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Sorption of small molecules in various polycarbonates and Kapton-H

✍ Scribed by A. Grüger; P. Gotthardt; M. Pönitsch; H. G. Brion; R. Kirchheim

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
258 KB
Volume
36
Category
Article
ISSN
0887-6266

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✦ Synopsis

Pressure-composition isotherms were determined at 20ЊC for CO 2 in Kapton and various substituted polycarbonates and for H 2 O, Ar, N 2 , CH 4 , and acetone in bisphenol-A-polycarbonate. The isotherms are described by two parameters an average free energy of sorption and a width of a Gaussian distribution of free sorption energies. Within the framework of a recent model these parameters can be calculated assuming an elastic distortion of the polymer caused by the incorporation of solute atoms in preexisting holes. By comparing experimental values with predictions of the model the experimental width of the free energy distribution is only 30% smaller than the theoretical one. Functional relationships are obeyed between the sorption parameters on the one hand and glass transition temperature, average hole volume, and molecular volume of the solute on the other hand. Deviations occur for larger molecules like acetone and ethylene which are attributed to a viscoelastic distortion of the polymer. Comparing free energies of solution for the rubbery and glassy state of the polymer reveals more negative values for the glassy polymers despite their extra elastic distortion energy. This discrepancy is overcome by taking into account that the occupied volume has to be re-formed in the case of the rubbery or liquid polymer.

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