AN INVESTIGATION OF THE SURFACE-CHEMISTRY OF POLY(ETHER ETHERKETONE) .1. THE EFFECT OF OXYGEN PLASMA TREATMENT ON SURFACE-STRUCTURE

Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS) have been employed to study the plasma surface oxidation of poly(ether etherketone) (PEEK). The positive and negative ion ToF-SIM spectra obtained from a cleaned PEEK surface were easily interpreted using conventional mass spectrometry rules. Plasma oxidation of PEEK was found to produce complex positive and negative ion spectra. In these spectra, ions diagnostic of the PEEK repeat unit were much reduced in intensity, and new ions diagnostic of plasma treatment were introduced. However, a thorough interpretation of these spectra was not attempted. The corresponding XP C 1s and O 1s core-level spectra were run. In the C 1s core level, surface oxidation produces a number of new carbon-oxygen environments and an increase in the number of oxidized carbons. In both the C 1s and O 1s core levels, the increased full width at half-maximum (FWHM) required to fit these spectra is suggestive of several environments being contained within each of the peaks fitted. The plasma-treated polymer surface was rinsed with methanol. In the ToF-SIM spectra, rinsing removes or reduces the intensities of the ions introduced by plasma treatment and enhances the intensities of some ions not previously noted; but rinsing does not restore the original PEEK spectra. In the C 1s core-level spectrum, rinsing was found to reduce the number of oxidized carbons and, in particular, the concentration of the environments introduced by the environment introduced by plasma treatment. Further, it proved possible to fit the C 1s core level with a FWHM comparable to that employed for the clean PEEK: this may be indicative of a reduction in the variety of carbon-oxygen environments.