COMPARATIVE SPECTROELECTROCHEMICAL INVESTIGATION OF VACUUM-EVAPORATEDAND ELECTROCHEMICALLY SYNTHESIZED ELECTROCHROMIC POLYANILINE FILMS

A spectroelectrochemical study of thin electrochromic polyaniline (PAN ) films deposited on SnO2 glass substrates by a vacuum thermal evapora tion method has been carried out. The films obtained were studied by m eans of spectral, spectroelectrochemical and electrochemical methods, and the results were compared with those obtained for PAN films prepar ed by electrochemical polymerization. Spectroelectrochemical data (obt ained under a potential step) and cyclic voltammetry data showed that the evaporated PAN films did not undergo a second oxidation stage resu lting in formation of a quinoid structure. Current vs. time dependence s processed according to the Cottrell equation showed that the diffusi on coefficient for the evaporated PAN layers was almost a factor of 3 lower than that for the electrochemically deposited films. During cycl ic tests in a real electrochromic optical filter the evaporated PAN la yers exhibited a stability more than 2.5 times higher than that of the electrochemically deposited films.