THE ROLE OF PLASMA ION IN PMMA AND PET SURFACE MODIFICATION DURING ECR PLASMA TREATMENT

Noble gas and reactive gas (O-2, N-2) plasma treatments of polymethylm ethacrylate (PMMA) and polyethyleneterephthalate (PET) surfaces were p erformed in an electron cyclotron resonance (ECR) plasma. In situ surf ace analysis by X-ray photoelectron spectroscopy (XPS) reveals well-de fined surface compositions. We observed that, independently of the pla sma gas, the plasma ions decompose the polar ester group on the polyme r surfaces in its constituents by an ion-electron recombination proces s. The process was much stronger for PMMA than for PET. We ascribe the difference to the presence in PET of a phenyl ring, which protects th e ester group by various mechanisms. The role of the plasma ions was p roved with ion gun treatments. The results demonstrate the crucial imp ortance of the ions for the surface modification of polymers during pl asma treatment.