Polyaniline by new miniemulsion polymerization and the effect of reducing agent on conductivity

A new stable miniemulsion of aniline was prepared using sodium dodecyl sulphate (SDS) as the surfactant and cetyl alcohol as the cosurfactant. The oxidative polymerization reaction was initiated by ammonium peroxy disulphate (APS). At the end of the polymerization reaction polyaniline (PAni) formed was treated with stannous chloride (SnCl2) and finally doped with p-toluene sulphonic acid (PTSA). The monomer to oxidant and polymer to dopant mole ratio were optimized. Maximum conductivity is obtained with monomer to oxidant mole ratio1:1 and polymer to dopant mole ratio 1:0.5. There is a decrease in particle size and increase in the solubility in miniemulsion process. Dramatic increase in the conductivity is due to the treatment with SnCl2. Part of the pernigraniline (PNB) form of PAni formed was reduced by SnCl2 to emeraldine base (EB) form having higher conductivity. Plausible reduction mechanism with SnCl2 is proposed. The conduction mechanism is explained using EPR measurement. The reason for difference in conductivity of different forms of PAni is explained with the help of polaron formation and hole theory.