The ideal electrolyte material for a solid-state battery would have the ionic conductivity of a liquid, the mechanical properties of a solid, and the formability of a commodity thermoplastic. The ionic conductivity changed with the molecular weight of the polymer, it varies inversely with the glass transition temperature. In our study, to achieve high ionic conductivity, we synthesize copolymer PDMS/PEO as polymer electrolytes by a simple method, one step of catalytic ring opening polymerization using Maghnite-H+ (Mag-H+), a montmorillonite sheet silicate clay exchanged with protons. It is preferred for its many advantages: a very low purchase price compared to other catalysts, the easy removal of the reaction mixture. The reaction of copolymerization is carried out in chloroform at 60°C for 10 h. POE used is POE 400 and POE 1000. PDMS with a Tg of -123°C was synthesized. Various techniques, including 1H-NMR, IR, DSC, XRD and TGA were used to elucidate structural characteristics and thermal properties of catalyst and products. Analyses results confirm the synthesis of the copolymer (PDMS / PEO) with different percentage composition of each polymer. Cationic mechanism for the reaction was proposed.