Surface chemical studies of aging and solvent extraction effects on plasma-treated polystyrene

A study of radio-frequency glow discharge (RFGD) plasma-modified polystyrene was performed using electron spectroscopy for chemical analysis (ESCA), contact angle measurements, and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Polystyrene was modified for varying lengths of time in air and water plasmas. The permanence of these treatments was evaluated with respect to time (aging) and solvent extraction. The samples were stored under ambient conditions and monitored over time to determine changes in elemental composition and functional group distributions at the surface. A post-modification solvent cleaning study was also performed to evaluate whether low molecular weight products of the plasma are present on the surface. The results indicate that the modifications are permanent with time, but produce some solvent extractable species. The stability of modifications, despite the production of low molecular weight solvent extractable products, is attributed to the physical structure of the polystyrene, and contrasted with previously published results from polyethylene and poly(ethylene terephthalate).