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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 62: Charged Soft Matter, Polyelectrolytes and Ionic Liquids III

CPP 62.13: Vortrag

Donnerstag, 15. März 2018, 12:45–13:00, C 243

How to tune the surface forces of PDADMA terminated polyelectrolyte multilayers — •Heba Soker Mohamad, Sven Neuber, and Christiane A. Helm — Institut für Physik, Uni. Greifswald, Felix-Hausdorff-Str. 6 17489 Greifswald

Films built from the Poly (styrenesulfonate) (PSS) and poly (diallylmethylammonium) (PDADMA) in 0.1 Mol/L NaCl are investigated. Colloid probe measurements show that PDADMA-terminated surfaces are always positively charged. They are flat if the film consists of few layers. By increasing the number of layers, steric forces due to chains protruding into solution are observed. The PDADMA chains scale as polyelectrolyte brushes and collapse at 1 M NaCl. If the top layers contain an excess of PDADMA monomers neutralized by Cl- ions, at salt concentrations larger than 1 M NaCl again brushes form. Also NaCl penetrates into the film, breaks up ionic monomer-monomer bonds and causes irreversible changes. Concluding, surface forces of polyelectrolyte multilayer can be controlled by preparation and post-preparation treatment.