Polymer Bulletin 45, 113-120 (2000) * Corresponding author Polymer Bulletin Springer-Verlag 2000 Preparation and characterization of fully oxidized form of polyaniline Nayana Chandrakanthi * , M. A. Careem Department of Physics, University of Peradeniya, Peradeniya, Sri Lanka Received: 10 May 2000/Revised version: 1 August 2000/Accepted: 1 August 2000 Summary The oxidation state of polyaniline (PANI) can be varied from the fully reduced leucoemeraldine base (LEB) to the half oxidized emeraldine base (EB) and to the fully oxidized form pernigraniline base (PNB). In this work, the synthesis and properties of the highest oxidation state of polyaniline, pernigraniline, in the base as well as the corresponding salt form are discussed. Introduction Throughout the literature, the PNB and LEB forms are considered to be insulating, whereas the half oxidized form, after protonation, has been found to be conducting [1- 3]. The PNB form has recently attracted significant interest because it is the only known polymer besides polyacetylene that is known to exhibit a two-fold degenerate ground state [4-6]. A preparation method for the fully oxidized PNB form was first suggested by Green and Woodhead [7]. Early work of these authors reports that the fully oxidized state of polyaniline is rather unstable and that it cannot be isolated in the dry form. However, in 1990, MacDiarmid et al. have reported the first synthesis and isolation of PNB as an analytically pure powder, and demonstrated the production of free-standing, flexible films of this material [8]. The method reported by these authors for the synthesis of pernigraniline base is based on the controlled oxidation of EB with m- chloroperbenzoic acid [8]. Leclerc et al. [9] were the first to show that the fully oxidized PANI can exist in two different forms, i.e., the uncharged pernigraniline base (PNB), and the protonated pernigraniline salt (PNS), as shown in Figure 1.