Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 25: Polyelectrolytes
CPP 25.5: Vortrag
Mittwoch, 27. Februar 2008, 15:30–15:45, C 230
Swelling of PEM with different charge densities at solid support in humid nitrogen atmosphere: A neutron reflectometry study — •Ralf Köhler1,2, Ingo Dönch2, André Laschewsky3, Andreas Fery4, and Rumen Krastev2 — 1HMI Berlin, Abt. SF1, Berlin — 2MPI KGF, Abt. GF, Potsdam — 3Fraunhofer IAP, Abt. Wasserbasierte Systeme, Potsdam — 4Universität Bayreuth, Phys. Chemie II, Bayreuth, Germany
Polyelectrolyte Multilayers (PEM) are composites of self-assembled (layered) polyions of alternating charges. They are interesting materials for technical application and fundamental research with a high potential for appliance in medical, biotechnological and pharmaceutical purposes. NR maid be expected to be the perfect tool for measuring of swelling behaviour of PEM (here PSS/PDADMAC) because both, thickness change and water content can be obtained simultaneously. The samples were prepared in Layer-by-Layer technique (spraying) applying PDADMAC with different charge densities (100%, 89% and 75%). It was found that the water uptake is almost linear with the relative humidity of surrounding vapour. The swelling of the PEM depends nonlinearly from the water content of the multilayers. Significant dependence of the swelling and/or water uptake on the charge density was not observed on ultra-thin PEM. Further experiments were addressed to the swelling behaviour by variation of the initial PEM thickness. No intense thickness dependence was observed but a well pronounced non equal distribution of the polymer chains (respectively water uptake) normal to the surface was documented.