Ternary polymer composites for gel electrolytes via a mixture design approach

A systematic modeling analysis for the swollen weight (S_w) and the room temperature conductivity (σ25) 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 X₃ (PEO 95%, WPU (PEG) 5%), while the maximum σ25 (1.8 x 10^-3 S cm^-1) appears in the ternary region (WPU(PEG) 19 ∼ 38%, WPU(PTMG) 9 ∼ 21%, and PEO 47 ∼ 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 σ25 region possess the maximum conductivity from 5°C to 65°C with the activation energy of 5.67 kcal mol^-1.