Introduction of a few oxy-propylene oxide units in the poly (ethylene oxide) chains prevents their recrystallization while keeping the good solvating properties of poly (ethylene oxide) towards lithium ions. These materials have been synthesized by an original anionic copolymerization process on solid catalysts at the LCPP. NMR characterization will be presented. Solid polymer electrolytes have been prepared with lithium salts. Some of them have been obtained from these materials by changing the terminal OH groups into NH, groups and curing with diepoxides. Crosslinking improves the mechanical properties but does not degrade the electrochemical properties which compare favorably with those of similar solid polymer electrolytes prepared with pure poly (ethylene oxide) (PEO).