Anisotropy of free-volume-hole dimensions in polymers probed by positron-annihilation spectroscopy
- 15 November 1990
- journal article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 42 (15) , 9705-9708
- https://doi.org/10.1103/physrevb.42.9705
Abstract
The structures of atomic-scale free-volume holes in stretched [poly(aryl-ether-ether-ketone)] PEEK and [poly(methyl methacrylate)] PMMA polymers were determined as a function of orientation by measuring the angular correlation of annihilation radiation from parapositronium trapped in the holes. The measured average hole diameters were found to range from 0.80±0.03 to 0.31±0.02 nm and from 0.70±0.03 to 0.42±0.02 nm, depending on orientation, in stretched PEEK and PMMA, respectively. Thus, the free-volume holes were ellipsoids with anisotropies of 2.6±0.2 and 1.7±0.2 for PEEK and PMMA, respectively.Keywords
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