Free volume dilatation in polymers by ortho-positronium

P. Winberg, Morten Mostgaard Eldrup, F.H.J. Maurer

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The possibility of positronium induced free volume cavity expansion in some polymers above the glass transition temperature was investigated using experimental positron annihilation lifetime data from the literature for polydimethylsiloxane, polyisobutylene, and polybutadiene as function of temperature.
The results suggest that free volume sites can expand towards an equilibrium size, determined as the equilibrium Ps-bubble size defined earlier for low-molecular-weight liquids. The expansion can be explained by the increase of molecular mobility and hence decrease of relaxation times, which at the higher temperatures approach the o-Ps lifetimes. Nanoscale viscosities were estimated using Navier-Stokes equation and were found to be several orders of magnitude lower than the macroscopic viscosity at the same temperature. © 2012 American Institute of Physics.
Original languageEnglish
JournalJournal of Chemical Physics
Pages (from-to)244902
Number of pages7
Publication statusPublished - 2012

Bibliographical note

Copyright (2012) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Chemical Physics / Volume 136 and may be found at


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