Regensburg 2007 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 15: Diffusion and Transport Processes
CPP 15.2: Vortrag
Dienstag, 27. März 2007, 14:45–15:00, H47
Temperature Dependence of Positron Lifetime in a Polymer of Intrinsic Microporosity — •Klaus Rätzke1, Rodrigo Lima De Miranda1, Jan Kruse1, Franz Faupel1, Detlev Fritsch2, Volker Abetz2, Peter Budd3, James Selbie3, Neil McKeown4, and Bader Ghanem4 — 1Univ. Kiel, Materialverbunde, Kaiserstr. 2, 24143 Kiel — 2Institut für Polymerforschung, GKSS, Max-Planck-Strasse 1, 21502 Geesthacht — 3School of Chemistry, The University of Manchester, Manchester M13 9PL, UK. — 44School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK.
The performance of polymeric membranes for gas separation is mainly determined by the free volume. Polymers of intrinsic microporosity are interesting candidates for state of the art gas separation membranes due to the high abundance of accessible free volume. Positron annihilation lifetime spectroscopy is a generally accepted technique for investigation of free volume in polymers where the orthopositronium lifetime is directly connected to the mean free volume size. We performed measurements of the temperature dependence of the positron lifetime in a polymer of intrinsic microporosity (PIM-7) in the range from 143 to 523 K. The mean value of the free volume calculated from the ortho-positronium life time (~5 ns) is in the range of typical values for high free volume membrane polymers (V = 0,47 nm^3). However, the temperature dependence of the positronium-lifetime is non-monotonous. Comparison with thermal expansion measurements will be made and a possible explanation of this unexpected behavior given.