Premium
Proton exchange membranes by radiation grafting of styrene onto FEP films. IV. Evaluation of the states of water
Author(s) -
Gupta Bhuvanesh,
Haas Otto,
Scherer Günther G.
Publication year - 1995
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1995.070570709
Subject(s) - grafting , membrane , bound water , differential scanning calorimetry , polymer chemistry , tetrafluoroethylene , styrene , hexafluoropropylene , chemistry , ionomer , proton , chemical engineering , materials science , copolymer , molecule , polymer , organic chemistry , thermodynamics , biochemistry , physics , engineering , quantum mechanics
The nature of water in proton exchange membranes, obtained by radiation grafting of styrene onto poly(tetrafluoroethylene‐ co ‐hexafluoropropylene) (FEP) films and subsequent sulfonation, was investigated by differential scanning calorimetry. It was found that the membranes contained three different types of water, which were categorized as freezing‐free, freezing‐bound, and nonfreezing water. The degree of grafting had a considerable influence on the relative ratios of these three types of water molecules. The nonfreezing water per ion‐exchange site ratio was found to be independent of the degree of grafting. However, freezing‐free and freezing‐bound water per ionic site ratios increased with increasing graft levels. A correlation between the water uptake and the structural changes occurring in the membrane as a function of the degree of grafting was established. © 1995 John Wiley & Sons, Inc.