Polyaniline prepared in the presence of various acids:: a conductivity study

Polyaniline (PANI) was prepared by the oxidation of aniline in the presence of various inorganic and organic acids at 20degreesC and -50degreesC. When strong acids were used, the conductivity of the protonated PANI was typically 1-10 S cm(-1). The results indicate that the protonation of PANI in media containing carboxylic acids was achieved with the help of sulfuric acid produced during the reaction with ammonium peroxydisulfate. The conductivity of PANI prepared under such conditions was reduced. Partial benzene-ring sulfonation has been proposed to explain the wide range in conductivity of PANI bases, 10(-11)-10(-7) S cm(-1). The densities of the samples reflect the nature of the acid used. The densities of the corresponding PANI bases exhibit much less variation. Molecular weight and degree of crystallinity of PANI are higher when the polymerization is carried out at -50degreesC. The conductivity of the PANI is determined mainly by way of protonation. The effects of molecular weight and of crystallinity on PANI conductivity are marginal. (C) 2004 Society of Chemical Industry.