Polymer electrolytes with room temperature conductivities of >10(-4) S/cm were prepared by encapsulating solutions of LiN(SO2CF3)(2) (or LiSO3CF3 or LiPF6) in oligomeric poly(ethylene glycol) dimethyl ethers in a poly(vinylidene fluoride)-hexafluoropropene copolymer. The 100 to 200 mu m thick membranes prepared have good mechanical strength and are "dry" with practically no volatility at least up to 70 degrees C. Because of these properties and the structural similarities between poly(ethylene glycol) dimethyl ethers (PEGDME) and polyethylene oxide (PEO) we call them PEO-like.