XPS [X-ray photoelectron spectroscopy] studies of plasma-modified polymer surfaces

Plasma (glow discharge) treatment is typically used to modify the surface of a polymer to improve adhesion, wettability, or to prevent degradation of a polymer surface during metallization. Such low-power plasma treatments affect only the outer tens of angstroms of a polymer surface making it difficult to elucidate the chemistry of these modified surfaces. X-ray photoelectron spectroscopy (XPS) is an ideal technique to characterize plasma-modified polymer surfaces due to its inherent surface sensitivity. XPS was used to study the chemical effects of both inert (argon) and reactive (oxygen and nitrogen) gas plasma treatments done in-situ on a variety of polymer surfaces. In general, inert gas plasma treatments introduce no new detectable chemical species onto the polymer surface but can induce degradation and rearrangement of the polymer surface. However, plasma treatments with reactive gases such as oxygen and nitrogen create new chemical species which dramatically alter the chemical reactivity of the polymer surface. XPS studies have also shown that the surface population of chemical species formed after plasma treatment is strongly dependent on the chemical structure of the polymer