Sulfonated polyimides are new ionomer materials intened for use in special applications, namely proton exchange membranes for fuel cells. Owing to their good thermal stability, good mechanical properties, low gas permeability and good ionic conducitiy, polyimide polymers were good candidates for preparing proton exchange membranes. But, sulfonated polyimides are degraded in aqueous medium. The hydrolysis of sulfonated polyimide leads to polymer chain scissions. Such a decrease in the molecular weight also explain the brittleness