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Relationship Between Methanol Permeability and Structure of Different Radiation‐Grafted Membranes
Author(s) -
Kallio T.,
Kisko K.,
Kontturi K.,
Serimaa R.,
Sundholm F.,
Sundholm G.
Publication year - 2004
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.200400060
Subject(s) - membrane , methanol , small angle x ray scattering , direct methanol fuel cell , lamellar structure , aqueous solution , nafion , materials science , chemical engineering , methanol fuel , fluoride , polymer chemistry , chemistry , inorganic chemistry , organic chemistry , composite material , electrochemistry , scattering , biochemistry , physics , electrode , anode , optics , engineering
Abstract Styrene grafted and sulfonated poly(vinylidene fluoride) and poly(vinylidene fluoride‐ co ‐hexafluoropropylene) films are candidates as electrolytes in direct methanol fuel cells. Their behaviour in water, 1 and 3 mol dm –3 aqueous methanol, and pure methanol were studied. According to SAXS results, water and methanol‐water solutions have similar effects on the membranes, i.e., the lamellar period increases and the ionic domains enlarge. Furthermore, differences in the ionic domain structures in pure methanol and water were observed. These structural changes together with dissimilar liquid uptakes in water and in methanol are reflected as changes in the conductivities. An increase in the SAXS intensity and changes in the Bragg distance of the ionic peak were observed in methanol compared to aqueous solutions. This may be related to the hydrophobicity of the CH 3 group on methanol. Dissimilarities in methanol permeability through the radiation‐grafted membrane can be related to structural differences in membranes observed with SAXS. Permeabilities were observed to be lower for the radiation‐grafted membranes compared to Nafion® 115, which compensates for the higher area resistance of the experimental membranes and thus improves their performance in a fuel cell.