Laser-induced surface modification of polystyrene

The modification induced in polystyrene (PS) by the ArF excimer laser radiation has been investigated. Various numbers of the laser pulses of the energies below the material ablation threshold were applied. Changes in the chemical composition of the PS surface layer were studied by the X-ray photoelectron spectroscopy (XPS). Analysis of the morphological changes in the polymer surface layer was performed via the atomic force microscopy (AFM). The contact angles of test liquids (water and diiodomethane) were measured with use of a goniometer while the surface energy (SE) was calculated by the Owens-Wendt method. It was found that the surface energy change was mainly affected by surface roughness caused by the laser radiation and that surface oxidation had not considerably contributed to this change. The increase in the SE was mostly due to its disperse component.