Synthesis and characterization of sulfonated copolyimides via thermal imidization for polymer electrolyte membrane application

Eun Young Jung, Boknam Chae, Se Jin Kwon, Hyun Chul Kim, Seung Woo Lee

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10 Scopus citations

Abstract

A series of soluble copoly(amic acid) precursors were synthesized with varying compositions by the conventional polycondensation of 3,3′,4,4′-biphenyltetracarboxylic anhydride (BPDA) and 3,3′-sulfonyldianiline (SDA) using 4,4′-diaminodiphenyl ether-2,2′-disulfonic acid (ODADS), a sulfonated diamine, as a third component in NMP. The synthesized precursor polymers are soluble in polar aprotic solvents. The chemical structures and inherent viscosities of the copoly(amic acid)s were determined by 1H NMR spectroscopy and viscometry, respectively. The free standing sulfonated copolyimide membranes were fabricated from solutions of the copoly(amic acid)s by a thermal imidization process and subsequent soaking in sulfuric acid solution. The chemical structure and thermal properties of the sulfonated copolyimides in the films were investigated in detail using FT-IR, DSC, and TGA. The sulfonated copolyimides show mainly three-step thermal degradation, with the degradation behavior being independent of the composition. In addition, the properties of the membranes were investigated, including their water uptake (WU), ion exchange capacity (IEC) and proton conductivity. The WU and IEC values of the sulfonated copolyimides were 8.12-38.0% and 0.18-2.05 meq/g, respectively, depending on the composition of the sulfonated diamine, and the proton conductivity of the copolyimides was dependent on the content of the sulfonated diamine. The proton conductivity values of the membranes were lower than that of Nafion 117, although their IEC values were higher.

Original languageEnglish
Pages (from-to)95-99
Number of pages5
JournalSolid State Ionics
Volume216
DOIs
StatePublished - 28 May 2012

Bibliographical note

Funding Information:
This study was supported by MEST and DGIST ( 10-BD-0101 , Convergence Technology with New Renewable Energy and Intelligent Robot) for the partial financial support and by the Human Resources Development Program of Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (No. 20104010100580 ) funded by the Korean Ministry of Knowledge Economy .

Keywords

  • FTIR spectroscopy
  • Proton exchange membrane
  • Sulfonated copolyimide
  • Sulfonated polyimide
  • Thermal imidization

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