Influence of long alkyl spacers in the elaboration of superoleophobic surfaces with short fluorinated chains
Résumé
In order to produce extremely high oleophobic properties with a low fluorine content, long dodecyl spacers were introduced between a polymer and fluorinated chains in order to reduce the mobility of the fluorinated chains, especially short perfluorobutyl (F-butyl) chains. We report the synthesis and characterization of electrodeposited polymer surfaces obtained from original fluorinated 3,4-ethylenedioxypyrrole (EDOP) derivatives. Semi-fluorinated chains of three different lengths (F-octyl: PEDOPC12F8, F-hexyl: PEDOPC12F6 and F-butyl: PEDOPC12F4) were grafted to EDOP and separated with a n-dodecyl chain in order to reduce the mobility of F-butyl chains. For the first time, a surprisingly high contact angle of 138u was measured with hexadecane on PEDOPC12F4, although F-octyl tails are necessary to produce robust superoleophobic surfaces. By producing smooth surfaces, we successfully separate the influence of the intrinsic hydro- and oleophobicity and the surface structuration on the static contact angles of water and hexadecane. Here, the surface structuration increases the contact angle of hexadecane by 90u for PEDOPC12F4. The Cassie-Baxter equation predicts a porosity of 84.5% between the surface and a hexadecane droplet.