Investigation of vapor-deposited polyaniline thin films

X-ray photoelectron spectroscopy (XPS) has been used to investigate the chemical structure of thin polyaniline films grown using a vacuum evaporation process that used chemically prepared polyaniline powder as the starting material, Analysis shows that the as-deposited films are in the completely reduced, leucoemeraldine state. This chemical structure is contrasted with that of the initial and residual powders, which XPS analysis shows are both in a state close to that of protoemeraldine. Thus, the results indicate that the reduction takes place either in the gas phase or, more likely, as a reaction on the surface of the substrate, but does not occur in the quartz crucible as the initial powder is being heated. Results are also presented concerning the oxidation (in pure oxygen and iodine environments) and the protonation (using HCl) of these vapor-deposited polyaniline thin films. Scanning tunneling microscopy was also used to examine the in situ growth of submonolayer coverages of polymer. Evidence for large scale structure growth, possibly resulting from crosslinking of small oligomer components, was observed.