Novel electrochromic devices based on composite films of poly(2,5-dimethoxyaniline)-waterborne polyurethane

Waterborne polyurethane (WPU) was spin-coated on indium tin oxide (ITO) coated glass. Poly(2,5-dimethoxyaniline) (PDMA) was deposited using electrochemical polymerization as conducting composite film on the above WPU/ITO electrode and used as an electrode in an electrochromic device assembly. Tungsten oxide (WO₃) coated ITO glass was used as the other electrode with LiClO₄ doped gelled polyethylene oxide (PEO) as polymer electrolyte. The configuration of an electrochromic device was assembled: ITO/WPU-PDMA∥LiClO₄-PC-PEO (400,000)∥WO₃/ITO, where PC represents propylene carbonate. The characterization of the single electrodes, ITO/WPU-PDMA composite, ITO/WO₃, and the device was performed by using cyclic voltammetry. The columbic efficiency (CE) of the ITO/WPU-PDMA composite and ITO/WO₃ electrodes were close to 100%. The optical contrast of the single electrodes and the device were determined by UV-vis spectroelectrochemical studies. A visible contrast in color upon switching the potential from -1.50 to +1.50 V was noticed for the device. The device was pale yellow at -1.5 V and dark green at +1.5 V. The CE of the device was 91%. Double potential chronamperomtry was used to determine the response time of coloring and bleaching processes. The bleaching process was found to be faster than coloring. The stability of the device was established by polarizing the device and recording the UV-vis spectrum in open circuit conditions. Bleaching state is more stable than coloring state.