In this study, several polyaniline samples were prepared by oxidative chemical polymerization using only aniline, (NH(4))(2)S(2)O(8) and HCl in aqueous media at room temperature for morphological studies by SEM (scanning electron microscopy). The results show that polyaniline nanofibers can be obtained by template-free oxidative chemical polymerization in a conventional low-pH acidic aqueous medium (pH similar to 0) at room temperature. The study indicates that it is crucial to employ a mild post-polymerization processing procedure, such as dialysis, to preserve the as-formed morphology of polyaniline nanofibers. Our study also suggests that polyaniline could adopt the nanofiber structure as its intrinsic morphology when it is synthesized in a simple oxidative chemical polymerization system consisting of only aniline, (NH(4))(2)S(2)O(8) and HCl in an aqueous medium at room temperature. (C) 2008 Elsevier Ltd. All rights reserved.