This work investigates the effect of different preparation routes including mechanical mixing and in situ polymerization of aniline on the electromagnetic interference shielding effectiveness (EMI SE) over the X-band (812 GHz) frequency range for polyaniline doped with dodecylbenzene sulfonic acid (PAni.DBSA) filled in styrenebutadienestyrene triblock copolymer matrix. The dc conductivity and dielectrical properties were also investigated. For all systems, the electrical conductivity, dielectric constant, and EMI SE increased with the increase in the concentration of PAni.DBSA. Blends prepared by the in situ polymerization exhibited higher conductivity and dielectric constant and better EMI SE characteristics than the physical blends with similar amount of PAni.DBSA. EMI SE value as high as -35 dB has been achieved with about 30% of PAni.DBSA prepared by the in situ polymerization. Regarding physical blends, those involving PAni.DBSA prepared by a redoping process displayed better EMI SE. For all systems under consideration, the conductivity and EMI SE bear an exponential relationship that can be represented by a master curve. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012