Proton conducting crosslinked membranes by polymer blending of triblock copolymer and poly(vinyl alcohol)

Do Kyoung Lee, Jung Tae Park, Jin Kyu Choi, Dong Kyu Roh, Jung Hyun Lee, Yong-Gun Shul, Jong Hak Kim

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Abstract

Proton conducting crosslinked membranes were prepared using polymer blends of polystyrene-b-poly(hydroxyethyl acrylate)-b-poly(styrene sulfonic acid) (PS-b-PHEA-b-PSSA) and poly(vinyl alcohol) (PVA). PS-b-PHEA-b-PSSA triblock copolymer at 28:21:51 wt% was synthesized sequentially using atom transfer radical polymerization (ATRP). FT-IR spectroscopy showed that after thermal (120 °C, 2 h) and chemical (sulfosuccinic acid, SA) treatments of the membranes, the middle PHEA block of the triblock copolymer was crosslinked with PVA through an esterification reaction between the -OH group of the membrane and the -COOH group of SA. The ion exchange capacity (IEC) decreased from 1.56 to 0.61 meq/g with increasing amount of PVA. Therefore, the proton conductivity at room temperature decreased from 0.044 to 0.018 S/cm. However, the introduction of PVA resulted in a decrease in water uptake from 87.0 to 44.3%, providing good mechanical properties applicable to the membrane electrode assembly (MEA) of fuel cells. Transmission electron microscopy (TEM) showed that the membrane was microphase-separated with a nanometer range with good connectivity of the SO3H ionic aggregates. The power density of a single H 2/O2 fuel cell system using the membrane with 50 wt% PVA was 230 mW/cm2 at 70 °C with a relative humidity of 100%. Therrnogravimetric analysis (TGA) also showed a decrease in the thermal stability of the membranes with increasing PVA concentration.

Original languageEnglish
Pages (from-to)549-554
Number of pages6
JournalMacromolecular Research
Volume16
Issue number6
DOIs
Publication statusPublished - 2008 Jan 1

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All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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