The synthesis and characterization of new di- and tetra-sulfonated ether diketone monomers are described. From these monomers, a wide series of sulfonated poly(arylene ether ketone)s (SPAEK) are synthesized by varying the sulfonic acid repartition along the polymer backbones. Their chemical structures are thoroughly characterized by NMR. From these polymers tough membranes are obtained from solution casting method and their water uptake, ionic conductivity, and water/gas permeation properties are determined and compared with those of Nafion membrane. Preliminary fuel cell tests show that SPAEK membranes are promising candidates for fuel cell application. This work brings new insights concerning the beneficial effects of introducing densely sulfonated monomers in a polyarylether macromolecular structure along with fluorinated groups improving conductivity while reducing unwanted excessive swelling. (c) 2017 Wiley Periodicals, Inc.