Ex-situ SIMS characterization of plasma-deposited polystyrene near atmospheric pressure
(2019) Applied Surface Science — Vol. 481, p. 1490-1502 (2019)
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- Authors
Cristaudo, Vanina 
- Abstract
- Polystyrene-like coatings are synthesized by plasma near atmospheric pressure. Elucidating their chemical structure after exposure to ambient air could be very challenging because of the interference of surface-related phenomena, mainly post-polymerization oxidation and contamination. In this paper, we propose secondary ion mass spectrometry (SIMS) in molecular depth-profiling mode, combined to multivariate analysis, as a more reliable tool for their investigation as a function of the injected power. Indeed, the information provided by the inner layers is more representative of the film in growth. The SIMS approach is validated by complementary, surface-sensitive and bulk techniques: X-rays photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). The SIMS results suggest that the high concentration of -CH3 groups in the polymer matrix, pointed out by IR, is due to branching and/or grafting of CH3· radicals to active sites (prevalently in position α, β, γ) along the aliphatic backbone, in addition to a significant fraction of trapped oligomers. The oligomer contribution is supported by an original study based on the molecular weight dependence of the sputtering efficiency. The overall experimental evidences indicate a milder fragmentation of the precursor at lower powers, leading to a higher conservation of the aromaticity and a lesser branched and/or cross-linked content.
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Citations
Cristaudo, V., Merche, D., Poleunis, C., Devaux, J., Eloy, P., Reniers, F., & Delcorte, A. (2019). Ex-situ SIMS characterization of plasma-deposited polystyrene near atmospheric pressure. Applied Surface Science, 481, 1490-1502. https://doi.org/10.1016/j.apsusc.2019.03.032 (Original work published 2019)