Sulfonated polyimides, membranes and fuel cells

The title sulfonated polyimides comprise repeating units I and II (Z1-2 = tetravalent group; Ar1-2 = arom. divalent group). The polymers are useful as ion-exchange membranes, esp. for fuel cells. The membranes have good durability and the fuel cells can be used in elec. vehicles. A polymer was prepd. by polymn.. of 4,4'-diamino-(1,1'-biphenyl)-2,2'-disulfonic acid, 4,4'-methylenebisbenzeneamine, and 5,5'-oxybis(1,3-isobenzofurandione)