Polyaniline electroactivity

The electrochemistry of polyaniline is more complex than that of other conducting polymers and given the large number of possible structures for the material, it is not surprising that many possible reaction schemes have been suggested [181,182, 195-197,205], Many of the properties of the material are pH-dependent [173,174, 206], including the open circuit potential [207] which is most positive at pH 0, and this is further complicated by the fact that not all the polymer chains are necessarily in exactly the same state at any given time [197]. Above pH 3 polyaniline films do not show any electroactivity, but are not electroactive even at low pH with... 

The synthesis of polyaniline and copolymers of aniline with o-nitroaniline is aimed at obtaining an electroactive material. This material can be used, for example, as an electrode in conjunction with the magnesium electrode to construct chemical power sources. The polymers were prepared by oxidation of aniline or its mixture with nitroaniline ammonium persulfate in aqueous hydrochloric... 

Two nitrogen-containing electroactive polymers, polypyrrole (PPY) [21] and polyaniline (PAN) [22], have been of particular interest because of their environmental stability, high electrical conductivity and interesting redox properties associated with the chain heteroatoms. More importantly, PAN has been found to exhibit solution processability [23, 24] and partial crystallinity [25,26]. 

In considering the potential applications of electroactive polymers, the question always arises as to their stability. The deterioration of a physical property such as conductivity can be easily measured, but the chemical processes underlying it are not as easy to be revealed. In order to understand them, XPS has been used to follow the structural changes which occur in the polymer chain and the counter-ions of the doped polymer. The following sections present some XPS findings on the degradation of electroactive polymers, such as polyacetylene, polypyrrole, polythiophene and polyaniline, in the undoped and doped states. 

Intercalation of electroactive polymers such as polyaniline and polypyrrole in mica-type layered silicates leads to metal-insulator nanocomposites. The conductivity of these nanocomposites in the form of films is highly anisotropic, with the in-plane conductivity 10 to 10 times higher than the conductivity in the direction perpendicular to the film. Conductive polymer/oxide bronze nanocomposites have been prepared by intercalating polythiophene in V2O5 layered phase, which is analogous to clays. °° Studies of these composites are expected not only to provide a fundamental understanding of the conduction mechanism in the polymers, but also to lead to diverse electrical and optical properties. 

Until now, for methanol oxidation the best bimetallic catalyst was found to be Pt-Ru. Several papers deal with the electro-oxidation of methanol at Pt-Ru bimetallic system dispersed in polyaniline [33,46]. From results with bulk alloys, the optimum Pt/Ru ratio of around 6 1 to 4 1 was found [49] and confirmed [50]. The electroactivity of Pt-Ru-modified polyaniline is much better than that displayed by pure Pt particles dispersed into the PAni film. The optimum composition of the Pt-Ru bimetallic system was confirmed from these results [33]. The decrease of the poisoning phenomenon is the consequence of a low coverage in adsorbed CO resulting from the chemisorption of methanol. This was checked by considering the oxidation of CO at the same Pt-Ru/PAni-modified electrode [34], which occurs at low overvoltages (150 mV) in the presence of Ru. 

Conducting electroactive polymers (CEPs) such as polypyrrole, poly thiophene, polyaniline, and sulfonated polyaniline (1-4 shown subsequently) are complex, dynamic structures that captivate the imagination of those of us involved in intelligent material research.1 2 3 4 5... 

As with polypyrrole (PPy), the electrical, chemical, and mechanical properties of polyaniline (PAn) are inextricably linked. In addition, PAn has spectacular optical and chromic properties that distinguish it from other conducting electroactive polymers (CEPs). The current state of knowledge concerning properties of PAn is reviewed in this chapter. 

In 1985 David DeBerry [107], reported for the first time a change in corrosion behaviour of stainless steel with an electroactive polyaniline coating. He deposited polyaniline electrochemically from a pHl.O perchloric acid solution onto stainless steel and concluded that the coating was deposited over the passive metal oxide film (present on the metal surface in an acid environment). 

H. R. Ghenaatian, M. F. Mousavi, S. H. Kazemi, and M. Shamsipur, Electrochemical investigations of self-doped polyaniline nanofibers as a new electroactive material for high performance redox supercapacitor, Synth. Met., 159, 1717-1722 (2009). 

M. Malta, G. Louam, N. Errien, and R. M. Torresi, Nanofibers composite vanadium oxide/ polyaniline synthesis and characterization of an electroactive anisotropic structure, Electrochem. Commun., 5, 1011-1015 (2003). 

Ternary composites with electroactive components were also discussed by Gomez-Romero and coworkers in one of their recent publications [48]. The ternary composites consisted of doped-polyaniline (PANI) or doped-polypyrrole (Ppy) intercalated into V2O5 xerogels. The dopant anion for the conducting polymers was [Fe(CN)g] (HCF), derived from H3Fe(CN)6. More specifically, the synthesis of Ppy/HCF/V205 and PANI/HCFA 20s was carried out by treating the monomer (aniline or pyrrole)... 

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