Unusual temperature dependence of the positron lifetime in a polymer of intrinsic microporosity |
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| Authors: | Rodrigo Lima de Miranda Jan Kruse Klaus Rätzke Franz Faupel Detlev Fritsch Volker Abetz Peter M Budd James D Selbie Neil B McKeown Bader S Ghanem |
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| Institution: | 1. Technische Fakult?t der Christian‐Albrechts‐Universit?t, Lehrstuhl für Materialverbunde, Kaiserstr. 2, 24143 Kiel, Germany;2. Institut für Polymerforschung, GKSS‐Forschungszentrum Geesthacht GmbH, Max‐Planck‐Stra?e 1, 21502 Geesthacht, Germany;3. School of Chemistry, The University of Manchester, Manchester M13 9PL, UK;4. School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK |
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| Abstract: | The performance of polymeric membranes for gas separation is mainly determined by the free volume. Polymers of intrinsic microporosity are interesting due to the high abundance of accessible free volume. We performed measurements of the temperature dependence of the positron lifetime, generally accepted for investigation of free volume, in two polymers of intrinsic microporosity (PIM‐1 and PIM‐7) in the range from 143 to 523 K. The mean value of the free volume calculated from the ortho‐positronium lifetime is in the range of typical values for high free volume polymers. However, the temperature dependence of the local free volume is non‐monotonous in contrast to the macroscopic thermal expansion. The explanation is linked to the spirocenters in the polymer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) |
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| Keywords: | 61 41 +e 65 60 +a 71 60 +z 78 70 Bj 81 05 Lg 81 05 Ru |
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