Electrochromic properties of vacuum-evaporated polyaniline films

The emeraldine base was deposited on SnO2 glass substrates in vacuum by thermal evaporation in the temperature range 275-325 degrees C. The as-deposited films differ dramatically from the native polyaniline and are formed by the reduction of oligoanilines with molecular weight about 1500. The cycling acid-base treatment of vacuum thermally deposited films gives rise to formation of polyaniline-like material. The property restoration of sublimed films is apparently determined by the restoration of 3D associates in the film body. Molecular structure defects in vacuum-deposited films are responsible for the lower rates of coloration/decoloration, the lower contribution to imine formation and irreversible injection of anodic charge under the first oxidation/reduction cycle. The lower imine concentration in sublimed polyaniline films results in more coloration/decoloration cycles.