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

J. W. Xu, M. L. Chng, T. S. Chung*, C. B. He, R. Wang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)4715-4721
Number of pages7
Issue number16
StatePublished - Jul 10 2003
Externally publishedYes


  • 6FDA-polyimide
  • Gas separation
  • Permeability

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics
  • Organic Chemistry


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