Anionic graft copolymers were prepared through ring-opening anhydride reactions between poly(ethylene oxide) monomethyl ethers (MPEG) and copolymers of maleic anhydride and styrene (SMA), methyl vinyl ether (MEMA) and ethylene (EMA), respectively. The carboxylic acid groups in the graft copolymers were neutralized with KOH, and films were prepared by solution casting. The materials were characterized by FTIR, NMR and DSC. Ionic conductivity and electrical relaxation have been studied as well. The EMA-MPEG 2000 graft copolymer showed the highest conductivity, sigma = 3 x 10(-5) S cm(-1) at 80 degrees C.