A systematic modeling analysis for the swollen weight (S-w) and the room temperature conductivity (sigma (25)) of the composite electrolytes of polyethylene glycol based waterborne polyurethane-polytetramethylene gylcol based polyurethane-polyethylene oxide (denoted as WPU (PEG)-WPU (PTMG)-PEO) was performed. Using a mixture design approach, empirical models are fitted and plotted as contour diagrams which facilitate revealing the synergistic/antagonistic effects among the mixed polymers. The contour plots show that the maximum S-w appears at point X-3 (PEO 95%, WPU(PEG) 5%), while the maximum sigma (25) (1.8 x 10(-3) S cm(-1)) appears in the ternary region (WPU(PEG) 19 similar to 38%, WPU(PTMG) 9 similar to 21%, and PEO 47 similar to 68%). The results are reasonably explained from the interactions among polymers on the basis of their molecular structures. The thermal analysis of the composite films is performed to demonstrate the speculations about the interactions among the mixed polymers. Arrhenius plots of conductivities reveal that the composite electrolytes within the maximum sigma (25) region possess the maximum conductivity from 5 degreesC to 65 degreesC with the activation energy of 5.67 kcal mol(-1).