The composite electrolytes (CEs) were prepared by impregnating the ternary composites comprising polypropylene glycol-based waterborne polyurethane (denoted as WPU(PPG)), polytetramethylene glycol-based waterborne polyurethane (denote as WPW(PTMG), and polyethylene oxide (PEO) with LiClO4/PC. The data of the swollen weight (S-w) and the room-temperature conductivity tots) for CEs were fitted as empirical regression equations by using mixture design. These empirical equations were used to construct contour plots, facilitating comparisons of synergistic/antagonistic effects among the mixed polymers. The contour plots show that the maximum S-w (64.3%) appears at point X-3 (PEO 95% and WPU(PPG) 5%), while the maximum sigma(25) (approximate to 10(-3) S/cm) appears in a wide region (WPU(PPG) = 5-43%, WPU(PTMG) ( 37%, and PEO > 27%). Differential scanning calorimetry (DSC) results showed immiscibility between WPU(PTMG) and PEO and partial immiscibility between WPU(PPG) and WPU(PTMG)/ PEG. A polarized micrograph (PM) of the composites was also examined for PEO spherulites. The contour plot results of S-w and sigma(25) can be explained by the interactions among polymers on the basis of their molecular structures, also evidenced by both DSC and PM results.