Ultrahydrophobic polymeric surfaces prepared using plasma chemistry

Ultrahydrophobic polymeric surfaces were prepared using two plasma chemistry approaches: (1) fluorocarbon plasma polymerization, and (2) simultaneous argon plasma etching of polypropylene (PP) surfaces and sputtering of poly(tetrafluoroethylene) (PTFE) onto these rough surfaces. In the first case, several fluorinated monomers were selected to study the effect of the monomer structure on the plasma polymer morphology and wettability. Ultrahydrophobic surfaces were generated for those monomer gases that were capable of forming powders. For fluoromonomers that did not form powders, the wetting characteristics were similar to that of PTFE. Plasma polymerization of perfluorohexane does not lead to powder deposition and the highest advancing water contact angle measured was 118° (the receding contact angle was 74°). Fluorinated acrylates and ethyl heptafluorobutyrate were tested as well and in all cases, the powder formation of the polymer led to highly hydrophobic surfaces (advancing and receding contact angles between 164°–174° and 8°–173°, respectively). In the second technique, argon plasma was used to etch PP surfaces, creating a rough surface (the roughness is controlled by the reaction time). Simultaneously, PTFE was sputtered onto the roughened PP surface to create fluorinated surfaces. The most hydrophobic surface exhibited an advancing contact angle of 172° and a receding contact angle of 169°. AFM and SEM analyses of these samples show that the powder deposition of the polymers and the etching of PP concurrent with the sputtering of PTFE lead to rough surfaces resulting in a highly nonwettable surface.