AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA6
Gas-Phase Diagnostics and Mechanisms of Energy Transfer in O@sub 2@/NH@sub 3@ Plasmas

Thursday, November 6, 2003, 3:40 pm, Room 315

Session: Plasma Diagnostics: Mechanisms
Presenter: K.R. Kull, Colorado State University
Authors: K.R. Kull, Colorado State University
D.S. Wavhal, Colorado State University
E.R. Fisher, Colorado State University
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Hydrophobic polymeric membranes are used extensively throughout a variety of industrial and biomedical processes. To improve the separation performance, hydrophilic surface modification is required. In this work, we have studied hydrophilic modification of asymmetric porous polyethersulfone membranes using N@sub 2@, NH@sub 3@ and O@sub 2@/NH@sub 3@ plasma treatments. Membrane treatments using 100% N@sub 2@ or 100% NH@sub 3@ plasmas yielded incomplete hydrophilic treatments. In contrast, the O@sub 2@/NH@sub 3@ plasma treatment produced a hydrophilic membrane that retained its hydrophilicity over an extended period after treatment. Examination of the plasma gas-phase composition using optical emission spectroscopy and mass spectrometry revealed the NH radical is present in both the 100% NH@sub 3@ and the O@sub 2@/NH@sub 3@ systems, whereas the OH radical is only observed in the O@sub 2@/NH@sub 3@ plasma. Evidence from other plasma modification systems indicates the OH radical is critical for permanent hydrophilicity using non-polymerizing plasma treatments of polymeric membrane treatments.@footnote 1@ To better understand the chemistry that occurs during these processes, we have used our laser-induced fluorescence based imaging technique to characterize the relative densities of NH and OH and their energy partitioning in these plasmas. The relative densities of both radicals are dependent on the applied rf power (P) and feed gas composition dependent. Interestingly, the rotational temperatures of both species appear nearly independent of P. Surface interactions of NH and OH with membranes, as well as their translational temperatures in the plasma, will be presented and compared to earlier results for NH@sub 2@ radicals in NH@sub 3@ plasma.@footnote 2@ Implications for plasma modification mechanisms will also be discussed. @FootnoteText@@footnote 1@ M. L. Steen, et al., Langmuir 17, 2001, 8156.@footnote 2@ C. I. Butoi, et al.,J. Phys. Chem. B 105, 2001, 5957.