Polyaniline doped with different sulfonic acids by in situ doping polymerization

Doped polyaniline (PANI) was synthesized by an "in situ doping polymerization" method in the presence of different sulfonic acids, such as methanesulfonic acid (MSA), p-methylbenzene sulfonic acid (MBSA), beta-naphthalenesulfonic acid (beta-NSA), alpha-naphthalenesulfonic acid (alpha-NSA), 1,5-naphthalenedisulfonic acid (1,5-NSA), and 2,4-dinitronaphol-7-sulfonate acid (NONSA). Morphology, solubility in m-cresol, and electrical properties of the doped PANI were measured with the variation of the molecular structure of the selected sulfonic acids. Granular morphology was obtained when the sulfonic acids without a naphthalene ring, such as MSA and MESA, were used. Regular tubular morphology was obtained only when beta-NSA was used. The tubular morphology can be modified by changing the substitutes, the number, and location of sulfo-group(SO3-H) on the naphthalene ring. These results indicated that naphthalene ring in the selected sulfonic acids plays an important role in forming the tubular morphology of the doped PANI by the "in situ doping polymerization" method. All resulting PANI salts were soluble in m-cresol, with the solubility depending on the molecular structure of the selected dopants. Room-temperature conductivity for the doped PANI ranges from 10(-1) to 10 degrees S/cm. Temperature dependence of conductivity shows a semiconductor behavior, and it can be expressed by one dimenson Variable Range Hopping (VRH) model. (C) 1999 John Wiley & Sons, Inr J Polym Sci A: Polym Chem 37: 1277-1284, 1999.