The results of detailed studies of the ionic conductivity, ultrastructure, and morpholgy of polyether-poly(N,N-dimethylacrylamide) electrolytes are presented and discussed. These composite electrolytes have been studied using differential scanning calorimetry (-110-150 degrees C), with FT-IR spectroscopy (20-85 degrees C) and impedance analysis (-20-100 degrees C) : Room temperature FT-Raman spectroscopy, SEM, and X-ray energy dispersive studies have also been performed. Highly crystalline poly(ethylene oxide) and amorphous or low-crystalline oxymethylene-linked poly(ethylene oxide) are used as polyether matrices for composite electrolytes. It is shown that interactions of lithium cations with polyether oxygens and the carbonyl oxygens of the "filler" poly(N,N-dimethylacrylamide) lead to the formation of various types of complexes. These interactions can be classified as Lewis acid-base reactions. The formation of different types of complexes modifies the ultrastructure and enhances the subambient and ambient temperature ionic conductivity of these electrolytes in comparison to the pure polyether-LiClO4 electrolyte. The increase in the conductivity is attributed to the presence of a highly flexible uncomplexed polyether phase surrounding filler particles. The temperature dependence of ionic conductivity is Arrhenius at ambient and subambient temperatures and VTF at higher temperatures. The order-disorder transition temperature calculated on the basis of a semiempirical model is found to be equal to the onset temperature of the melting peak of the crystalline poly(ethylene oxide) for these semicrystalline electrolytes or equal to 1.2 times the glass transition temperature of the polyether-LiclO(4) electrolyte for the corresponding 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.