A SPECTROSCOPIC ANALYSIS OF PLASMA POLYMERS PREPARED FROM A SERIES OF VINYL SULFONES

Plasma polymers (PPs) have been prepared from methyl vinyl sulphone (MVS), ethyl vinyl sulphone (EVS) and vinyl sulphone (VS). The ratio of radio frequency (r.f.) power (W) to flow rate of monomer (F) or W/F is an important parameter in plasma polymerization. PPs prepared at low and high W/F were analysed by x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and grazing angle infra-red (GAIR) spectroscopy. XPS revealed that significant quantities of the sulphone group had been retained from the monomer. The greatest retention was observed in the PPs that had been prepared at low W/F, where the majority of the sulphur was present as RSO2R/H. The remaining sulphur being in RSOR/H and RSR/H environments. This trend was reversed in the PPs prepared at high W/F. The negative secondary ion mass (SIM) spectra of PPs prepared at high and low W/F were examined and structures proposed for the prominent ions. The relative intensities of these ions were different for the PPs prepared at high and low W/F. This showed that there had been a greater retention of structures from the monomer in the PPs that were prepared at low W/F. The GAIR spectroscopy confirms the presence of sulphone groups throughout the PP film. It also shows that carbonyl groups are present which cannot be confirmed by XPS alone.