Described herein are modified sulfonated block copolymers which comprise at least two polymer end blocks A and at least one polymer interior block B, wherein each A block contains essentially no sulfonic acid or sulfonate functional groups and each B block comprises sulfonation susceptible monomer units and, based on the number of the sulfonation susceptible monomer units, from about 10 to about 100 mol % of a functional group of formula (I) —SO2—NR1R2  (I) or of a salt thereof, methods of making them as well as methods of using them, e.g., as membrane materials for electrically or osmotically driven applications.