In this study, biodegradable and conducting polyaniline-graft-chitosan (PAni-g-CS) copolymer was synthesized by radicalic polymerization using ammonium persulfate (NH4)(2)S2O8 as initiator. The synthesized copolymer was characterized by using particle size, density, band gap, H-1 NMR, TGA, and SEM measurements. The characterization results revealed the successful synthesis of the graft copolymer of PAni and CS. Electrokinetic properties and colloidal stabilities of PAni-g-CS dispersions were examined as a function of time, pH, electrolytes, various surfactants, and temperature by means of zeta-potential measurements in polar (water) and non-polar (silicone oil) media. The zeta-potential of PAni shifted to more positive region after grating with chitosan. In acidic medium, zeta-potential of the copolymer was observed to increase up to +44 mV. The presence of monovalent (Nacl) electrolyte had no impact on zeta-potential of the copolymer dispersions whereas; divalent (BaCl2) and trivalent (AlCl3) electrolytes caused the zeta-potentials of the dispersions to shift to more positive regions. The most effective surfactant on the zeta-potential of the PAni-g-CS was determined to be sodium dodecyl sulfate, which reduced the value of zeta-potential to -39 mV. Elevated temperatures caused almost no change on the zeta-potential of the copolymer dispersions. In non-aqueous media, zeta-potential of PAni-g-CS was found to be in colloidally stable region. Further, PAni-g-CS was tested against Escherichia coli and showed an improved antibacterial activity when compared to that of pristine PAni and CS. (C) 2014 Elsevier B.V. All rights reserved.