AVS 49th International Symposium
    Plasma Science Friday Sessions
       Session PS-FrM

Paper PS-FrM4
Hydrophilic Plasma Surface Modification of Membranes: Surface Analysis, Gas-Phase Diagnostics, and Mechanisms of Energy Transfer

Friday, November 8, 2002, 9:20 am, Room C-103

Session: Plasma Surface Interactions II
Presenter: K.R. Kull, Colorado State University
Authors: K.R. Kull, Colorado State University
J. Zhang, Colorado State University
E.R. Fisher, Colorado State University
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Treatments with nitrogen containing plasma that render asymmetric polyethersulfone (PES) membranes permanently hydrophilic are reported. The modification strategy entails treating these membranes downstream from an inductively coupled rf plasma source. Contact angle measurements confirm that the membranes are wettable as a result of treatment with plasmas containing nitrogen species (Ar/NH@sub 3@, O@sub 2@/NH@sub 3@, N@sub 2@). More importantly, the hydrophilic modification is permanent as plasma-treated membranes remain wettable for more than eight months after plasma treatment. The change in wettability is a result of chemical changes in the membrane induced by plasma treatment. FTIR and XPS analysis of treated membranes reveals the incorporation of nitrogen functionalities into the treated membranes. Moreover, there is a concomitant increase in the oxygen to carbon ratio compared to the untreated PES membrane. Mass spectral data reveals gas-phase species are created from plasma-membrane interactions and SEM investigations reveal no visually observable structural damage as a result of the treatment parameters employed. We have also investigated the role of NH and NH@sub 2@ radicals in the modification process using laser-induced fluorescence measurements. The velocity of NH radicals in the nitrogen-containing plasmas has been measured and appears to be rf power dependent. Additional data on the surface interactions of NH with PES membranes as well as velocity measurements for scattered NH radicals will be presented and compared to earlier results for NH@sub 2@ radicals.@footnote 1@ Implications for plasma modification mechanisms will also be discussed. @FootnoteText@ @footnote 1@C. I. Butoi, M. L. Steen, J. R. D. Peers, E. R. Fisher, J. Phys. Chem. B 105, 2001, 5957.