Blends of poly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonate [NBR-PAni.DBSA] were Successfully prepared using an internal mixer for the first time. Electrical conductivities Of all the vulcanized blends (up to 10(-2) S/cm with a conductivity percolation threshold 6.0 wt %/5.4 vol % of PAni.DBSA) were not affected with the addition of dicumyl peroxide (DCP) as the Vulcanizing agent. The FTIR spectra of vulcanized NBR-PAni.DBSA blends resembled a superposition of the spectra of the raw materials, but with some notable peak shifts because of the changing intermolecular interactions between the polymers. Blends with <= 30 wt % of PAni.DBSA showed the best compatibility, i.e., with greatest peak shifts for their FTIR spectra and largest temperature shifts for their DSC recorded thermal events. The morphological studies (of both optical and transmission electron micrographs) showed that the thermomechanical mixing method had reduced the amounts of phase separation in all these NBR-PAni.DBSA blends. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3199-3208, 2009