A comparison of plasma-oxidized and photo-oxidized polystyrene surfaces

High-resolution core-level and valence-band X-ray photoelectron spectroscopic measurements show that polystyrene surfaces become more heavily oxidized during ultraviolet photo-oxidation than under plasma oxidation. A greater proportion of- C O 2-linkages are evident following the former treatment, along with the virtual absence of any phenyl features in the valence region and an attenuated π-π∗ shake-up satellite in the C(1s) spectra. This apparent paradox of the more reactive medium producing a less oxidized surface is explained in terms of the complex plasma-surface interactions associated with the exposure of a polymer surface to an oxygen glow discharge.