Selective surface functionalization of polystyrene by inner-shell monochromatic irradiation and oxygen exposure

The surfaces of polystyrene (PS) thin films were selectively functionalized by a combination of monochromatic synchrotron radiation with oxygen exposure. By selecting specific K-shell excitation energies, it was shown that highly efficient surface functionalization can be obtained. After the treatments, several oxygen functionalities were detected by XPS and NEXAFS spectroscopy. The functionalization strongly depended on the excitation energy. C 1s → σ*C–C transitions produced an extremely efficient oxidation of the uppermost monolayer of the PS films. The COO and CO elemental contributions in the C 1s envelope at the PS surface was higher than 70%. On the contrary, other excitation energies did not introduce COO functionalities efficiently. The obtained results were explained by taking into account the known Auger stimulated desorption mechanism. The present research will open new ways to functionalize a polymer surface by a combination of monochromatic inner-shell excitation together with exposure to a reactive gas atmosphere.