Free radical scavenging activity of homo and copolymer of aniline and para-phenylenediamine prepared in ZnCl2 medium

• The homo and copolymer of Ani and pPDA had antioxidant activities on DPPH radicals.
• The antioxidant activity was confirmed by UV-visible spectrophotometry.
• The EIS was successfully used to interpret the antioxidant activity.

This study reports on the ability of homo and copolymer of aniline and para -phenylenediamine (pPDA) to act as antioxidants to free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). Both the homopolymer and copolymer of aniline and pPDA at different molar ratios are synthesized on composite graphite electrode in phosphoric acid containing 0.5 M zinc chloride. The antioxidant activity has been monitored using UV–visible spectroscopy. The spectra of reaction mixtures in methanol have indicated that the elimination of the DPPH radical is increased with increasing of mole fraction of pPDA monomer. This is also confirmed by electrochemical impedance spectroscopy which demonstrated that as more pPDA are available in the mole fractions, the scavenging of DPPH radicals becomes more efficient. Charge transfer resistance (Rct) value of polyaniline (PAni) film is 2 × 104 Ω, which is much larger than that of poly para-phenylenediamine (PpPDA).

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