Effect of the Electrosynthesis Method on the Surface Morphology of the Polypyrrole Film An Atomic Force Microscopy Study

The surface morphology of polypyrrole (ppy) films prepared by potentiostatic and voltammetric methods at the platinum electrode was studied by ex situ atomic force microscopy (AFM). The study was mainly focused on the early stages of polymer film growth up to a film thickness of 30 to 50 nm. AFM analysis revealed that polymer film morphology depends on the electrosynthesis method used. Electrosynthesized films produced by the voltammetric method consisted of nano-size ppy nodules, which during the polymer oxidation process become associated forming larger surface aggregates. However, in thicker films and those prepared using a large anion, this association was not observed. The ppy films formed by the potential step method (potentiostatic) allowed a better control of the early stages of the electropolymerization process. Thus, the AFM study showed that the first ppy nodules grow three-dimensionally during the application of the potential pulse steps, and simultaneously their number increase on the electrode surface according to the progressive nucleation and growth model. Negligible association of ppy nodules was noticed for the film prepared by the potentiostatic method, which suggests that this synthesis method is a better alternative for controlling ppy film growth.