Controlled molecular weight poly(arylene ether sulfone) oligomers with aromatic amine end groups and systematically varied degrees of disulfonation were synthesized by direct polymerization of disulfonated and non-sulfonated 4,40-dichlorodiphenylsulfone. The oligomers were crosslinked with a tetrafunctional epoxy curing agent in the membrane casting process. Water uptake and IEC were investigated to understand how the structure and ion content affected the fixed charge concentrations (moles of ions/L of sorbed water). The hydrated mechanical properties of these copolymer networks were also studied in light of their ion contents and water uptake. At similar IECs, membranes with shorter similar to 5000 Da oligomers absorbed less water than those with similar to 10,000 Da blocks. The salt permeabilities correlated with water uptake and fixed charge density. Among the crosslinked membranes, the one with the 10,000 Da oligomer and with 50% disulfonation (mB5-10) had an excellent combination of water uptake, hydrated mechanical properties, fixed charge density, and low salt permeability. (C) 2017 Published by Elsevier Ltd.