Substituents effect on the properties of sulfonated polyimide copolymers

Kenji Miyatake*, Tomohiro Yasuda, Masahiro Watanabe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


A series of sulfonated polyimide (SPI) copolymers containing methyl, methoxy, or fluorine groups were synthesized to elucidate the substituents effect on their proton conducting properties as well as thermal, hydrolytic, and oxidative stability for polymer electrolyte membrane fuel cell applications. SPIs of high molecular weight (Mw > 200 kDa, Mn > 80 kDa) along with the ion exchange capacity (IEC) varying between 1.34 and 1.91 mequiv/g were obtained, which gave tough, ductile, and flexible membranes by solution casting. The thermal properties of the SPIs were dominated by the electronic structure of the sulfonated aromatic rings. The electron-donating methyl groups lowered the thermal decomposition temperature. The hydrolytic and oxidative stability was roughly in the order of IEC (the higher IEC membranes were less stable). Fluorine groups, either as -F or -CF3, had negative effect on the hydrolytic and oxidative stability. In the water uptake and proton conductivity, hydrophobic components are rather more influential than the substituents. It was found out that the SPI(5, 8, 0.7) containing bis(phenoxy)biphenylene sulfone moieties as a rigid hydrophobic component showed the best balanced properties in terms of the stability and the proton conductivity for its rather low IEC.

Original languageEnglish
Pages (from-to)4469-4478
Number of pages10
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Issue number13
Publication statusPublished - 2008 Jul 1
Externally publishedYes


  • Conducting polymers
  • Fuel cells
  • Ionomers
  • Polyimides
  • Proton conduction

ASJC Scopus subject areas

  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry


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