The morphology of perfluorosulfonic ionomer molecules in N,N-dimethylformamide was investigated at different concentrations. Rheological, dynamic light scattering (DLS), and scanning electron microscopy (SEM) measurements were performed on the prepared perfluorosulfonic ionomer solutions or films. The ionomer molecules shrank from rodlike granules to spherelike ones at relatively low concentrations, and the spherelike granules aggregated together to form aggregates at higher concentrations, with capillary liquid bridge force as the driving force. As the solvent evaporated slowly at room temperature, the SEM image showed that the film was loosely stacked by granules and that aggregates formed in the solution. (c) 2007 Wiley Periodicals, Inc.