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

摘要

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 undloped 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 X 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-(oanisidine)] was moderately crystalline and exhibited higher conductivity than the anisidine homopolymer.