To perform a systematic study over a broad parameter range of acrylic acid discharges, we varied the energy input W/F over a wide range. Five different regimes could be identified (from low to high energy input): regime I, where oligomerization takes place; regime II, the radical‐dominated plasma polymerization of acrylic acid; regime III, a transition regime showing etching/oxidation effects; regime IV, where the plasma polymerization resembles the one observed for CO2/C2H4 discharges; and regime V, where etching effects yield a reduction in deposition rate. These results show that the polymerization mechanism can be described as a function of the energy input W/F. Specifically, a parameter range where acrylic acid can be replaced by CO2/C2H4 discharges has been identified.magnified image

Holding its breath: Small Pd particles on an Fe3O4 support reversibly store large quantities of oxygen in the form of a thin Pd oxide layer at the particle/support interface. Oxygen from this reservoir can be released during oxidation reactions, as shown by a combination of molecular beam methods, scanning tunneling microscopy, and photoelectron spectroscopy.

ABSTRACT:The surface degradation and production of low molecular weight oxidized materials (LMWOM) on biaxially oriented polypropylene (BOPP) and low-density polyethylene (LDPE) films was investigated and compared for two different dielectric barrier discharge (DBD) treatment types, namely air corona and nitrogen atmospheric pressure glow discharge (N 2 APGD). Contact angle measurements, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) analyses were performed in conjunction with rinsing the treated films in water. It is shown that N 2 APGD treatments of both polyolefins result in much less surface degradation, therefore, allowing for a significantly higher degree of functionalization and better wettability. Hydrophobic recovery of the treated films has also been studied by monitoring their surface energy (␥ s ) over a period of time extending up to several months after treatment. Following both surface modification techniques, the treated polyolefin films were both found to undergo hydrophobic recovery; however, for N 2 APGD modified surfaces, ␥ s ceases to decrease after a few days and attains a higher stable value than in the case of air corona treated films.

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Functional plasma polymers were deposited from pure ethylene discharges and with the addition of carbon dioxide or ammonia. The incorporation of oxygen and nitrogen-containing functional groups depends on the fragmentation in the gas phase as well as on the densification during film growth. While a minimum energy per deposited carbon atom is required for cross-linking, the densification and accompanying reduction of functional group incorporation was found to scale linearly with momentum transfer through ion bombardment during film growth.