Nanophase separated ionic-hydrophobic block copolymers have shown promise as proton exchange membranes than random copolymers. A series of multiblock copolymers composed of alternating segments of fully disulfonated poly(arylene ether sulfone)s and highly fluorinated poly(arylene ether sulfone)s were evaluated for their potential as proton exchange membranes. Block length and chemical composition were the two major structural variables influencing the properties. Significantly, higher water and proton transport properties were observed for the higher block length materials. Water uptake was controlled by controlling the ratio between the hydrophobic and hydrophilic block lengths. These ion containing multiblock copolymers showed promise as some of the more selective PEMs in terms of achieving both high proton conductivity and low water uptake. Detailed structure-property relationships are provided in the paper. (c) 2008 Elsevier B.V. All rights reserved.