An aqueous dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT) was prepared using a partially sulfonated poly(styrene-b-butadiene-b-styrene) (s-SBS) as a polyanion. For the preparation of s-SBS., poly(styrene-b-butadiene-b-styrene) was sulfonated to four different levels ranging from 44.1 to 64.8 mol%. These sulfonated polymers were characterized with IR spectroscopy and H-1 NMR analysis to confirm sulfonation reaction. The preparation of the PEDOT complex was carried out through the chemical polymerization method in which the EDOT monomer starts to polymerize in the presence of s-SBS, resulting in an aqueous dispersion of PEDOT/s-SBS complex. The DC conductivities of PEDOT/s-SBS complexes were found to increase from 0.0003 to 0.05 s/cm as the sulfonation level of the corresponding s-SBS increases, which is consistent with the data recorded by UV-vis spectrophotometer. From the XPS experiments, it was concluded that the concentration of PEDOT-rich phase in the PEDOT/s-SBS increases as the sulfonation level of s-SBS increase, thus facilitating the charge transport along the doped PEDOT chains. (C) 2008 Elsevier B.V. All rights reserved.