The Effects of Dopant Acids on Structure and Properties of Poly(o-methoxyaniline)

Poly(o-methoxyaniline) (POMA) was chemically synthesized using ammonium persulfate (APS) as oxidant. Methane sulfonic acid (MSA), hydrochloric acid (HCl), and p-toluene sulfonic acid (pTSA) were used as dopants, under the same reaction conditions. For comparison, undoped POMA was also synthesized. The polymer samples were characterized by Fourier transform infrared spectroscopy (FTIR), four-probe conductivity measurement, scanning electron microscopy (SEM), electron spin resonance (ESR), gel permeation chromatography (GPC), and determination of specific surface area. The antioxidant activities of POMA were assessed via reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, and the anti-microbial activities were determined as minimum bactericidal concentrations against E. coli 25422 and S. aureus 6838. When doped with relatively strong acids, high yield (above 84%) was achieved, compared to the relatively low yield (45%) when no dopant was present. The conductivity decreased in the order POMA-pTSA > POMA-HCl > POMA-MSA > undoped POMA. A polaron conduction mechanism was supported by FTIR and ESR spectra. The morphology of the polymers was found to be effectively controlled by dopants. All POMA polymers showed strong free radical scavenging ability, which was highly correlated with the specific surface areas of the polymer particles. All the tested samples showed activity against S. aureus 6838, but not at the concentrations tested against E. coli 25422. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 353-361, 2012