POLYETHER, POLY(N,N-DIMETHYLACRYLAMIDE), AND LICLO4 COMPOSITE POLYMERIC ELECTROLYTES

The results of detailed studies of the ionic conductivity, ultrastruct ure, and morpholgy of polyether-poly(N,N-dimethylacrylamide) electroly tes are presented and discussed. These composite electrolytes have bee n studied using differential scanning calorimetry (-110-150 degrees C) , with FT-IR spectroscopy (20-85 degrees C) and impedance analysis (-2 0-100 degrees C): Room temperature FT-Raman spectroscopy, SEM, and X-r ay energy dispersive studies have also been performed. Highly crystall ine poly(ethylene oxide) and amorphous or low-crystalline oxymethylene -linked poly(ethylene oxide) are used as polyether matrices for compos ite electrolytes. It is shown that interactions of lithium cations wit h polyether oxygens and the carbonyl oxygens of the ''filler'' poly(N, N-dimethylacrylamide) lead to the formation of various types of comple xes. These interactions can be classified as Lewis acid-base reactions . The formation of different types of complexes modifies the ultrastru cture and enhances the subambient and ambient temperature ionic conduc tivity of these electrolytes in comparison to the pure polyether-LiClO 4 electrolyte. The increase in the conductivity is attributed to the p resence of a highly flexible uncomplexed polyether phase surrounding f iller particles. The temperature dependence of ionic conductivity is A rrhenius at ambient and subambient temperatures and VTF at higher temp eratures. The order-disorder transition temperature calculated on the basis of a semiempirical model is found to be equal to the onset tempe rature of the melting peak of the crystalline poly(ethylene oxide) for these semicrystalline electrolytes or equal to 1.2 times the glass tr ansition temperature of the polyether-LiclO(4) electrolyte for the cor responding amorphous systems. Assuming that the enhanced conductivity of these composite polymer electrolytes is associated with interphase phenomena, the conductivity results were analyzed in terms of a model based on effective medium theory.