Steady-state and time-resolved fluorescence spectroscopic probing of microstructures and properties of perfluorinated polyelectrolyte membranes

A systematic luminescence spectroscopic study of the microstructures and pr operties of Nafion(R), the Dow Chemical films, and the newly synthesized su lfonimide ionomer membrane is reported. The strongly environment-sensitive luminescent probes 6-propionyl-2-(N,N-dimethylamino)naphthalene, 4-(N,N-dim ethylamino)benzonitrile, pyrene, and ethidium bromide were used. The result s suggest that the different perfluorinated ionomer membranes have generall y similar properties with respect to the luminescent molecular probes and t hat the membrane structures consist of a substantial region that may be cha racterized as a heterogeneous mixture of water molecules and branches of th e perfluorinated polymers. In addition, the effects of thermally stressing the ionomer membranes in an aqueous solution at temperatures up to 250 degr ees C on the properties of the membranes are evaluated and discussed. (C) 1 998 Elsevier Science S.A. All rights reserved.