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During the potentiostatic polymerisation of aniline (ANI) and 2,6‐dimethylaniline (2,6‐DMA) we measured simultaneously the current densities i, the anodic charge qan, the redox charge qredox, the electrode capacity C, the average thickness d̄ of polymer and the absorption. ANI shows a delayed nucleation with a following autocatalytic polymerisation with hemispherical growth. The polymerisation of 2,6‐DMA takes place after a short period of nucleation. Then it grows homogeneously with a decreasing rate. Finally polymerisation is inhibited by termination reactions after a short period of nucleation. – The thickness of the interfacial double layer d′ is determined by capacity measurements to be d′PANI = 0.4 nm and d′P‐2,6‐DMA = 4 nm. – The Electrochemical Quartz Micro‐Balance (EQMB) yields the thickness d̄ of the total polymer layer, >400 nm in the case of PANI and about 40 nm for P‐2,6‐DMA after 3600 s. The number of electrons z exchanged during a redox cycle per monomer unit can be derived to about 0.1 for PANI and about 0.05 for P‐2,6‐DMA. – Because of a small torsion angle between the aniline rings the electronic conductivity of polyaniline (PANI) is high and the redox charge > 10% of the theoretical charge corresponding to 1 e‐/monomer. The torsion angle of poly‐2,6‐dimethylaniline (P‐2,6‐DMA) is high. Therefore the electronic conductivity is low and the redox charge < 5%. – The stoichiometric and other properties of the polymer films were investigated with XPS.

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