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Charge Transport Study in Para-Toluene Sulfonic Acid Doped Polyaniline

R.Ratheesh and K.Viswanathan

Polyaniline doped with PTSA in three different concentrations are prepared by chemical synthesis method and their thermal conductivity and electrical conductivity are measured. It is seen that the electrical conductivity increases linearly with temperature, showing the semiconducting nature of the sample. Also, the conductivity is maximum for highest doping concentration. The electrical conductivity is found to increase with increase of temperature, suggesting its thermal stability. The elemental analysis is carried out in order to understand the composition of the polymer with various elements such as C, H, N and S present in the doped samples. The higher value of %S in the sample having maximum level of doping(y=0.5) and conductivity, shows the effective doping of polymer chain. Also the %S decreases with decrease in the doping level (y=0.3 and y=0.1) which shows conductivity lower than that having maximum level of doping. The energy gap decreases with increase in doping level and thereby conductivity increases. Mott’s variable range hopping method is used to explain the conductivity behaviour. A detailed study has been made on the electron transport properties of PTSA doped polyaniline in the temperature range of 300 - 400 K. It is seen that there is more than one mechanism involved in charge transfer in polyaniline depending on the temperature range. Charge transfer in PANI is peculiar, so that no one mechanism can completely describe it. However, to some extent, conduction in polyaniline can be explained in terms of Mott’s three dimensional variable range hopping model, Kivelson model and Arrhenius model.