Plasma modification of polymethylmethacrylate and polyethyleneterephthalate surfaces

Abstract

Noble gas (He,Ar,Xe) and reactive gas (O2,N2) plasma treatments of polymethylmethacrylate (PMMA) and polyethyleneterephthalate (PET) surfaces were performed in an electron-cyclotron-resonance plasma. In situ surface analysis by x-ray photoelectron spectroscopy reveals well-defined surface compositions. From these measurements it is concluded that, independently of the plasma gas, the plasma ions easily decompose the ester group in PMMA in its constituents by an ion-electron recombination process, while in PET the ester decomposition is less pronounced. The difference is ascribed to the presence in PET of a phenyl ring, which protects the ester group by various mechanisms. The study of O2 plasma treatments shows that the equilibrium between the depletion of oxygen and the incorporation of the reactive species in the polymer surface is solely determined by the ion current. The plasma-polymer interactions are qualitatively explained by simple rules of intermolecular forces and ion-electron recombination phenomena.