Use of wood derivatives as doping / dispersing agents in the preparation of polypyrrole aqueous dispersions

Abstract

Polystyrene sulfonic acid (PSS), lignosulfonic acid (LS) sodium salts, and carboxymethylcellulose (CMC) were used as doping/dispersing agents in the chemical polymerization of polypyrrole (Ppy). Conductivity measure-ments performed on dry Ppy pellets showed a sharp increase in conductivity when adding the anionic polymers to the polymerization liquor. For a polyanion/pyrrole weight ratio ranging between 0.1 and 0.6, the highest conductivity was given by PpyCMC (82 S/m) and PpyPSS (80 S/m), followed by PpyLS (6 S/m). On the other hand, for a polyanion/pyrrole ratio higher than 0.6, the conductivity of PpyPSS systems sharply decreased, and for polyanion/pyrrole ratios higher than 1, the highest conductivity was given by PpyCMC (~10 S/m), followed by PpyLS (~7 S/m) and PpyPSS (~5 S/m). Zeta-potential measurements showed that the surface charge of Ppy was strongly affected by the polyanion type and amount. Cationic Ppy particles were obtained in the presence of the two polymers bearing strongly acidic moieties (PSS and LS). Anionic PpyPSS colloids were obtained at the highest PSS/Py ratio, after the degradation of the conducting properties. When using a weakly acidic dopant (CMC), PpyCMC colloids had a negative charge for all of the tested conditions.