Molecular assembled self-doped polyaniline copolymer ultra-thin films

A self-assembly technique and copolymerization were used to buildup a self-doped polyaniline (SPANI) ultra-thin film on an indium-tin oxide (ITO) substrate. The monomers used were aniline and its derivative MSAN (m-aminobenzenesulfonic acid). Successful MSAN/AN copolymerization and film formation were simultaneously performed in aqueous solution with the addition of oxidant (APS, ammonium persulfate). The film deposition rate of a high AN/MSAN ratio system is generally higher than that of a low AN/MSAN ratio system. Cyclic voltammetry, UV–vis spectroscopy, and α-step instruments indicate a systematic dependence of the film thickness of these ultra-thin films on the assembly time and temperatures. The Auger depth profile reveals the elemental distribution in these films and exhibits different deposition rates between AN and MSAN. XPS N1s spectra also show the variation of the degree of doping. This SPANI film can be used as an electrochromic electrode in a corresponding device. Carboxyl-terminated-butadiene-acrylonitrile (CTBN) blended with LiClO4 was used as a solid polymer electrolyte. A total solid electrochromic device was assembled as ITO/SPANI/LiClO4–CTBN/PEDOT:PSS/ITO, where PEDOT:PSS is poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) as the counter complementary electrode. The device was pale gray at −1.5 V and blue at +1.5 V.