4-(n-[4-(4-Nitrophenylazo)phenyloxy]alkyl]aminobenzene sulfonic acid (Cn-ABSA, where n = 2, 4, 6, 8, or 10) as a novel dopant for conducting polymers of polyaniline (PANI) was designed and synthesized. The molecular structure of Cn-ABSA was characterized with H-1 NMR, Fourier transform infrared, and secondary-ion mass spectrometry. Nanostructures (nanotubes or nanorods) of PANI-(Cn-ABSA) were successfully synthesized with a self-assembly process in the presence of Cn-ABSA as the dopant. The morphology (shape and size) and conductivity of the resulting nanostructures strongly depended on the number of alkyl groups (n) and, in particular, the addition of water before polymerization. The formed micelles of aniline/Cn-ABSA/water were proposed to be templatelike in forming PANI-(Cn-ABSA) nanostructures on the basis of the emulsion properties measured by dynamic light scattering.