SECONDARY-ION MASS-SPECTROMETRY TIME-OF-FLIGHT AND IN-SITU X-RAY PHOTOELECTRON-SPECTROSCOPY STUDIES OF POLYMER SURFACE MODIFICATIONS BY A REMOTE OXYGEN PLASMA TREATMENT

Surface modifications induced by a remote oxygen microwave plasma on t hree different polymers (LDPE, PS, PMMA) have been extensively investi gated in situ by x-ray photoelectron spectroscopy (XPS) and, after tra nsfer in atmosphere, by time of flight secondary ion mass spectrometry (TOF SIMS). By a direct transfer from the plasma chamber to the XPS s pectrometer the chemical functionalities introduced on the surface of the polymeric substrate are identified and quantitatively determined. Furthermore, high resolution molecular analysis by TOF SIMS allows a b etter understanding of the chemical changes induced by the oxygen plas ma. The information gathered from the two techniques permits us to pro pose oxidation mechanisms of the polymer surfaces. The relative densit y of ground state atomic oxygen O(P3) in the remote discharge is shown to be of fundamental importance for the initiation of the oxidation. This species is responsible for the formation of radicals from which a re further produced highly oxidized functionalities (O-C=O, O2C=O). Sp ecific sites of oxidation for the three polymers and a depolymerizatio n mechanism for PMMA are evidenced by TOF SIMS analysis.