THERMAL-STABILITY AND MORPHOLOGY OF POLYMER ELECTROLYTES BASED ON EUROPIUM BROMIDE

The usual two-solvent technique was used to prepare a series of PEO (MW = 5 x 10(6)) electrolytes containing trivalent salts of Eu with compositions between n = 80 and n = 3 (n-O/M). The films have been characterized in detail by Differential Scanning Calorimetry (DSC), scanning electron microscopy energy dispersive X-ray microanalysis (SEM/EDX) and X-ray powder diffraction. The studies have shown that all the films with n greater than or equal to 12 exhibit an endothermic peak around 65 degrees C, which is associated with the melting of crystalline PEO. For salt-rich films, 3 less than or equal to n less than or equal to 8, this peak was depressed to an onset of approximately 50 degrees C. In addition, all the films showed a broader endotherm between the melting of PEG and the onset of decomposition around 250-260 degrees C, which is attributed to the melting of crystalline PEO/salts complexes. Films with n approximate to 16 showed a smaller endotherm around 60 degrees C, which was not observed upon reheating, thus suggesting that it results from the eutectic phase of PEG and PEO/salt complex. Furthermore, a stoichiometric complex with unusual properties was observed for n approximate to 3. It is a glassy, transparent and fragile material when no traces of water can be detected.