Synthesis of 2,2 '-hindered pyridine containing semifluorinated polytriazoles and investigation for low-temperature proton exchange membrane application with enhanced oxidative stability

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Sambit Roy - , Indian Institute of Technology Kharagpur (Author)
  • Arijit Ghorai - , Indian Institute of Technology Kharagpur (Author)
  • Hartmut Komber - , Leibniz Institute of Polymer Research Dresden (Author)
  • Brigitte Voit - , Leibniz Institute of Polymer Research Dresden (Author)
  • Susanta Banerjee - , Indian Institute of Technology Kharagpur (Author)

Abstract

A series of new sulfonated copolytriazoles were prepared from a novel fluorinated diazide monomer with pyridine moiety to enhance both the oxidative stability and proton conductivity of proton exchange membranes. These proton donor-acceptor based copolymers and homopolymers were synthesized by click cycloaddition polymerization of the dialkyne monomer 1,2,4,5-tetrafluoro-3,6-bis(prop-2-yn-1- yloxy)benzene (TFAK) with or without the pyridine containing diazide monomer 2,2'-bis(4-(4-azidophenoxy)-3-(trifluoromethyl)phenyl)pyridine (PYFAZ) and the sulfonated diazide monomer 4,4'-diazido-2,2'-stilbenedisulfonic acid disodium salt (DSSAZ). H-1, C-13, and F-19 NMR, in addition to FTIR analyses, confirm the formation of polytriazoles with a graded degree of sulfonation between 70% and 100%. The solution cast membranes were flexible and showed high chemical, thermal and mechanical properties. Inclusion of pyridine moiety proved to play a significant role in increasing peroxide stability by quenching hydroxyl and hydroperoxide radicals and forming pyridine-N-oxide, which was analyzed by EPR and FTIR spectroscopy. The presence of pyridine moiety also enhanced proton conductivity owing to the presence of the weakly basic nitrogen in pyridine that acts as a proton hopping site. AFM and HR-TEM images of the membranes indicated the formation of phase-separated morphology and that became more pronounced with the increase in the degree of sulfonation. The membranes obtained from PYFTSH-90 copolymer exhibited proton conductivity of 125 mS cm(-1) at 80 degrees C, which is comparable to Nafion-117. The proton conductivity of PYFTSH-90 was further increased to 139 mS cm(-1 )at 90 degrees C. Thus, three significant objectives have been fulfilled in this work, namely (i) high proton conductivity, (ii) high hydrolytic stability, and (iii) high peroxide stability. These properties demonstrate that these copolymer membranes are potentially highly suitable for application in low-temperature proton exchange membrane fuel cell (PEMFC).

Details

Original languageEnglish
Number of pages12
JournalEuropean Polymer Journal
Volume136
Publication statusPublished - 5 Aug 2020
Peer-reviewedYes
Externally publishedYes

External IDs

Scopus 85088747651
ORCID /0000-0002-4531-691X/work/148608001

Keywords

Keywords

  • Click polymerization, Oxidative stability, Polyelectrolyte membrane, Proton conductivity