Electroactive polyaniline films

Diaz, A.F. and J.A. Logan. 1980. Electroactive polyaniline films. J Electroanal Chem 111 111-114. 

A. F. Diaz, J. A. Logan, Electroactive polyaniline films, Journal of Electro-analytical Chemistry 1980, 111, 111. 

It was observed that the peak current increased with the number of potential cycles. This indicates that an electroactive polyaniline film was deposited onto the gold surface. The anodic peak at 0.91 V (peak D) has no corresponding cathpdic peak on the cyclic voltammograms, which means that this anodic peak refers to the oxidation of the aniline monomer to produce polymiline. Another three anodic peaks were observed at 0.2 V (peak A), 0.49 V (peak B) eind 0.76 V (peak C) respectively, and these peaks also increased with the number of potential cycle. This indicates oxidation of the deposited polyaniline on the gold electrode [20,21]. The three cathodic dips (dips A , B and C ) are due to reduction of polyaniline as also shown in the figure. 

Electroactive polyaniline films were synthesized by the catalysis of biUru-bin oxidase (BOD, a copper-containing oxidoreductase). The polymerization of aniline was carried out on the surface of a sohd matrix such as glass sUde, plastic plate, or platinum electrode to form homogeneous films [33]. The BOD was immobilized on the surface by physical absorption. The optimum pH was around 5.5. Some aniline derivatives such as p-aminophenol and p-phenylenediamine were good substrates for BOD. Structural analysis suggested the BOD synthesized polyanihne possessed partially 1,2-substititued structures. Cyclic voltammetric studies demonstrated that the PANl films were electrochemically reversible in redox properties, but differed from that of chemically or electrochemically synthesized PANl. The difference was attributed to the partial 1,2-substitution. Laccases are known to oxidize phenolic compounds in nature in the presence of oxygen and are capable in polyaniline synthesis in vitro [34-36]. 

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... 

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). 

Aleshin, A. N., Mironkov, N. B., Suvorov, A. V., Conklin, J. A., Su, T. M., and Kaner, R. B., Electrical properties of ion implanted and chemically doped polyaniline films, in Materials Research Society Symposium Proceedings on Electrical, Optical and Magnetic Properties of Organic Solid State Materials III, Vol. 413, 1996, p. 609. Cameron, D. A., and Reynolds, J, R., Conducting molecular composites of polypyrrole with electroactive polymeric dopant ions, ACS Proc., 37, 684 (1996). 

On the other hand, the polymerization using sulfonated polystyrene (SPS) as template produced the electroactive form of polyaniline (297-299). The resulting polymer was soluble in water and the conductivity reached 5x 10 S-cm without doping. Besides SPS, a strong acid surfactant, sodium dodecylbenzenesulfonic acid, provided suitable local template environments leading to the formation of conducting polyaniline. Aniline was also polymerized by BOD catalyst to give the polyaniline film, which was electrochemically reversible in its redox properties in acidic solution (300). 

This situation becomes complicated at higher potentials where a fully oxidized state hydrolyses to give soluble, electroinactive species. Polyaniline film loses its electroactivity above pH 5. 

BOD was entrapped in the enzymatically synthesized polyanQine film and the enzyme in the film was still active. Therefore, it is expected that this enzymatic synthesis of polyaniline film can be applied in the preparation of electroactive and enzyme-immobilized membranes on various solid matrixes. 

Chitosan modified with cellulose has been used to produce electroactive actuator films, since cellulose exhibits a piezoelectricity effect, which is conferred to the chitosan-cellulose composite (Kim et al., 2007b). Chitosan modified with polyaniline has also been demonstrated as an actuator that allows two actuation modes (Spinks etal., 2007). 

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. 

A polyanrline-poly(butyl acrylate-vinyl acetate) composite exhibiting electroactivity and having a conductivity of 2.2 S/cm was prepared by emulsion polymerization. The composite was soluble in common organic solvents and a stable water-based dispersion could also be prepared. Films cast from aqueous media had exceptional mechanical properties and had excellent adhesion to steel [144]. From the same group, a polyaniline and polyvinyl alcohol electroactive composite has been synthesized by... 

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