Structural changes in polyaniline upon reaction with DPPH

Polyaniline (PANI) powder was prepared using ammonium persulfate (APS) as the oxidant with an APS to aniline (ANI) ratio of 1.5. The powder was then reduced by hydrazine or dedoped using an aqueous ammonium solution. The antioxidant properties of these polymers were investigated through their reaction with the stable and intensely coloured DPPH radical. The highest DPPH scavenging activity was shown by reduced PANI, followed by PANI as-prepared, with the least radical scavenging shown by dedoped PANI. The reaction of PANI and DPPH radicals causes structural changes in PANI, with a transformation of-NH-and N⁺ groups to-N=.