New aspects of the low-concentrated aniline polymerization in the solution and in SiC nanocrystals dispersion

Results of the simultaneous in-situ UV-vis and open-circuit potential (OCP) monitoring of the low-concentrated aniline (An) polymerization in the presence of camphorsulfonic acid (CSA) suggested that during the induction period (IP) step a transition state formed, which probably included anilinium cation and the oxidant anion, antecedent to a propagation step. No aniline oligomers were registered at this stage but they appeared at the beginning of the propagation step under the investigation conditions. The moments of formation of insoluble pernigraniline phase and appearance of emeraldine units in the growing pernigraniline chains were ascertained by the comparison of kinetic and OCP profiles of the polymerization process both in the solution and in SiC dispersion water mediums. It is deduced that pernigraniline reduction by aniline molecules begins earlier than it is generally accepted (i.e., earlier than OCP maximum is reached) and probably in parallel to a continuing appearance of pernigraniline units even in the same chains that undergo the reduction. It was found that an addition of the SiC dispersion phase into the polymerization mixture accelerates differently all stages of the aniline polymerization. Finally, this polymerization process leads to the formation of polyaniline (PANI)-CSA shell with thickness in the range from 0.5 nm to a few nm at the SiC nanocrystals surface.