Ultrahydrophobic polypropylene surfaces were prepared by the simultaneous etching of polypropylene and etching/sputtering of poly(tetrafluoroethylene) (PTFE) using inductively coupled radio frequency argon plasma. The semicrystalline polypropylene surface is roughened due to the differential rates at which the crystalline and amorphous regimes ablate and is also fluorinated by the fluorocarbon plasma that results from the ablation/depolymerization of PTFE. The roughness of the polypropylene is controlled by the time of plasma etching. The presence of PTFE increases the rate of polypropylene roughening by reactive ion etching. The resulting roughened and fluorinated polypropylene surfaces were characterized by water contact angle, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and atomic force microscopy (AFM). Wettability was found to depend on the size scale and topology of the roughness. The most hydrophobic surfaces exhibited advancing and receding water contact angles of θA/θR =...

Ultrahydrophobic polymer surfaces prepared by simultaneous ablation of polypropylene and sputtering of poly(tetrafluoroethylene) using radio frequency plasma

Films of polytetrafluoroethylene (PTFE) were deposited by laser ablation using the fourth harmonic, at 266 nm, of a Nd‐YAG laser. The films are found to be stoichiometric with the correct optical properties. We suggest that UV absorption onsets the pyrolitic decomposition of PTFE leading to a monomer that subsequently repolymerizes onto a substrate.

Deposition of polytetrafluoroethylene films by laser ablation

studied the effect ofpressure of argon as working gas at a constant distance of5cm between PTFE target and a substrate. It was shownthat both the chemistry, and the roughness of the surfacechanged with the Ar pressure during sputtering. Theauthorsconsideredthesurfaceroughnesstobeimportantfor the targeted super-hydrophobic effect. However, theroughness did not increase gradually with the pressure,but increased by a sudden jump for the highest pressure70Pa used. This result was interpreted as indicatingthat the plasma polymer clusters (nano and microparticles)formedintheplasmavolumewereburiedinto the plasma polymer ﬁlm growing on the substrate.This happened under particular deposition conditions(ﬂow of argon, RF power, target-substrate distance) atAr pressure of about 70Pa and higher. Based onscanningelectron microscopy (SEM) micrographs, this seemed toconﬁrmthehypothesisthatﬂuorocarbonplasmapolymerparticlesoriginatingintheplasmavolume(dustyplasma)were eventually embedded into the ﬁlm growing onthe substrate.On the other hand, several research groups claimed thatclusters (actually PTFE crystals) grown from CF

T. Robertson

Papers

R.F. sputtering of plastics