SURFACE CHARACTERIZATION OF OXYFLUORINATED ISOTACTIC POLYPROPYLENE FILMS - SCANNING FORCE MICROSCOPY WITH CHEMICALLY-MODIFIED PROBES AND CONTACT-ANGLE MEASUREMENTS

The surface of isotactic polypropylene (IPP) films modified by oxyfluo rination was studied by a combination of complementary techniques to e lucidate the effect of the modification on the chemical composition, s urface energy, and morphology. The elemental composition was measured by X-ray photoelectron spectroscopy (XPS), and the surface free energy was characterized by contact angle measurements with different liquid s. Following the approach by Good and co-workers, the acid-base charac teristics of the modified polymer surfaces were estimated. Subsequentl y, the modified IPP films were investigated by scanning force microsco py (SFM). In tapping mode SFM, the sample topography was imaged and th e surface roughness was quantitatively determined. Gold-covered SFM pr obes modified with carboxylic acid and methyl terminated self-assemble d monolayers of thiols were used to determine the pull-off force distr ibutions in ethanol. The interaction of the treated polymer film surfa ces with chemically functionalized SFM tips was shown to correlate wit h the surface tensions obtained by contact angle measurements. In part icular, pull-off forces measured with carboxylic acid functionalized t ips in ethanol depended approximately linearly on the basic part of th e surface free energy of the polymer film surface.