Ionic conductivity of polymer electrolytes derived from various diisocyanate-based waterborne polyurethanes

Various diisocyanate-based waterborne polyurethanes (WPU) were synthesized by polyaddition of poly(propylene glycol) (PPG) and dimethylol propionic acid (DMPA) with various diisocyanates ((4,4'-methylenebis(phenyl isocyanate) (MDI), 4,4'-methylenebis(cyclohexyl isocyanate)(H₁₂MDI), isophorone diisocyanate (IPDI), and toluene diisocyanate(TDI) via our modified acetone process. Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and impedance spectroscopy (IS) were utilized to monitor the phase change and the conductivity of the WPU-based electrolytes with the doped lithium perchlorate (LiClO₄) concentration. The soft segment T(g) increases with increasing LiClO₄ from the examination of DSC. Significant changes occur in the FTIR spectrum of the various diisocyanate-based WPUs with adding LiClO₄, indicating that different interactions with the lithium cation within the hard segment and between the hard and soft phases occur. The result reflects that the phase separation of aromatic diisocyanate-based WPU is more significant than that of aliphatic one in the addition of salts. IS results indicate that there exists the different effect of the added lithium salt on conductivity for aromatic/aliphatic diisocyanate-based WPU electrolytes. (C) 2000 Elsevier Science Ltd. All rights reserved.