Regensburg 2004 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 4: Dynamics of Molecular Systems
CPP 4.3: Vortrag
Montag, 8. März 2004, 11:45–12:00, H 38
Free volume in polymeric membranes: comparison of positron annihilation lifetime spectroscopy and evaluation of MD simulations — •Jan Kruse1, Jörn Kanzow1, Klaus Rätzke1, Franz Faupel1, Matthias Heuchel2, and Dieter Hofmann2 — 1University of Kiel, Kaiserstr.2, 24143 Kiel — 2GKSS-Research Center, Kantstr. 55, 14513 Teltow
Gas separation by membranes is important for many technical applications. The amount and distribution of free volumes in polymeric membranes significantly determines the transport and separation properties. In the present work these free volume characteristics were determined directly from MD simulations via a new method [1,2]. Here a No-dqtracer atomNo-dq probes the simulation cell to determine the unoccupied volume. On the other hand the positron annihilation lifetime spectroscopy was used to determine the average size of free volume cavities via a well established correlation between lifetime and size. Characteristic results for polyimides will be presented, comparison of both methods will be made, and limitations of the standard model for the evolution of the positron lifetime data will be discussed.
[1] E. Schmidtke, K. Günther-Schade, D. Hofmann, F. Faupel, J. Mol. Graphics and Modelling, accepted. [2] C. Nagel, E. Schmidtke, K. Günther-Schade, D. Hofmann, D. Fritsch, T. Strunskus, F. Faupel, Macromolecules, 33, 2242 (2000).