Photochemical functionalization of polymer surfaces for subsequent metallization

Abstract

Plasma-treated polymers typically show changes of surface morphology as well as modifications in their chemical composition. Both effects are known to have an influence on deposition and adhesion of metal coatings, although the exact mechanisms are not yet understood. Besides high-energy electrons and chemically active species, the generated UV radiation is one major component of plasma surface modification. The energy of ultraviolet photons is sufficiently high to induce bond scissions in polymeric materials, which result in subsequent chemical reactions.In this study, excimer radiation from lasers (e.g. KrF, 248 nm) or lamps (e.g. KrCl, 222 nm) was used for the formation of polar functional groups on the surface. The treatment was carried out at atmospheric pressure, mostly in air. The chemical and physical properties of the irradiated surface are different compared with untreated areas.The resulting functional groups allow for a spontaneous deposition of molecular thin films from aqueous solutions. In particular, these can be complexes from noble metals. Noble metals catalyze deposition in electroless metallization baths. A process for selective metal deposition on polymers has been developed based on this principle.After deposition, the main issue is the adhesion that can be achieved in the polymer–metal interface. It is determined by chemical or physical interaction between the polymer surface and the adjacent layer, as well as by typographical features.