An amide 6-b-ethylene oxide copolymer (Pebax(R)) was investigated as an ionic conducting matrix. Transparent and flexible films containing LiClO4 were prepared with ionic conductivities in the range of 10(-6) S cm(-1) at room temperature. The conductivity values gradually increased when the films were heated (10(-4) S cm(-1) at 100 degrees C). The conductivity dependence on temperature could be described according to the classical Arrhenius plots over the temperature range of 22 to 100 degrees C. The glass transition temperature was determined by differential scanning calorimetry. The T-g of the Pebax/LiClO4 system increases for samples containing high salt concentration, as expected. The polymer electrolyte morphology was analyzed by transmission electron microscopy. Salt aggregation was observed in all samples. This was confirmed by electron spectroscopic images selective for chlorine. The electrochemical stability window of the Pebax/LiClO4 electrolytes as investigated by cyclic voltammetry was in the range of 4.0 V.