Electrochimica Acta 51 (2005) 1036–1043 Electrochemical and in situ TM-AFM studies of the polymerization conditions on poly(o-methoxyaniline) film morphology Marek Szklarczyk ∗ , Emil Wierzbi´ nski, Krzysztof Bie ´ nkowski, Marcin Strawski Laboratory of Electrochemistry, Department of Chemistry, Warsaw University, ul. Pasteura 1, 02-093 Warsaw, Poland Received 21 March 2005; received in revised form 31 May 2005; accepted 31 May 2005 Available online 7 July 2005 Abstract The in situ atomic force microscopy and the electrochemical studies on electropolymerization of the o-methoxyaniline in the 0.0–0.8 V versus NHE range of the electrode potential are described. It is proved that in the 0.0–0.3 V versus NHE a redox process takes place, resulting in the formation of poly(o-methoxyaniline) in its reduced form, leucoemeraldine. The different morphologies are exhibited by poly(o-methoxyaniline) under different polymerization conditions. The microscopic results show that with the increase of the monomer concentration in the bulk of electrolyte solution the globular morphology, related to the coil like molecular structure, is replaced by the fibrilar one, related to the opened-up, more conductive extended coil structure. It is shown that oxidation of a leucoemeraldine state of polymer to its emeraldine state results in the change of the morphology from the chain like structure to the massive fibrilar like structure. The reduction of oxidized polymer results in its irreversible fragmentation. © 2005 Elsevier Ltd. All rights reserved. Keywords: Electropolymerization; o-Methoxyaniline; Morphology; Platinum; In situ AFM 1. Introduction Over the past decades conjugated polymers have been a subject of intense interest in surface science [1]. In particular, more than a century-old polyaniline (PANI) [2–4] and its derivatives have attracted a significant attention owing to the straightforward preparation methods (e.g. [5–9]), good stability of the conductive form in aqueous solution [10,11] and multiple potential applications [12,13]. In order to obtain the most suitable material for particular use, physical, optical, chemical, electrochemical and morphological properties of the polymeric films have to be determined. Considering a large number of papers devoted to the research on electropolymerization mechanism of conducting polymers, much fewer papers have been published on their degradation and morphology changes in dependence on the experimental conditions like electrochemical potential, monomer concentration and reaction time. The degradation ∗ Corresponding author. Tel.: +48 22 822 0211; fax: +48 22 822 5996. E-mail address: szklarcz@chem.uw.edu.pl (M. Szklarczyk). degree and structure/morphology play a crucial function for such polymer properties like, e.g. conductivity [14–16]. The conductivity can be changed by orders in magni- tude only by playing with these two properties [17]. The conductivity of polyaniline in an ideal emeraldine form should be comparable to copper (i.e. 10 5 S cm -1 [18]). Yet, experimental conductivity does not exceed ∼5 × 10 2 S cm -1 [17]. Several reasons can be invoked to explain this discrep- ancy. Among the most important is structural heterogeneity, which influences the ideal sequence of benzenoid and quinoid rings (alternating two benzenoid and one quinoid ring units) in the emeraldine oxidation state. It can be related to the differences in the oxidation rates of benzenoid and quinoid units, which are polymeric film morphology dependent [19]. One of the explanations for the relation of electronic conductivity to morphology is a change in the real surface area of polymer resulting in higher number of centers for polymeric chain oxidation [20]. Morphology of the electrochemically growth polyaniline (PANI) and its derivatives, e.g. poly(o-methoxyaniline) (POMA) are strongly dependent on the experimental electrochemical 0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2005.05.044