EFFECT OF SULFONIC-ACID GROUP ON POLYANILINE BACKBONE

This paper, aimed at delineating the significant changes in polyaniline (PAN) upon going from external protonic doping to internal doping, describes results on preparation and characterization of a self-doped conducting polymer: sulfonic acid ring-substituted polyaniline (SPAN). This polymer has a wide range of solubility, which improves the processibility of the polymer. Elemental analyses and spectroscopic data show that approximately 50% of the total number of phenyl rings in the polymer are monosubstituted by -SO3- groups. SPAN has an intrinsic acid that is capable of doping the polyaniline backbone. Little correlation between the conductivity and pH is observed, the conductivity of approximately 0.1 S/cm being independent of pH for pH less than 7.5. Transport, magnetic, and electrochemical properties of SPAN provide insight into both the structural and electronic properties and the role that -SO3- and -SO3-Na+ groups play in affecting the solubility, doping mechanism, and charge transport in the polyaniline system. Comparative studies of SPAN and PAN show similarities due to the same backbone structure and differences because of the -SO3- groups on the phenyl rings.