Polyaniline Emeraldine Salt Synthesis and Characterization: Effect of Aniline/Oxidant Molar Ratio and Acid Dopant Type and Concentration

Polyaniline (PANI) is considered one of the essential polymers due to its conductivity, affordable price, and high degree of stability, so it is successfully applied in several vital and strategic sectors, e.g., sensors, solar cells, fuel cells, and membranes. Polyaniline was synthesized by chemical polymerization using aniline monomer, ammonium peroxydisulfate (APS) as an oxidant and different mono, di, and tri-protonic acids, such as HCl, H2SO4, and H3PO4, respectively, as dopants. Each dopant was added using different concentrations from 0.5 to 2 M. The effect of dopant concentration on both polymer productivity and conductivity was investigated. X-Ray diffraction analysis (XRD) and Fourier-transform infrared spectroscopy (FTIR) were used to confirm the formation of PANI in the form of conductive emeraldine salt. The electrical conductivity of the synthesized polymer was also measured using a broadband dielectric spectrometer. The results revealed that the productivity and conductivity of PANI varied using different types of acids. The highest conductivities, 36.20, 74.80, and 49.30 mS/cm, were detected at concentrations 1.5 M HCl, 0.5 M H2SO4, and 2 M H3PO4, respectively. Empirical correlations were established using regression analysis to relate the oxidant-to-aniline (O/AN) molar ratio and acid concentration effects on PANI conductivity and productivity, demonstrating considerable effectiveness.