Electrode materials polyaniline electrochemical polymerization

Most 2,5-unsubstituted pyrroles and thiophenes, and most anilines can be polymerized by electrochemical oxidation. For pyrroles, acetonitrile,54 or aqueous55 electrolyte solutions are normally used, while the polymerization of thiophenes is performed almost exclusively in nonaqueous solvents such as acetonitrile, propylene carbonate, and benzonitrile. 0 Polyanilines are generally prepared from a solution of aniline in aqueous acid.21 Platinum or carbon electrodes have been used in most work, although indium-tin oxide is routinely used for spectroelectrochemical experiments, and many other electrode materials have also been employed.20,21... 

The use of conjugated polymer as membranes to separate various liquid mixtures has been reported in the literature [19,20], From those, polyaniline (PANi) is one of the most interesting and studied conjugated polymers. Polyaniline is usually prepared by direct oxidative polymerization of aniline in the presence of a chemical oxidant, or by electrochemical polymerization on different electrode materials [21,22], The possible interconversions between different oxidation states and protonated and depronated states [23], figure 4, make this material remarkable for different purposes. Under most conditions, PANi... 

Apart from the insulating polymeric matrices, conductive polymers such as polypyrrole and polyaniline have been used as nanocomposite electrodes by chemical or electrochemical polymerization [13, 17, 116, 117]. Such materials provide high conductivity and stability. However, the use of insulating polymers can be more advantageous than the conductive polymers when employed in cyclic voltammetry. 

The electrochemical stability of PAn film at higher potentials is essential for its use as an electrochromic material and as a catalytic electrode. Similarly, soluble polyaniline is also required for many applications to facilitate post-synthesis processing. Electrochemical polymerization can be carried out by 0.1 M monomer in 1 M of aqueous solution of aromatic sulphonic acid. Prior to polymerization, the solution should be deoxygenated by passing argon gas for 30 minutes. 

The electrochemical cell arrangement described for production of PPy (see Chapter 2) is applicable to the electropolymerization of polyaniline. The polymerization cell design is of equal importance for the preparation of polyaniline as for PPys. All the requirements of the cell design apply, and the same versatility of the form of assembly can be attained, although, in practice, polyaniline has not been investigated as extensively in this regard. The only additional requirement of a polymerization cell for polyaniline is that the electrode and construction materials should be stable in acid media. 

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