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The Evaluation of Oxygen Interactions with Materials III space-flight experiment was developed to obtain benchmark atomic-oxygen reactivity data and was conducted during Space Transportation System Mission 46. We present an overview of the flight experiment and the results of the Lyndon B. Johnson Space Center polymer chemistry and mass-spectrometer-carousel experiments. Mass-spectrometric measurements of gaseous products formed by O-atom reaction with 13 C-labeled Kapton™ revealed CO, CO2, H 2 O, NO, and NCh. By operating the mass spectrometer to detect naturally occurring ionospheric species, we characterized the ambient ionosphere at various times during the flight experiment and detected the gaseous reaction products formed when ambient ions interacted with the 13 C Kapton carousel sector. Direct comparison of the results of on-orbit O-atom exposures with those conducted in ground-based laboratory systems, which provide known O-atom fluences and translational energies, demonstrated the strong translational-energy dependence of O-atom reactions with a variety of polymers. A line-of-centers reactive scattering model was shown to provide a reasonably accurate description of the translational-energy dependence of polymer reactions with O atoms at high atom kinetic energies, and a Beckerle-Ceyer model provided an accurate description of O-atom reactivity over a three-order-of-magnitude range in translational energy and a four-order-of-magnitude range in reaction efficiency. Postflight studies of the polymer samples by x-ray photoelectron spectroscopy and infrared spectroscopy demonstrate that O-atom attackis confined to the near-surface region of the sample, that is, within 50 to 100 A of the surface. Nomenclature E a = apparent activation energy Eb = energetic barrier to reaction E t = kinetic energy of atom-surface collision R e = reaction efficiency r y = polymer surface temperature A = total residual error in a least-squares regression fit

SynopsisThe importance of nonexclusion effects in the GPC behavior of several stationary phases was investigated with DMF, 0.01M LiBr, as the mobile phase. Various low MW solutes and narrow MWD polymers, encompassing a wide range of polarities, were studied. The elution of the polymers was examined in terms of "universal calibration" behavior. Styragel and silanized glass both exhibit affinity for apolar polymers in DMF; for the former substrate this effect shows a strong inverse dependence on MW. As a consequence, application of polystyrene calibration curves to GPC analysis of more polar polymers with these substrates leads to overestimations of MW parameters. These errors are not corrected when universal calibration procedures are used. Ideal exclusion chromatography is exhibited by a number of polymers on untreated porous glass substrates. However, polymers with strong hydrogen-bonding functionality appear to be susceptible to marked adsorption in this system.

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