Degradation of polydopamine coatings by sodium hypochlorite: A process depending on the substrate and the film synthesis method

Polydopamine coatings are promising new versatile coatings able to be deposited on almost all kinds of materials. Such films synthesized either by oxygenation or by electrochemistry on indium tin oxide (ITO) and glassy carbon substrates, were degraded by an oxidizing sodium hypochlorite solution. Films were successively immersed in a sodium hypochlorite solution (1 g/L) during different times. The characterizations of film degradation were made by XPS spectroscopy and AFM. They confirmed a homogeneous degradation of polydopamine, due to an oxidation reaction. The influence of the synthesis method and the nature of the substrate on the polydopamine degradation were also studied in this paper: coatings deposited on ITO by oxygenation degrade much faster than those deposited on glassy carbon or by electrochemistry. This suggests that the adhesion of the polydopamine films and their stability is markedly dependant on the used substrate (ITO vs. glassy carbon) as well as on the deposition method (oxygenation vs. electrochemistry), whereas the film thickness reached during deposition is almost substrate independent. (C) 2012 Elsevier Ltd. All rights reserved.