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

Abstract This study reports on the ability of homo and copolymer of aniline and para -phenylenediamine ( p PDA) to act as antioxidants to free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). Both the homopolymer and copolymer of aniline and p PDA 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 p PDA monomer. This is also confirmed by electrochemical impedance spectroscopy which demonstrated that as more p PDA are available in the mole fractions, the scavenging of DPPH radicals becomes more efficient. Charge transfer resistance (R ct ) value of polyaniline (PAni) film is 2 × 10 4 Ω, which is much larger than that of poly para -phenylenediamine (P p PDA).