Copolymerizations of a self-doping monomer (o-aminobenzenesulfonic acid, SAN) and aniline (AN) in different molar ratios via the self-assembly process were conducted to prepare self-doping polyanilines (SPANIs). The morphology of SPANIs can be changed from microspheres and nanotube to coral reef like structures by simply increasing the molar ratio of the monomer (AN) to the dopant (SAN). The relationship among the AN to SAN molar ratio, the morphology, UV-Vis absorption behaviors, thermal stability, electrochemical behavior, crystalline density, and conductivity of self-doped PANIs are investigated. The nanostructures were strongly dependent on the AN to SAN mole ratio. UV-Vis absorption behaviors changed with increasing degrees of self-doping, which correspond to the various SPANI redox states. Moreover, the decomposition temperature was also relative to the degree of self-doping. A higher degree of self-doping led to higher SPANI degradation temperatures. oxidation and reduction current peaks occur at more positive potentials for SPANIs with a higher degree of self-doping. High crystalline density led to the high room temperature conductivity of the SPANIs, which was attributed to the interaction between the polymer chains. (c) 2008 Elsevier B.V. All rights reserved.