Mael Nicolas

Synthesis and properties of perfluorinated conjugated polymers based on polyethylenedioxythiophene, polypyrrole, and polyfluorene. Toward surfaces with special wettabilities.

The electrochemical deposition of organic materials is a convenient and straightforward method that affords rough films in mild conditions. The presence of fluorinated chains covalently attached on the polymer backbone allows the control of the second criterion which plays a role on the wetting properties of the surface, that is, the chemical composition. By modification of the nature of the polymer, films with different surface energies were obtained. Thus, original semifluorinated polypyrrole (PPy- RF n ), polyfluorene (PFl- RF n ), and polyethylenedioxythiophene (PEDOT- RF n ) have been chemically and electrochemically synthesized and characterized. On one hand, the chemical polymerization affords highly fluorinated soluble polymers. Soluble PFl- RF n exhibits blue fluorescence in solution while soluble PEDOT- RF n presents optical properties similar to those of PEDOT. Consequently, they represent interesting candidates for optical devices (OLEDs for PFl- RF n , electrochromic materials for PEDOT- RF n ). On the other hand, surface properties have been investigated on the electroformed polymers by goniometry and microscopy. Fluorinated surfaces of electrodeposited polypyrrole, like polythiophene, give birth to high hydrophobic and oleophobic surfaces, while the use of polyethylenedioxythiophene as the polymer increases sufficiently the surface energy to get combined superhydrophobicity and superoleophilicity. The influence of the chemical composition is discussed through the comparison of the wetting properties of polyethylenedioxythiophene and semifluorinated polythiophene and polyethylenedioxythiophene.

Acids and alkali resistant sticky superhydrophobic surfaces by one-pot electropolymerization of perfluoroalkyl alkyl pyrrole

Over the past few years, electropolymerization of semifluorinated monomers like thiophene or pyrrole has been used as a gentle and effective method to generate, in one step, stable superhydrophobic surfaces. The synthetic route mostly involves the coupling reaction between a carboxylic acid and an alcohol, using a carboxy group-activated reagent and a catalyst. As a consequence, the electroformed surfaces present high liquid repellency due to the concomitant effect of roughness and low surface energy. Nevertheless, the ester connector can be cleaved under acidic and basic conditions, preventing its use under a range of environmental conditions. To overcome this drawback, a new perfluoroalkyl alkyl pyrrole has been synthesized, the fluorinated segment being connected to the electropolymerizable part via an alkyl chain, and electropolymerized, leading to surfaces that exhibit a static contact angle with water superior to 150 degrees and no sliding angle, over a wide pH range and with a long lifetime. This represents the first example of a pure conducting polymer surface with sticky superhydrophobicity not only in pure water but also in corrosive solutions such as acids and bases, giving rise to new prospects in practical applications.

Fabrication of Superhydrophobic Surfaces by Electropolymerization of Thiophene and Pyrrole Derivatives

The electropolymerization of five-membered heterocycles like thiophene and pyrrole leads to the deposition of conductive and morphology-controlled films onto different kinds of electrodes. It involves many experimental parameters such as the chemical nature and concentration of the monomer and electrolyte, the solvent, the nature of electrode, the applied electrical conditions and the time considered. These electrosynthesis conditions determine to a large extent the structure, morphology and properties of the resulting polymer. By controlling them, it represents a straightforward method to obtain highly porous surfaces. The use of low surface energy alkyl or perfluoroalkyl chains together with the electropolymerization process allows the control of the two parameters that generally govern the wettability of a surface, i.e. the chemical composition and the microstructure of the surface, and affords an excellent method to reach very stable superhydrophobic surfaces with a low contact angle hysteresis.