Sulfonated block copolymers

Claim 1

A selectively sulfonated, selectively hydrogenated block polymer which is produced by the process of: reacting acetyl sulfate and a block copolymer in a solvent, each block copolymer molecule having at least two alkenyl polymer blocks A and at least one substantially completely hydrogenated conjugated diene block B, whereby sulfonic acid functional groups are primarily grafted to the block copolymer on the A blocks, and recovering the grafted block copolymer from the solvent, wherein: the block copolymer has two A blocks, each A block prior to hydrogenation is predominantly polymerized styrene units, the block copolymer has one B block positioned between the two A blocks, the B block prior to hydrogenation is predominantly polymerized butadiene units, the block copolymer has a number average molecular weight of 50,000 with said A blocks constituting 30 percent by weight of said copolymer prior to sulfonation, the residual ethylenic unsaturation of said B block after hydrogenation is less than about 2 percent of the ethylenic unsaturation of said B block prior to hydrogenation, the residual aromatic unsaturation of said A blocks after hydrogenation is greater than 95 percent of the aromatic unsaturation of said A blocks prior to hydrogenation, and the block copolymer contains 1 sulfonic acid group per 9 styrene units and the sulfonic acid groups are neutralized to sulfonate salts with sodium ions.