Controlling electrodeposited conducting polymer nanostructures with the number and the length of fluorinated chains for adjusting superhydrophobic properties and adhesion

Abstract

Controlling the formation of surface nanostructures is highly important for various applications, and in particular for superhydrophobic properties. Here, taking 3,4-propylenedioxythiophene (ProDOT) as a model molecule, we study the influence of the decrease in the perfluorocarbon chain length or the use of two shorter perfluorocarbon chains on the formation of surface nanostructures and superhydrophobicity by electropolymerization. Moreover, perfluorinated compounds, especially those with long perfluorocarbon chains, are used a lot in industry but their persistence, bioaccumulation potential and toxicity alternatives are yet to be discovered. It seems that their effect is dependent on the perfluorinated chain length and that alternatives with shorter perfluorinated chains can be envisaged. Here, we show in the fabrication of superhydrophobic surfaces that the use of shorter perfluorocarbon chains can even, in certain conditions, lead to better properties. Superhydrophobic properties with extremely low hysteresis are obtained with long perfluorocarbon chains (C₈F₁₇) but very close properties are also obtained with short perfluorobutyl (C₄F₉) and even perfluoroethyl (C₂F₅) chains. Superoleophilic properties are obtained with C₂F₅ chains, whereas the best oleophobic properties were found with C₄F₉ chains. This is due to a change in the surface morphology from cauliflower structures to nanofibers as the perfluorocarbon chain decreases. By contrast, the use of two shorter perfluorocarbon chains induces very high steric hindrance during the electropolymerization and as a consequence smoother surfaces with lower surface hydrophobicity. Hence, it is possible to form structured or smooth surfaces using one or two fluorinated chains, respectively.