Polyaniline (PANI), poly(o-anisidine), and poly[aniline-co-(o-anisidine)] were synthesized by chemical oxidative polymerization with potassium iodate as an oxidizing agent in a hydrochloric acid (HCl) medium. The self-doped, doped, and undoped forms of these polymers were characterized by infrared spectroscopy, ultraviolet–visible spectroscopy, and the conductivity method. The observed decrease ... [Show full abstract] in the conductivity of the copolymer and poly(o-anisidine) with respect to PANI was attributed to the incorporation of methoxy moieties into the PANI chain. The homopolymer attained conductivity in the range of 3.75 × 10−3 to 7.40 S cm−1 after doping with HCl. The conductivity of the undoped form of poly[aniline-co-(o-anisidine)] and poly(o-anisidine) was observed to be lower than 10−5 S cm−1. The conductivity of the polymer sample decreased in the following order: PANI → poly[aniline-co-(o-anisidine)] → poly(o-anisidine). The undoped form of poly[aniline-co-(o-anisidine)] had good solubility in common organic solvents.