EFFECT OF PRIMARY DOPANTS ON THE CONDUCTIVITY OF POLYANILINE SYNTHESIZED BY ELECTROCHEMICAL POLYMERIZATION

Abstract

Polyaniline salts were synthesized at room temperature (300 C) by electrochemical oxidation using primary dopants such as HCL, HNO3, H2SO4 and CH3COOH. All the synthesized PANI have resulted in emeraldine salt form as indicated by dark green colour of the salts. Various characterization techniques employed were UV-Visible spectroscopy, FT-IR and Cyclic voltammetry studies. All these techniques confirm the various properties of PANI. The characteristic peaks in the UV-Visible spectra of the samples indicate that effective doping has occurred in the synthesized polymer polymers. Quinoid and benzenoid bands at 1553-1596 cm-1 and 1437 – 1496 cm-1 respectively were observed in all the samples. The band gaps for all the samples were obtained using the absorption spectra and Stern relation. PANI-H2SO4 had the least band gap whereas PANI-CH3COOH had the highest band gap. The voltammograph showed the various oxidation states during the electrochemical deposition at a potential of 0.8 V. Four probe Method was used to study the conductivity of both thin films deposited on ITO slides. The conductivity values for PANI-H2SO4 were found to be 3.424 S.cm−1 for thin film. By comparing the four samples’ π - π* transition, from the strongest to the weakest were in the order: , PANI-H2SO4 followed by PANI-HCl then PANI-HNO3 and the weakest been PANI-CH3COOH. This suggests that polaron charge carriers are responsible for the high conductivity in H2SO4 doped PANI.