The Polymerisation of Aniline and Methylsubstituted Derivatives: Electrochemical and Spectroscopic Investigations

Abstract

Abstract During the potentiostatic polymerisation of aniline (ANI) and 2,6‐dimethylaniline (2,6‐DMA) we measured simultaneously the current densities i , the anodic charge q an , the redox charge q redox , 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.