Anionic charges are introduced in the chain end of a series of poly(ethylene oxide)s (PEG) with molecular weights from 350 to 4000. The ionic conductivities of PEO oligomers with a carboxylate chain end (PEOAc(2)M(2)) and of those with benzenesulfonate (PEOBsM and PEOBs(2)M(2)) were analyzed. The mechanical properties of these salts were greatly influenced not only by PEO molecular weight but also by the chain end structure, PEOAc(2)M(2), which has charges on both chain ends, showed an amorphous phase, when the molecular weight of the PEO part was 400 and 600. These salts showed inherently high ionic conductivity, about 10(-4) S/cm at 323 K, because of the high mobility of carrier ions and the high ion concentration. The ionic conductivity increased with increasing the cation radius for all of the PEOAc(2)M(2). Since PEO showed low diffusion coefficient values, these salts were expected to be the single-ion conductors. Furthermore, a series of PEOBs salts was prepared and their ionic conductivity was analyzed. A series of PEOBsM became viscous liquids at a moderate molecular weight range, such as from 350 to 750. These salts showed higher ionic conductivities than PEOAc(2)M(2), reflecting lower dissociation energy of salt structure on the chain ends.