Synthesis of polyethylene-based proton exchange membranes containing PE backbone and sulfonated poly(arylene ether sulfone) side chains for fuel cell applications

Hyung Kyu Kim, Min Zhang, Xuepei Yuan, Serguei N. Lvov, T. C.Mike Chung

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

This paper discusses a new class of proton exchange membranes (PEMs) that are based on a well-controlled polyolefin graft copolymer containing a polyethylene (PE) backbone and several sulfonated poly(arylene ether sulfone) (s-PAES) side chains. The chemistry involves a graft-onto reaction between high molecular weight PE with few pendent benzyl bromide groups and poly(arylene ether sulfone) (PAES) with two terminal phenol groups. The resulting PE-g-PAES graft copolymer, with predetermined backbone molecular weight, graft density, and graft length, was solution-cast into uniform film (thickness 20-40 μm), followed by a heterogeneous sulfonation reaction of PAES side chains to obtain the desired PE-g-s-PAES PEMs with a high sulfonation level. The unique combination of hydrophobicity, semicrystallinity, and high molecular weight of the PE backbone offers PEM with a stable (nonswellable) matrix. The embedded hydrophilic s-PAES proton-conductive domains show only moderate water uptake, even with a high ion exchange capacity (IEC >3 mmol/g in the s-PAES domains). Compared to Nafion 117, most PE-g-s-PAES PEMs show similar hydration numbers (λ <15) but higher proton conductivity (up to 160 mS/cm). More interestingly, all PE-g-s-PAES PEMs show higher through-plane conductivity than in-plane conductivity. Evidently, a thin hydrophobic PE layer is formed on the PEM surfaces due to the low surface energy of PE, resulting in anisotropic conductivity. Overall, this newly developed PE-g-s-PAES membrane offers a combination of desirable properties, including conductivity, water uptake, mechanical strength, and cost-effectiveness for fuel cell applications.

Original languageEnglish (US)
Pages (from-to)2460-2470
Number of pages11
JournalMacromolecules
Volume45
Issue number5
DOIs
StatePublished - Mar 13 2012

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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