Oxidative polymerization reaction of the protonated form of aniline (ANI-HCl) was investigated experimentally in acidic
solutions with in situ spectrophotometric technique and computationally using molecular mechanics (MMC) calculations. Welldefined
absorbance peaks of an intermediate and of an end product were observed after first scan of the spectrogram, using zeroand
first-derivative spectroscopic treatment. Increases in the absorbance at lw420 nm with increasing the oxidant and/or anionic
surfactant (sodium dodecyl sulfate, SDS) content in the polymerization medium were observed. This indicates that the presence of
nitrenium cations and suggests that the polyaniline evolution goes towards a two-dimensional (D2) polymer with phenazine rings,
which can be formed by a cross-linking reaction. It was confirmed by kinetic studies, as well as verified by MMC calculations.
Absorbance peak at lw520 nm (dark brown), in the first scan of the spectrogram was observed. This peak increases with increasing
the acid surfactant [ poly(acrylic acid)] (PAA) matrix content in the polymerization medium. Kinetic parameters of the oxidative
polymerization reaction were deduced employing a computer-aided kinetic analysis of the absorbance (A) at w720 nm against
oxidation time (t) data. The results obtained indicate that the rate controlling process are governed by the two-dimensional (D2)
diffusion. Good linearity (rw0:985) between DH# and DS# for the series of acids doped PANI matrix was obtained, which suggests
the existence of a compensation (or isokinetic) effect. The proposed mechanism for the oxidation of ANI is also supported byMMC
calculation. Activation parameters for the rate of oxidation process of ANI have been computed and discussed.