In situ STM study of the counterion effect on the doping stages of polypyrrole films

The swelling (or deswelling) of a polypyrrole film due to the electrodoping has been investigated by scanning tunneling microscopy (STM) in order to correlate the surface morphological variations with the electroactivity of the film evaluated through its voltamperometric response. Different anions have been used and the results obtained show a remarkable correlation between the magnitude of topographical features and the film electroactivity according to the physicochemical nature of counterions. Moreover the inclusion of anions in the polymer matrix during the electrodoping induced strong morphological transformations in a micrometer scale. These experiments were performed in situ so as to reflect the solvation of the polypyrrole film and the counterions.