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Polyaniline (PANI), poly(o-anisidine), and poly[aniline-co-(o-anisidine)] were synthesized by chemical oxidative polymerization with ammonium persulfate as an oxidizing reagent in an HCl medium. The viscosities, electrical conductivity, and crystallinity of the resulting polymers (self-doped forms) were compared with those of the doped and undoped forms. The self-doped, doped, and undoped forms of these polymers were characterized with infrared spectroscopy, ultraviolet-visible spectroscopy, and a four-point-probe conductivity method. X-ray diffraction characterization revealed the crystalline nature of the polymers. The observed decrease in the conductivity of the copolymer and poly(o-anisidine) with respect to PANI was attributed to the incorporation of the methoxy moieties into the PANI chain. The homopolymers attained conductivity in the range of 3.97 ϫ 10 Ϫ3 to 7.8 S/cm after doping with HCl. The conductivity of the undoped forms of the poly[anilineco-(o-anisidine)] and poly(o-anisidine) was observed to be lower than 10 Ϫ5 J/S cm Ϫ1. The conductivity of the studied polymer forms decreased by the doping process in the following order: self-doped 3 doped 3 undoped. The conductivity of the studied polymers decreased by the monomer species in the following order: PANI 3 poly[aniline-co-(o-anisidine)] 3 poly(o-anisidine). All the polymer samples were largely amorphous, but with the attachment of the pendant groups of anisidine to the polymer system, the crystallinity region increased. The undoped form of poly[aniline-co-(o-anisidine)] had good solubility in common organic solvents, whereas doped poly[aniline-co-(oanisidine)] was moderately crystalline and exhibited higher conductivity than the anisidine homopolymer.

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Polyaniline was chemically synthesized in aqueous acidic medium (HCl) with ammonium peroxydisulfate [(NH 4) 2 S 2 O 8 ] as the oxidizing agent, using a procedure described in the literature. Because the synthesis of polyaniline was carried out in aqueous acidic media, the obtained product consisted of emeraldine hydrochloride. The obtained product was washed several times with water and with HCl solution in which it was synthesized, and then treated with ammonia solution at room temperature overnight to convert it to the base form before doping. CuCl 2 , AlCl 3 , and ten different organic or protonic acids were examined as dopants in different conditions. We observed that washing of the product, the reaction time and synthesis conditions, the acidity of the reaction media, and the type and concentration of the doping agents all affected the conductivity of polyaniline. The best conductivity (∼ 27 S cm −1) was obtained by HBr at 0.5 M concentration.

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