Different superhydrophilic polypyrrole nanostructures can be electrosynthezised in the presence of anions of weak acid (monohydrogenophosphate) and non-acidic anions (perchlorate) without the need for templates. Actually the type of nanostructures formed depends both on the concentration of anions at the electrode and on the interfacial pH. Depending on the anion composition of the pyrrole aqueous solution the film electrogenerated under a given applied potential is either a very thin membrane (10-20 nm) consisting of overoxidized polypyrrole or a tridimensional film with oriented nanowire array or a network of more or less interconnected nanofibers. The formation of such nanostructures is explained by a side reaction which is water oxidation. Since this reaction is pH-dependent, the pH of the pyrrole solution is one of the key parameter for the synthesis of such nanostructures. The reaction mechanism is discussed and compared to those proposed in the literature for nanofiber network electrosynthesis.Actually in the monomer solution, the role of the anions of weak acid is twofold. On the one hand they allow to limit the decrease of the interfacial pH during pyrrole oxidation and on the other hand to decrease the interfacial anion concentration, so that water oxidation takes place with formation of hydroxyl radicals and dioxygen nanobubbles.

Oxide polypyrrole (PPy) composite films have been studied as protective coatings for iron. PPy films, containing strong oxidative species like oxide, have been obtained in order to maintain the polymer in its oxidized state which corresponds to the iron passive domain. Oxide particles in suspension in pyrrole/tetraoxalate solution have been embedded in PPy film during its electrodeposition. The films have been characterized by electrochemical quartz crystal microbalance, scanning electron microscopy, transmission electron microscopy, and tested in 3% NaCl corrosive medium. A significant improvement of the protection efficiency was obtained with PPy/iron oxide composite films and especially with normalPPy/Fe3O4 composite films. © 2002 The Electrochemical Society. All rights reserved.

of polypyrrole nano/micro structures using an electrogenerated oriented polypyrrole nanowire array as framework. Electrochimica Acta, Elsevier, 2018Elsevier, , 268, pp.66 -72. <10.1016Elsevier, /j.electacta.2018.02.092>. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT AbstractThe purpose of this paper is to show that it is possible to increase the diameter and the length of the nanostructures of a framework formed of oriented polypyrrole nanowires that has been prepared by a templateless electrochemical method based on the use of a pyrrole solution containing a high concentration of weak-acid anion and a low concentration of non-acidic anion. The dimensions of the initial nanowires are increased by performing an additional electrosynthesis in a 'classical' monomer solution. Depending on the polarization time of this last synthesis (a few tens of seconds), wires with various diameters, from one hundred up to several hundred nanometers, are obtained. In addition to the variation of the nanowire size, these findings confirm, as outlined in the reaction mechanism we have proposed, that the base of the nanowires is surrounded by a thin non-conductive polymer i.e. by an overoxidized polypyrrole film. Actually this paper shows a proof-of-concept. Indeed one can imagine that the second polymeric electrodeposit could be performed using an organic monomer solution, using functionalized pyrrole monomer to fabricate a biosensor having large specific area, and/or using anions which could be drugs.