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

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 theta(A)theta(R) = 172 degrees/169 degrees.