Starting from a 5 wt% ion power Nafion (R) solution and dissolving the dry residue in a suitable solvent (10 wt% solution in dimethylacetammide), re-cast Nation films were developed for polymer electrolyte fuel cells (PEFCs) application. The used Doctor-Blade casting technique allowed to prepare scaled-up membranes comparable to the commercial Nation ones with good mechanical resistance, thickness homogeneity and an excellent reproducibility. The differences between the re-cast membrane nanostructure and that of the commercial Nation were investigated by synchrotron small-angle X-ray scattering. The obtained re-cast membrane shows at ambient conditions a semi-crystalline structure with a typical correlation length of about 86 angstrom and an intercluster Bragg distance of 37 angstrom, quite different from the values of commercial film. Observation on the swelling of the films revealed that the semi-crystalline structure, once soaked in water, swells less than the ionomeric part, leading to an unusual small-angle X-ray scattering (SAXS) profile in which the matrix and the ionomer peak are significantly overlapped. The ionic conductivity measured at T = 80 degrees C shows slightly higher values for the re-cast Nafion membrane. A power density of about 0.490 W cm(-2) at 0.6 V and at T = 80 degrees C in humidified hydrogen/air was obtained for the developed membrane. (c) 2005 Elsevier B.V. All rights reserved.