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Vacuum-ultraviolet Photochemically Initiated Modification of Polystyrene Surfaces: Chemical Changes

Authors

  • Juan López-Gejo,

    1. Lehrstuhl für Umweltmesstechnik, Universität Karlsruhe, 76128 Karlsruhe, Germany
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  • Hartmut Gliemann,

    1. Institut für Nanotechnologie (INT), Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
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  • Thomas Schimmel,

    1. Institut für Nanotechnologie (INT), Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
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  • André M. Braun

    Corresponding author
    1. Lehrstuhl für Umweltmesstechnik, Universität Karlsruhe, 76128 Karlsruhe, Germany
      *To whom correspondence should be addressed: Lehrstuhl für Umwelt-messtechnik, Universität Karlsruhe, 76128 Karlsruhe, Germany. Fax: 00 49–721-608-6240; e-mail: andre.braun@ciw.uni-Karlsruhe.de
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  • Posted on the website on 2 February 2005

  • Presented as a poster at the VIII ELAFOT, La Plata, Argentina, 8–12 November 2004

*To whom correspondence should be addressed: Lehrstuhl für Umwelt-messtechnik, Universität Karlsruhe, 76128 Karlsruhe, Germany. Fax: 00 49–721-608-6240; e-mail: andre.braun@ciw.uni-Karlsruhe.de

ABSTRACT

Fourier-Transform infrared (FTIR) spectroscopy and surface energy analysis (contact angle measurements) have been performed as a means of identification and quantification of the functionalization of polystyrene surfaces upon vacuum ultraviolet- (VUV-) photochemically initiated oxidation. Photochemical oxidation was performed in the presence of water vapor and molecular oxygen using a pulsed Xe2-excimer radiation source (λexc: 172 nm). Surface oxidation was studied as a function of two parameters: irradiation time and distance between sample and radiation source. During the first 1–2 min of irradiation, an increase of the concentrations of hydroxyl (OH) and carbonyl (C=O) groups on the surface was observed, both reaching limiting values. As expected, the rate of oxidation diminished exponentially with increasing distance between the radiation source and the surface of the polystyrene film. Changes in the surface energy due to the introduction of these polar (i.e. OH and C=O) groups were also determined. The densities of the functional groups decreased upon washing with acetonitrile, and analysis of the washing solution by means of gas chromatography-mass spectrometry (GC-MS) revealed the presence of a large number of products. The application of pulsed Xe2-excimer radiation sources as a valuable alternative to conventional means (i.e. laser and plasma) for the photochemical oxidation and surface modification of polystyrene is discussed.

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