Acid-base blend proton exchange membrane films were prepared from sulfonated poly(phthalazinone ether ketone)s (SPPEK)s, either polymerized from sulfonated monomer (M-SPPEK) or post-sulfonated (P-SPPEK), and three kinds of aminated polysulfones, namely: Udel(R) PSf animated ortho to ether linkage (ortho-O-APSf), PSf phenylmethylene aminated ortho to the sulfone linkage (ortho-S-PMAPSf), or 6F polysulfone aminated ortho to the sulfone linkage (ortho-S-6F-APSf). Films were prepared by casting mixed N,N-dimethylacetamide (DMAc) solutions of (SPPEK)s in ammonium or sodium salt form and aminated polysulfones, followed by treatment of the blend membrane films in aqueous sulfuric acid. The blend membrane films showed slightly lower thermal stabilities than SPPEKs. M-SPPEK-based blend membrane films showed an obvious decrease in proton conductivity compared with their parent sulfonated polymer, whereas the P-SPPEK-based blend membrane films showed similar proton conductivities to their parent sulfonated polymer from room temperature to about 80 C. All blend membrane films showed increased swelling stability. (C) 2004 Elsevier B.V. All rights reserved.