Two kinds of alkali metal salts of poly(sulfoalkyl methacrylate)s (PSAMM) were prepared, with which the blend complexes of poly[oligo(oxyethylene) methacrylate] (PMEO(n)) were formed. These blend complexes contain neither organic plasticizer nor low molecular weight Li-salt and are considered to be single-cationic conductors which are characterized by stable dc ionic conductivity. Cationic conductivity is deeply influenced by the glass transition temperature, cation species, polar group (acrylonitrile), the concentration of polymeric salts, and the size of side-group in PSAMM. An optimum Li+-ionic conductivity of 1.1 x 10(-6) S cm-1 at 25-degrees-C is obtained for the blend complex P(0.6MEO18-0.4AN)/P(0.5SHMLi-0.5AN) (AN, acrylonitrile; SHMLi, lithium sulfohexyl methacrylate) with O/Li = 72.