The results of detailed studies of the ionic conductivity and ultrastructure of polymer blends complexed with LiClO4 are presented and discussed and include comparisons with undoped blends. These composite polymer electrolyte systems are studied over a temperature range -110 to 150 degrees C using differential scanning calorimetry (DSC), with room temperature FT-IR, and with -20 to 100 degrees C impedance analysis and consist of blends of poly(ethylene oxide) (PEG) or oxymethylene-linked PEO (OMPEO) with polyacrylamide (PAAM). The high molecular weight PAAM is found to inhibit the crystallization of PEO without impeding segmental motion. In fact the ionic conductivity is enhanced in the blends compared to the PEO-LiClO4, complex. Conductivities exceeding 10(-4) S/cm at room temperature were obtained for electrolytes prepared by the in situ polymerization of acrylamide in the polyether. Annealing the blends at 150 degrees C for 10-15 min makes the ultrastructure (recrystallization, melting, glass transitions) as initially observed by DSC less complex. Generally from DSC and FT-IR the ultrastructure appears to consist of emulsified PAAM complexed to itself and to polyether segments via Li+ cations surrounded by relatively uncomplexed polyether segments. At higher PAAM concentrations the PAAM-LiClO4 nonconducting cores increases in size, reducing the region of uncomplexed polyether; the ionic conductivity decreases. 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.