Origin of Toughness in Dispersion-Cast Nafion Membranes

Journal Article · Mon Mar 23 00:00:00 EDT 2015 · Macromolecules

DOI:https://doi.org/10.1021/ma502538k· OSTI ID:1176818

Kim, Yu Seung ^[1]; Welch, Cynthia F. ^[1]; Hjelm, Rex P. ^[1]; Mack, Nathan H. ^[1]; Labouriau, Andrea ^[1]; Orler, E. Bruce ^[1]

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1. Sensors and Electrochemical Devices Group, ‡Polymers and Coatings Group, §Materials Science in Radiation & Dynamic Extremes Group, ∥Physical Chemistry & Applied Spectroscopy Group, and ⊥Chemical Diagnostics and Engineering Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States

In this study, the gelation behavior of Nafion dispersions was investigated using small-angle neutron scattering to better understand the mechanical toughness of dispersion-cast Nafion membranes. Three types of gelation were observed, depending on dispersing fluids: (i) homogeneous, thermally reversible gelation that was present in most aprotic polar dispersing fluids; (ii) inhomogeneous, thermally irreversible gelation as films, found in alcohols; and (iii) inhomogeneous, thermally irreversible gelation which precipitates in water/monohydric alcohol mixtures. The mechanical toughness of dispersion-cast Nafion membranes depends on the dispersing fluid, varying by more than 4 orders of magnitude. Excellent correlation between the critical gelation concentration and mechanical toughness was demonstrated with the Nafion membranes cast at 140 °C. Additional thermal effects among Nafion membranes cast at 190 °C were qualitatively related to the boiling point of dispersing fluids. Little correlation between mechanical toughness and percent crystalline area of Nafion was observed, suggesting that the origin of mechanical toughness of dispersion-cast Nafion membranes is due to chain entanglements rather than crystallinity. Finally, the correlation between critical gelation concentration and mechanical toughness is a new way of predicting mechanical behavior in dispersion-cast polymer systems in which both polymer-dispersing fluid and polymer–polymer interactions play a significant role in the formation of polymer chain entanglements.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Hydrogen Fuel Cell Technologies Office (HFTO)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1176818
• Alternate ID(s): OSTI ID: 1337083
• Report Number(s): LA-UR-14-29620
• Journal Information: Macromolecules, Journal Name: Macromolecules Vol. 48 Journal Issue: 7; ISSN 0024-9297
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY