Layer-by-layer assembly of poly(aniline-N-butylsulfonate)s and their electrochromic properties in an all solid state window

Layer-by-layer (LBL) self-assembly by sequential adsorption of a polyanion, poly(aniline-N-butylsulfonate)s (PANBUS), onto oppositely charged cation, vinylbenzyldimethyldodecylammonium chloride (VDAC), led to the formation of ultra thin films at indium–tin oxide (ITO) glasses. The building up of such multilayer films was characterized by the increment of the absorbance through UV–visible spectroscopy, which indicated a linear dependence of the absorbance on the number of deposition cycles from 1 to 11 bilayers. Atomic force microscopy (AFM) showed that the size of PANBUS platelets increases with the number of bilayers, to result in clumps of PANBUS bundles in the 11-bilayer PANBUS films. Electrochromic (EC) properties of the PANBUS film coated on an ITO glass in contact to an ion conducting polymer film were investigated. The ion conducting polymer films were prepared via photocross-linking reactions of methoxy poly(ethylene glycol) monomethacrylate with trially-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione in the presence of LiCF3SO3 and a photoinitiator. In situ spectroelectrochemical study showed reversible electrochromic response with optical contrast higher than 0.1 and response times of ∼10 s when the number of bilayers was less than 10. EC property in thicker PANBUS films, showing slower response, was related to the topological change in the LBL film.