Polymerisation and characterisation of conducting polyaniline nanoparticle dispersions

Micellar emulsion chemical polymerisation of polyaniline (PANI) using dodecylbenzenesulfonic acid (DBSA) as the micelle and dopant was performed at 20 °C. It was necessary to use a ratio of 1:1:1 for aniline, oxidant (ammonium persulfate APS) and DBSA to produce the PANI · DBSA in the emeraldine salt (ES) form in large quantities (40 g). The resulting polymer was a nanodispersion with spherical particles 10 ± 2 nm in diameter and an electrical conductivity of 15 ± 3 S cm−1 as determined by transmission electron microscopy (TEM) and the four-point probe method, respectively. UV–vis spectral characterisation showed the nanodispersion to be highly doped. Complete deprotonation of the polymer to the emeraldine base form using 0.5 M NaOH was only possible upon dilution to approximately 0.05% w/v polymer. Reduction of the polymer to leucoemeraldine using phenylhydrazine was relatively slow; however, oxidation to pernigraniline in 0.25 M APS occurred instantaneously.