Formation of Polyaniline and Related Polymers

In most reports that deal with electropolymerization of aniline and its derivatives, the formation of a cation radical or another intermediate in the initial stage of the process is assumed [191]. A basic reaction mechanism of the anodic oxidation of anilines 

Hambitzer and co-workers [215-218] reported the detection of soluble products of aniline electrooxidation by using electrochemi- 

The effect of the substitution on the reactivity of the monomer was studied in more detail recently [231]. The electrooxidation of a selection of N-alkyl-substituted (V-ethyl- and A7,V-dimethyl-) and ring-substituted (o-, m-, p-methyl-, o-ethyl-) aniline derivatives at no glass electrodes was investigated using UV-vis spectroscopy in sim (further details follow). With V-ethylaniline, well defined absorbance peaks of an intermediate and an end product were observed after an anodic potential step (Fig. 17). Conversion of the electrogenerated intermediate into an end product 

As already indicated the stabiUty with respect to the reactivity of the reaction intermediate(s) and the reactivity of the monomer are closely related. In a comparative study, the influence of various substituents on the reactivity of substituted anilines was investigated [239-241]. Slow film formation enabled the detection of two oxidation steps in cyclic voltammograms before the redox pro- 

Based on kinetic data of the investigated aniline oxidation reaction as obtained with a variety of methods, including spectro-electrochemical ones, numerous researchers [252-270] have proposed an autocatalytic mechanism of oxidation and growth. In this scheme, polymer growth occurs without further electrooxidation of aniline monomers. The polymer film in its oxidized form contains oxidized aniline imits, most likely also at the ends of polymer chains. These units react basically like monomeric radical cations with further monomer molecules from solution (radical cation-parent molecule coupling). Subsequently, the chain has to be reoxidized, that is, one electron has to be transferred per monomer unit. An alternative proposal is that pemigraniline sites act as oxidants for monomer units [271]. The characterization of this pro- 

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