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Some remarks on the relation between free-volume fractions and ortho-positronium lifetimes in amorphous polymers |
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| Authors: | Frans H J Maurer Marcus Schmidt |
| Institution: | a Department of Polymer Science and Engineering, Lund Institute of Technology, Center for Chemistry and Chemical Engineering, Lund University, SE-221 00 Lund, Sweden b Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden |
| Abstract: | Unique information about the properties of free-volume sites in polymers is gained from Positron Annihilation Lifetime (PAL) measurements. After calibration with data from other techniques the method may be used to determine free-volume fractions. From pressure–volume–temperature (PVT) and PAL (ortho-Ps lifetime τ3) data, measured on identical amorphous poly(methyl methacrylate) (PMMA) samples with controlled thermal histories, we find a linear relationship between free-volume fractions, derived from PVT measurements, the Simha–Somcynsky equation-of-state theory and the mean subnanometer free-volume size both below and above the glass transition temperature. |
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