The polymer surface compositions of some polyesters of importance in biomaterial science and advanced drug delivery have been examined by x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS). The XPS results show good quantitative stoichiometric correlation with the known chemical composition of the polyesters. The SIMS spectra show systematic fragmentation patterns in both positive and negative ion modes for the series of structurally related polymers. Evidence for the presence of radical cation formation in SIMS is presented. Comparison between the SIMS spectra of poly-glycolic acid and ply-lactic acid and the pyrolysis mass spectra of these polymers are made, and conclusions drawn on the different mechanisms of fragmentation. The combined application of SSIMS and XPS is shown to give a highly detailed analysis of these polyesters.

Polytetrafluoroethylene sheet samples have been treated in a low-power plasma cell using O 2 , Ar, N 2 and NH 3 feed gases. The surfaces became significantly more wettable in simulated body fluid and bromonaphthalene. By using a range of techniques, this was found to be principally due to chemical changes at the surface induced by the plasma treatments. Static SIMS and XPS showed that these changes were defluorination and incorporation of unsaturated hydrocarbons and oxygen-containing moieties. The extent of these changes depended on the feed gas used, being least for O 2 and greatest for Ar. In addition, it was found that surfaces became activated by the plasma treatments and continued to change chemically during subsequent storage in simulated body fluid. By contrast, storage in air resulted in partial recovery towards the untreated surface state, which was attributed to relaxation processes in the modified layer.

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Following the recent observation in this laboratory of a charge induced damage effect in insulators under inert gas ion bombardment, the influence of the charge state of the beam (ion or atom) on the sputtering yield of insulating and semiconducting materials has been investigated. A series of sputter measurements has been carried out on Au, Ta2O5, Si, GaAs, and glass using calibrated ion and atom fluxes. For this purpose a recently developed gun capable of producing raster-scanned, microfocused energetic ion or atom beams was employed. While for the conductor Au, as expected, no effect was seen, for the remaining materials sputter yield increases of up to 150% were observed under ion bombardment which implies the existence of a substantial electronic sputtering effect in insulators and semiconductors due to low-energy ion bombardment.