Polyaniline doped with different sulfonic acids by in situ doping polymerization

Doped polyaniline (PANI) was synthesized by an "in situ doping polymerizati on" method in the presence of different sulfonic acids, such as methanesulf onic acid (MSA), p-methylbenzene sulfonic acid (MBSA), beta-naphthalenesulf onic acid (beta-NSA), alpha-naphthalenesulfonic acid (alpha-NSA), 1,5-napht halenedisulfonic acid (1,5-NSA), and 2,4-dinitronaphol-7-sulfonate acid (NO NSA). Morphology, solubility in m-cresol, and electrical properties of the doped PANI were measured with the variation of the molecular structure of t he selected sulfonic acids. Granular morphology was obtained when the sulfo nic acids without a naphthalene ring, such as MSA and MESA, were used. Regu lar tubular morphology was obtained only when beta-NSA was used. The tubula r morphology can be modified by changing the substitutes, the number, and l ocation of sulfo-group(SO3-H) on the naphthalene ring. These results indica ted 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 d oping polymerization" method. All resulting PANI salts were soluble in m-cr esol, with the solubility depending on the molecular structure of the selec ted dopants. Room-temperature conductivity for the doped PANI ranges from 1 0(-1) to 10 degrees S/cm. Temperature dependence of conductivity shows a se miconductor behavior, and it can be expressed by one dimenson Variable Rang e Hopping (VRH) model. (C) 1999 John Wiley & Sons, Inr J Polym Sci A: Polym Chem 37: 1277-1284, 1999.