ISSN:
0887-6266
Keywords:
three-component polyimides, gas permeation in
;
packing density of copolyimides
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Packing density and gas permeability of a three-component copolymide series is presented. The three-component polyimides are prepared a via “stepwise” synthesis procedure that goes through the acid anhydride terminated pre-polymer. The procedure ensures the statistical distribution of segments of the polymers. The polyimide series is composed of contrasting segments: a bulky and rigid hexafluoroisopropylidene-2,2-bis(phthalic acid anhydride)/9,9,-bis(4-aminophenyl)fluorene and a flexible hexafluoroisopropylidene-2-2-bis(phthalic acid anhydride)/2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, with varying segment ratio. Generation of additional free volume by compolymerizing two segments is observed. The permeability of six pure gases - He, H2, N2, O2, CH4, and CO2 - to the polymides showed positive deviation from the simple additivity rule of segment weight ratio reflecting the generation of free volume. However, a conflicting result between free volume fraction and gas permeability is observed, which may be due to a difference of the nature of free volume of each segment. © 1994 John Wiley & Sons, Inc.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1994.090320606
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