Unusual temperature dependence of the positron lifetime in a polymer of intrinsic microporosity

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 acce...

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Bibliographic Details
Published in:Physica status solidi. PSS-RRL. Rapid research letters 2007-10, Vol.1 (5), p.190-192
Main Authors: Lima de Miranda, Rodrigo, Kruse, Jan, Rätzke, Klaus, Faupel, Franz, Fritsch, Detlev, Abetz, Volker, Budd, Peter M., Selbie, James D., McKeown, Neil B., Ghanem, Bader S.
Format: Article
Language:English
Subjects:
61.41.+e
65.60.+a
71.60.+z
78.70.Bj
81.05.Lg
81.05.Ru
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Exact sciences and technology
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
Other interactions of matter with particles and radiation
Physics
Positron annihilation
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Summary: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) The Letter presents the temperature dependence of positron annihilation lifetime spectrocopy (PALS) in polymers of intrinsic microporosity in the range from 143 to 523 K. The lifetime, which is a measure for the free volume, does not follow the linear macroscopic thermal expansion, but exhibits a non‐monotonous behaviour. Possible explanations for this deviation are discussed.
ISSN:1862-6254
1862-6270
DOI:10.1002/pssr.200701116