Permeability of polyimides derived from non-coplanar diamines and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride

A series of polyimides including a non-coplanar moiety were synthesized in order to investigate the effect on gas permeability and selectivity. The gas permeation properties of He, H2, O2, N2, CH4 and CO2 were measured using a constant-volume method. Only 6FDA-terphenyl consisting of laterally attac...

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Bibliographic Details
Published in:Polymer (Guilford) 2003-07, Vol.44 (16), p.4715-4721
Main Authors: Xu, J.W., Chng, M.L., Chung, T.S., He, C.B., Wang, R.
Format: Article
Language:English
Subjects:
6FDA-polyimide
Applied sciences
Exact sciences and technology
Gas separation
Miscellaneous
Organic polymers
Permeability
Physicochemistry of polymers
Properties and characterization
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Summary:A series of polyimides including a non-coplanar moiety were synthesized in order to investigate the effect on gas permeability and selectivity. The gas permeation properties of He, H2, O2, N2, CH4 and CO2 were measured using a constant-volume method. Only 6FDA-terphenyl consisting of laterally attached phenyl groups shows a substantial increase because its terphenyl moiety is a rigid structure with a high aspect ratio. The order of permeability increase from 6FDA-phenyl to 6FDA-terphenyl is consistent with the calculated fraction free volume and measured permittivity. It is observed that the most gain in permeability for 6FDA-terphenyl polyimide arises from the enhancement in apparent diffusion coefficient, while the permeability increase for 6FDA-biphenyl is mainly due to the increase in solubility. A relationship of diffusivity vs. gas penetrant size as well as gas solubility vs. critical temperature of gas penetrant was also investigated.
ISSN:0032-3861
1873-2291
DOI:10.1016/S0032-3861(03)00430-0