Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 7: Interfaces and Thin Films II

CPP 7.11: Talk

Monday, March 14, 2011, 16:45–17:00, ZEU 114

Laser-assisted atom probe tomography of polyelectrolyte multilayers — •Andreas Stoffers and Guido Schmitz — Institut für Materialphysik, Westf. Wilhelms-Universität, Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany

Atom probe tomography (APT) is a well established tool for analyzing metals at an atomic scale. In order to explore the possibilities of analyzing polymer materials by Pulsed-laser atom probe tomography (PLAP), we have chosen the model case of polyelectrolyte multilayers (PEM). PEMs are adsorbed step by step as a multilayer of poly-anions and poly-cations at the apex of sharp gold tips. This self-assembly is driven by electrostatic forces, where every adsorbed layer induces a charge inversion of the surface. Macroscopic charge neutrality requires an exact 1:1 stoichiometry of polycation and polyanion charges or the presence of counterions within the layer. The presence of counterions in PEMs is controversially discussed and laser-assisted atom probe tomography seems to be an ideal tool to answer this question. By means of laser-assistance it is indeed possible to chemically analyze multilayers of poly(acrylic acid), poly(diallyl dimethyl-ammonium chloride), poly(styrene sulfonate) and poly(allylamine hydrochloride). In all cases the mass spectra are complex, characterized by peaks of multiple fractions of different molecular mass. Different polymer-types might be distinguished based on the intensity ratio between characteristic mass peaks. The proven amount of counterions is obviously negligible. In addition, a 3D reconstruction of a self assembled monolayer (1H,1H,2H,2H-Perfluorodecanethiol) will be presented.