Aliphatic/aromatic polyimide ionomers as a proton conductive membrane for fuel cell applications

Naoki Asano, Makoto Aoki, Shinsuke Suzuki, Kenji Miyatake, Hiroyuki Uchida, Masahiro Watanabe*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

174 Citations (Scopus)


To produce a proton conductive and durable polymer electrolyte membrane for fuel cell applications, a series of sulfonated polyimide ionomers containing aliphatic groups both in the main and in the side chains have been synthesized. The title polyimide ionomers 1 with the ion exchange capacity of 1.78-2.33 mequiv/g were obtained by a typical polycondensation reaction as transparent, ductile, and flexible membranes. The proton conductivity of 1 was slightly lower than that of the perfluorinated ionomer (Nafion) below 100 °C, but comparable at higher temperature and 100% RH. The highest conductivity of 0.18 S cm-1 was obtained for 1 at 140 °C. Ionomer 1 with high IEC and branched chemical structure exhibited improved proton conducting behavior without sacrificing membrane stability. Microscopic analyses revealed that smaller (<5 nm) and well-dispersed hydrophilic domains contribute to better proton conducting properties. Hydrogen and oxygen permeability of 1 was 1-2 orders of magnitude lower than that of Nafion under both dry and wet conditions. Fuel cell was fabricated with 1 membrane and operated at 80 °C and 0.2 A/cm2 supplying H2 and air both at 60% or 90% RH. Ionomer 1 membrane showed comparable performance to Nafion and was durable for 5000 h without distinct degradation.

Original languageEnglish
Pages (from-to)1762-1769
Number of pages8
JournalJournal of the American Chemical Society
Issue number5
Publication statusPublished - 2006 Feb 8
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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