Synthesis, characterization, and comparison of self‐doped, doped, and undoped forms of polyaniline, poly( o ‐anisidine), and poly[aniline‐ co ‐( o ‐anisidine)]

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 × 10 −3 to 7.8 S/cm after doping with HCl. The conductivity of the undoped forms of the poly[aniline‐ co ‐( o ‐anisidine)] and poly( o ‐anisidine) was observed to be lower than 10 −5 J/S cm −1 . The conductivity of the studied polymer forms decreased by the doping process in the following order: self‐doped → doped → undoped. The conductivity of the studied polymers decreased by the monomer species in the following order: PANI → poly[aniline‐ co ‐( o ‐anisidine)] → 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 ‐( o ‐anisidine)] was moderately crystalline and exhibited higher conductivity than the anisidine homopolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006