Thermally cross-linked diaminophenylindane (DAPI) containing polyimides for membrane based gas separations

Michelle E. Dose, Malgorzata Chwatko, Ivo Hubacek, Nathaniel A. Lynd, Donald R. Paul, Benny D. Freeman

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


This study aims to expand structure-property relationships of diaminophenylindane (DAPI)-containing polyimides and the influence of thermal cross-linking on gas transport properties of such materials. A polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride (6FDA), DAPI, and diaminobenzoic acid (DABA) in a molar ratio of 0.5/0.33/0.17, 6FDA0.5-DAPI0.33/DABA0.17, was crosslinked by thermal decarboxylation. After cross-linking, pure gas permeability of 6FDA0.5-DAPI0.33/DABA0.17 increased with increased cross-linking time; gas permeability increased by about 30% after cross-linking at 353 °C for 40 min. This increase in permeability correlated with an increase in d-spacing measured by wide angle x-ray scattering, suggesting an increase in inter-chain spacing upon cross-linking. Minimal changes in O2/N2 and N2/CH4 selectivities occurred with increased thermal cross-linking time for 6FDA0.5-DAPI0.33/DABA0.17. However, CO2/CH4 and C2H4/C2H6 pure gas selectivities increased with thermal treatment, suggesting a potential narrowing of free volume distribution.

Original languageEnglish
Pages (from-to)16-26
Number of pages11
StatePublished - Jan 14 2019

Bibliographical note

Funding Information:
This material is based upon work supported in part by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1610403 . The authors gratefully acknowledge partial support from the Division of Chemical Sciences, Geosciences, and Biosciences , Office of Basic Energy Sciences of the U.S. Department of Energy (DOE), USA through Grant DE-FG02-02ER15362 for the synthesis and characterization studies. Additionally, BDF's work in preparing this manuscript was supported in part by the National Science Foundation under Cooperative Agreement No. EEC-1647722 . Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. NAL and MC thank the National Science Foundation for partial support of this research (CBET-1706968), specifically for the NMR and molecular weight analysis. Use of the 13 C CP/TOSS solid-state NMR instrumentation is funded in part by NSF grant No. CHE-1623211. The authors acknowledge Steve Swinnea and Steve Sorey from The University of Texas at Austin for their assistance in measuring and interpreting WAXS and SS-NMR results, respectively.

Publisher Copyright:
© 2018 Elsevier Ltd


  • Cross-linking
  • Diaminophenylindane (DAPI)
  • Polyimides
  • Pure gas permeability
  • Thermal decarboxylation

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry


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