàn Vaca Chàvez and Monika Schönhoff — Institut für Physikalische Chemie, WWU Münster, Germany

Permeability and porosity of polyelectrolyte multilayers (PEM) are properties of major interest, as they are crucial for applications in encapsulation, controlled release and membrane separation. In the current work the first pore size distribution of PEM in samples consisting of silica particles coated with poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) is presented. To this end, the Nuclear Magnetic Resonance (NMR) cryoporometry technique was applied. NMR cryoporometry has been successfully applied to various porous systems and, in our approach, we consider polyelectrolyte multilayers as a porous material, where the hydration water can freeze in dependence on the size of water pores. The proton NMR signal of liquid water is analyzed assuming a log normal distribution of motional correlation times. From our results, is possible to determine the size of water sites in the layers to around 1 nm. In addition, a slight variation with the number of layers is found. The average pore size agrees with cut-off sizes found in permeation experiments.