Blending thermoplastic polyurethanes and poly(ethylene oxide) for composite electrolytes via a mixture design approach

With the aim of obtaining proper composite electrolytes, a systematic modeling analysis for the percentage increase in weight due to swelling with respect to swollen weight, S_w, and the room temperature conductivity (σ₂₅) of the composite films of polyethylene glycol based thermoplastic polyurethane/polytetramethylene glycol based thermoplastic polyurethane/polyethylene oxide [denoted as TPU(PEG)/TP-U(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 plot results show that both the maximum S_w (64.9%) and the maximum σ₂₅ (72.2 × 10^-5 S cm^-1) appear at point X₃ (PEO 85%, TPU(PEG) 15%). 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 by using differential scanning calorimeter. The crystallization of PEO spherulites at different compositions was examined by using a polarizing microscope.