A new kind of sulfonated copolyimides (SPIs) with higher hydrolysis stability containing both of naphthalene and phthalazinone moieties in polymer's main chain were successfully synthesized from 4

4′-bis(4-aminophenoxy)biphenyl-3

3′-disulfonic acid (BAPBDS)

1

2-dihydro-2-(4-aminophenyl)-4-［4-(4-aminophenoxy)phenyl］-phthalazin-1-one (DHPZDA) and 1

4

5

8-naphthalenetetracarboxylic dianhydride (NTDA) via direct polymerization

which are potentially utilized as proton exchange membrane in PEMFC.The obtained sulfonated polymers (SPIs) had high molecular weight with the inherent viscosity ranged from 0.41 to 1.00 dL/g in concentrated (95%) sulfuric acid when samples varied from 20% to 140% of sulfonation degree.The chemical structure of the SPIs was carefully characterized by FT-IR and 1H-NMR

and the thermo-behavior of copolymers by thermalgravimeteic analysis (TGA) was also investigated.The yellow

transparent and tough membranes cast from m-cresel solutions of the SPIs were obtained

which were utilized to investigate the physicochemical properties of these new copolymers. The data demonstrated that the membranes had better solubility and hydrolysis stabilities than the other analogeous SPIs.