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Water vapor sorption thermodynamics of the Nafion ionomer membrane

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Author

Summary, in English

The water interactions of polymer electrolyte membranes are of significant interest when these materials are used in for example fuel cells. We have therefore studied the sorption thermodynamics of Nafion 117 with a sorption calorimeter that simultaneously measures the sorption isotherm and the mixing (sorption) enthalpy. This unique method is suitable for investigating the sorption thermodynamics of ionic polymers. The measurements were made at 25 °C on a series of samples dried at different temperatures from 25 to 120 °C. The sorption isotherms indicate that the samples dried at 120 °C lost about 0.8 more water molecules per sulfonic group during the drying than did the samples dried at 25 °C, and this result was verified gravimetrically. The mixing enthalpies showed several peaks or plateaus for the samples dried at 60-120 °C. This behavior was seen up to about 2 water molecules per sulfonic group. As these peaks were not directly related to any feature in the sorption isotherm they probably have their origin in a secondary process, such as a reorganization of the polymer.

Publishing year

2013

Language

English

Pages

8561-8570

Publication/Series

The Journal of Physical Chemistry Part B

Volume

117

Issue

28

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Chemical Sciences

Keywords

  • Ionomer
  • Nafion
  • water vapor
  • sorption
  • sorption isotherm
  • sorption enthalpy

Status

Published

ISBN/ISSN/Other

  • ISSN: 1520-5207