Relation of gas-transport parameters of amorphous glassy polymers to their free volume: Positron annihilation study |
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Authors: | V. E. Ryzhikh A. Yu. Alent’ev Yu. P. Yampol’skii |
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Affiliation: | 19560. A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskii pr. 29, Moscow, 119991, Russia
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Abstract: | Correlations of transport parameters (diffusion coefficients D and permeabilities P of gases) and thermodynamic parameters (solubility coefficients S and parameters C′ H of sorption isotherms) with the sizes of free-volume elements, v h, as estimated via positron annihilation lifetime spectroscopy are analyzed for the first time on the basis of the data array obtained for glassy polymers. Correlations of logD and logP with 1/v h that agree with the free-volume model under the condition of a weak change in the concentration of free-volume elements in different polymers are ascertained. Certain deviations from linear correlations with 1/v h for polymers with high free volumes are interpreted as evidence that the connectivity (openness) of pores increases with the sizes of free-volume elements. For solubility coefficients and Langmuir parameters of sorption capacity C′ H , good linear correlations with the value of v h are demonstrated. |
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