Single-step synthesis of sulfonated polyoxadiazoles and their use as proton conducting membranes

Dominique Gomes*, Jerusa Roeder, Mariela L. Ponce, Suzana Nunes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

A single-step approach for the synthesis of sulfonated polyoxadiazoles from hydrazine sulfate was developed using non-sulfonated diacids in polyphosphoric acid. The post-sulfonation conditions were optimized by varying reaction time, medium and reagent concentrations in sulfuric acid, oleum and/or their mixtures. For the first time, a series of sulfonated polyoxadiazoles with ion exchange capacity (IEC) ranging from 1.26 to 2.7 meqiv. g-1 and high molecular weight (about 40,0000 g mol-1) were synthesized. The structures of the polymers were characterized by elemental analysis, 1H NMR, and FTIR. Sulfonated polyoxadiazole membranes with high thermal stability indicated by observed glass-transition temperatures (Tg) ranging from 364 to 442 °C in sodium salt form and from 304 to 333 °C in acid form and with high mechanical properties (storage modulus about 3 GPa at 300 °C) have been prepared. The membrane stability to oxidation was investigated by soaking the film in Fenton's reagent at 80 °C for 1 h. The sulfonated polyoxadiazole membranes exhibited high oxidative stability, retaining 98-100% of their weight after the test. Proton conductivity values with the order of magnitude of 10-1 to 10-2 S cm-1 at 80 °C and with relative humidity ranging from 100% to 20% were obtained.

Original languageEnglish (US)
Pages (from-to)49-59
Number of pages11
JournalJournal of Power Sources
Volume175
Issue number1
DOIs
StatePublished - Jan 3 2008

Keywords

  • Fuel cell
  • PEMFC
  • Polyoxadiazole
  • Proton conductivity
  • Sulfonation

ASJC Scopus subject areas

  • Electrochemistry
  • Fuel Technology
  • Materials Chemistry
  • Energy (miscellaneous)

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