Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 5: Interfaces
CPP 5.7: Vortrag
Montag, 23. März 2009, 12:00–12:15, ZEU 160
Free volume distribution at a polymer-solid interface investigated by a slow positron beam — •Stephan Harms1, Klaus Rätzke1, Vladimir Zaporojtchenko1, Franz Faupel1, Werner Egger2, and Peter Sperr2 — 1Technische Fakultät der CAU, Lehrstuhl für Materialverbunde, Kaiserstr. 2, 24143 Kiel, Germany — 2Universität der Bundeswehr München, Neubiberg, Germany and FRM II München
Polymer-solid contacts are important for many applications such as adhesion, coating and nanocomposites. Mechanical and permeability properties of polymers are strongly connected to the free volume cavity size and fractions, which might be different at the boundary layer. Positron annihilation lifetime spectroscopy is a widely accepted experimental technique to study the free volume in polymers. The ortho-positronium lifetime is directly connected to the mean free volume size. A tunable low-energy positron beam allows us to measure the free volume as a function of the depth on a nm scale. For the first time we investigated several Teflon AF2400/silicon interfaces at different positron beam energies which corresponds to various depths from surface to interface. By this we obtain information about free volume, the thickness of the interphase region and changes in the free volume in this area. First evaluation shows a decrease in free volume fraction at the interface while the size of the cavities stays constant. We acknowledge the financial support by the DFG within the priority program (SPP) 1369 (Ra 796/5-1).