Structure and properties of self-doped polyaniline

Summary form only given. Sulfonated Polyaniline (SPAn) with various sulfonation degrees (SD) has been synthesized by the reaction of polyaniline and concentrated sulfuric acid using silver sulfate as catalyst. Only when SD of the SPAn is over 45% can it be dissolved in dilute aqueous alkaline solution and display apparent self-doping property. The reversible conversion between SPAn and its ammonium salt, confirmed by in-situ UV-Vis and ESR, is another evidence for the self-doping property of SPAn. From the different self-doping behavior of SPAn and poly (o-aminobenzoic acid), it is concluded that the formation of relatively strong intra-molecular ionic bonds is responsible for the effective self-doping property. 4-Amino-2-sulfonic acid diphenylamine is synthesized through Ullmann condensation, and successfully electropolymerized in H/sub 2/O/CH/sub 3/ CN/Na/sub 2/SO/sub 4/ system. The resulted polymer is a typical alternative compolymer of aniline and m-amino-benzenesulfonic acid. The differences in FTIR spectra and cyclic voltamograms between SPAn and the above alternative copolymer indicate that the sulfonic acid groups are somewhat randomly distributed on the backbone aromatic rings.