Rational design of intrinsically ultramicroporous polyimides containing bridgehead-substituted triptycene for highly selective and permeable gas separation membranes

Raja Swaidan, Majed Al-Saeedi, Bader Ghanem, Eric Litwiller, Ingo Pinnau

Research output: Contribution to journalArticlepeer-review

119 Scopus citations

Abstract

Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted triptycene demonstrated the highest BET surface area reported for polyimides (840 m2 g-1) and several new highs in gas selectivity and permeability for hydrogen (1630-3980 barrers, H2/CH4 ∼ 38) and air (230-630 barrers, O 2/N2 = 5.5-5.9) separations. Two new dianhydrides bearing 9,10-diethyl- and 9,10-dipropyltriptycenes indicate that the ultramicroporosity is optimized for fast polymeric sieving with the use of short, bulky isopropyl bridgeheads and methyl-substituted diamines (TrMPD, TMPD, and TMBZ) that increase intrachain rigidity. Mechanically, the triptycene-based analogue of a spirobisindane-based polyimide exhibited 50% increases in both tensile strength at break (94 MPa) and elastic modulus (2460 MPa) with corresponding 90% lower elongations at break (6%) likely due to the ability of highly entangled spiro-based chains to unwind. To guide future polyimide design, structure/property relationships are suggested between the geometry of the contortion center, the diamine and bridgehead substituent, and the mechanical, microstructural, and gas transport properties. © 2014 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)5104-5114
Number of pages11
JournalMacromolecules
Volume47
Issue number15
DOIs
StatePublished - Jul 15 2014

ASJC Scopus subject areas

  • Materials Chemistry
  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry

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