Studies on electrochemically synthesized polyaniline and its copolymers

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Date
2009
Authors
Parsa, Ali
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Abstract
Oxidative electropolymerization of aniline in phosphoric acid on 2B pencil composite graphite was accomplished using some selected inorganic salts as supporting electrolytes. These salts determined the degree of conductivity of polyaniline formed, in the order of CaCl2 > KCl > ZnCl2 > ZnSO4 > Ca3(PO4)2. The presence of either 0.06 M Ca3(PO4)2 or 0.2 M ZnSO4 in the synthesis of polyaniline have caused the shifting of its redox peaks as much as 250 mV to the negative potential. The shifting of these peaks was only influenced by type of anions presence not the cations. This incident has prompted the formation of copolymer aniline and ortho-phenylenediamine. The morphology of the homopolymer polyaniline films was also examined by a field emission scanning electron microscope and energy dispersive X-ray diffraction. The results showed that surface morphology of the homopolymer was dependent on the electrolytes used. The surface morphology also dictated each inorganic salt into different bloom-like crystal formations. The homopolymer synthesised in different salts has its antioxidant capacity increased. The phosphate medium polyaniline was a strong reducing agent, capable of scavenging 1,1-diphenyl-2-picrylhydrazyl radical in methanol. It was twice more effective as an antioxidant than the chloride medium polyaniline. The anodic homo and copolymerization of aniline and pyrrole on composite graphite in aqueous para-toluene sulphonic acid with and without potassium chloride (KCl) were investigated. The presence of KCl in the medium has improved the structural, optical and morphological properties of the resulting polymers. The X-ray photoelectron spectroscopy confirmed that poly(aniline-co-pyrrole) synthesized in the presence of KCl has nearly equal units of both pyrrole and aniline in the polymeric backbone as compared to the one synthesized in absence of KCl. The inherent negative shift of redox peaks of polyaniline has also been investigated in the copolymerization of aniline and ortho-phenylenediamine on composite graphite. The poly(aniline–co–ortho-phenylenediamine) modified composite graphite showed excellent electro catalytic response towards the oxidation of ascorbic acid. The anodic peak potential of ascorbic acid has been shifted from +0.5 V vs. Ag/AgCl (at bare composite graphite) to +0.1 V vs. Ag/AgCl (at poly(aniline–co–ortho-phenylenediamine) modified composite graphite), indicating easier electrode process of ascorbic acid on the later.
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PhD
Keywords
Chemical science , Electrochemically , Synthesized polyaniline , Copolymers
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