Two series of sulfonated poly(arylene ether nitrile ketone) ionomers containing potential crosslinkable nitrile groups were synthesized in high yield by direct aromatic nucleophilic polycondensation of 1,4-bis-(4-hydroxyphenyl)-2,3-dicyano -naphthalene (3) with different molar ratio of disodium 5,5'-carbonyl-bis-(2-fluorobenzene-sulfonate) (4) to 5,5'-carbonyl-bis-(2-fluorobenzene) (5) or 4,4-biphenol (7). Subsequently, the sulfonated polymeric ionomers were in situ crosslinked when cast into membranes from solution at 180 degrees C under nitrogen protection. The structure of the synthesized polymers was characterized by H-1-nuclear magnetic resonance (NMR), Fourier-transform infrared spectra, and elemental analysis. Comparing with the original polymeric membranes, the crosslinked membranes showed much better thermal and hydrolytic stabilities and superior mechanical properties as well as much lower swelling behavior, which were even better than Nafion 117 membrane. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 1981-1988, 2013