Ionomer thermodynamic interrelationships associated with wettability, surface energy, swelling, and water transport

Donghui Wang, Chris J. Cornelius

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Polytetrafluoroethylene (PTFE), perfluorosulfonic acid (PFSA), sulfonated poly(phenylene) (sPP), and (poly[t-butyl styrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butyl styrene) (tBS-HI-S-HI-tBS or PBC) films wetting properties and surface energy were evaluated by measuring their contact angles. Increasing ionomer sulfonate group concentration led to an equivalent decrease in contact angle due to increasing surface energy. Owens and Wendt, Wu, and Kwok and Neumann's models were used to estimate these material's total surface energy (γS); and their dispersive (γSd) and polar (γSp) force components. The Owens and Wendt model provided reasonable γS, γSd, and γSp estimates for sPP with an ion-exchange capacity (IEC) of 1.8 that had a predicted γS of 25.4 mJ/m2, and a PBC series with an IEC ranging from 0.0 to 2.0 having a γS change from 14.1 to 23.5 mJ/m2 due to increasing sulfonic acid group concentration. PFSA's γS was best fit using the Kwok and Neumann model (γS = 19.1 mJ/m2). Ionomer film swelling behavior in water was evaluated at steady-state, and as a function of time. These results revealed anisotropic swelling in all dimensions (x, y, and z) with the greatest change in the film's thickness and the smallest in its manufacturing processing direction. In general, film swelling was characterized as Fickian with the exception being Nafion 212 (NF212) that was non-Fickian. Steady-state changes in film mass due to water swelling were used to estimate effective diffusion coefficients Dw. However, highly processed Nafion 212 had non-Fickian diffusion properties. Material γS, swelling behavior, and water transport characteristics were dependent upon chemical composition and IEC.

Original languageEnglish (US)
Pages (from-to)126-138
Number of pages13
JournalEuropean Polymer Journal
Volume85
DOIs
StatePublished - Dec 1 2016

Keywords

  • Contact angle
  • Hydrophobicity and hydrophilicity
  • Ionomer
  • Surface energy
  • Water transport
  • Wettability and swelling

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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