OXIDATION AND ABLATION OF POLYMERS BY VACUUM UV-RADIATION FROM LOW-PRESSURE PLASMAS

Low-pressure glow discharge plasmas are increasingly used as an effect ive method for the surface modification of polymers; they can also ser ve in the laboratory to simulate low Earth orbital environment (LEG). Although Vacuum-Ultraviolet (VUV, lambda < 200 nm) is an important com ponent of plasma environment, only few studies have focused on its eff ects so far. The emission from low-pressure microwave plasma in the VU V-UV regions was investigated in order to use this plasma as light sou rces for the study of the VUV/UV effects on various polymers (polyethy lene, polymethylmelhacrylate, etc.) or high molecular weight oligomers (hexatriacontane). We have employed a quartz crystal microbalance (QC M) in order to measure in situ the net mass change of the polymeric fi lms exposed to VUV/UV radiation originating from hydrogen plasmas. Mea surements were made with the specimens in vacuum, or immersed in low-p ressure oxygen, directly exposed to the VUV/UV (perpendicular to the r adiation flux), or only to the VUV-generated atomic oxygen, AO (parall el to the radiation flux). Following irradiation, samples were analyse d by X-ray Photoelectron Spectroscopy (XPS), in order to study the evo lution of the oxygen content and of the various functional groups.