Poly(ethylene oxide) (PEO) oligomers having sulfonamide groups or ethylimidazolium groups on the chain ends were prepared, and they were mixed to form molten salt at the chain ends of these PEO derivatives. For the PEO (with average molecular weight of 150) having sulfonamide groups, its glass transition temperature (T-g) decreased drastically from 3.2 degrees C to -61.6 degrees C and ionic conductivity also increased to 6.12 X 10(-5) S.cm(-1) at 50 degrees C by mixing with PEO having ethylimidazolium groups. The effect of the molecular weight of these PEO chains on the ionic conductivity was much less than that for ordinary PEO hybrids. The excellent ionic conductivity was comprehended as the considerable decrease of T-g after the molten salt formation.