A hybrid material of polyaniline doped with dodecylbenzenesulfonic acid and conductive carbon black (PaniDBSA/CB) was prepared by in situ polymerization. The presence of low amount of CB (up to 25 wt %) resulted in a decrease in resistivity as compared to pure PaniDBSA. Composite with 25 wt % of CB presented the lowest resistivity and a tubular morphology characterized by microtubules with high aspect ratio evidenced by SEM examination. Higher amount of CB give rise to materials with higher resistivity values and a granular morphology, similar to pure carbon black. Ultraviolet-visible and electron paramagnetic resonance analyses were employed to evaluate the polaron concentration. X-ray diffraction was used to characterize the molecular structure of these composites. It was observed a decrease in the crystallinity degree and a shift of the polaron band transition toward lower wavelength as the amount of CB in the composite increases. From the EPR measurements, one can suggest that the higher chain order and polaron mobility is observed in hybrid with 25% of CB. This behavior is in agreement to the electrical resistivity values and SEM microscopy. The effect of CB on thermal stability of the composites was also investigated. The effect of the PaniDBSA/CB hybrid material on the processability and resistivity of the composites based on styrene-butadiene-styrene (SBS) block copolymer as the insulating matrix have been also evaluated. (c) 2006 Wiley Periodicals, Inc.