Poly(sodium(2-sulfamate-3-carboxylate)isoprene)-b-poly(ethylene oxide) and poly(ethylene oxide)-b-poly(sodium(2-sulfamate-l-carboxylate)isoprene)-b-poly(ethylene oxide) double hydrophilic block copolymers were prepared by selective post polymerization reaction of the polyisoprene block, of poly(isoprene-b-ethylene oxide) diblocks or poly(ethylene oxide-b-isoprene-b-ethylene oxide) triblock precursors, with N-chlorosulfonyl isocyanate. The precursors were synthesized by anionic polymerization high vacuum techniques and had narrow molecular weight distributions and predictable molecular weights and compositions. The resulting double hydrophilic block copolymers were characterized by FTIR and potentiometric titrations in terms of the incorporated functional groups. Their properties in aqueous solutions were studied by viscometry and dynamic light scattering. The latter techniques revealed a complex dilute solution behavior of the novel block copolymers, resulting from the polyelectrolyte character of the functionalized PI block and showing a dependence on solution ionic strength and pH. (c) 2005 Wiley Periodicals, Inc.