Blends comprising a sulfonated block copolymer and particulate carbon are useful materials for membranes, films and coatings in applications which require high dimensional stability, high water vapor transport, high conductivity, and low flammability. The sulfonated block copolymer comprises 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 is a polymer block containing from about 10 to about 100 mol percent sulfonic acid or sulfonate functional groups based on the number of monomer units of the B block.