The effects of functional group mobility on quantitative ESCA of plasma modified polymer surfaces

Abstract

~Wetting nitrogen plasma modified polyethylene with a permeable solvent rapidly reduces the surface concentration of amines originally incorporated with plasma exposure. The rate of decrease in surface amine concentration increases with increasing hydrogen bonding capabilities of the solvent. A slower decrease in the surface amine concentration occurs for dry, modified polymers not wet with a solvent. A model consistent with a solvent mediated dilution of surface groups into the interior of the polymer is proposed. Upon protonation with aqueous H3PO4 or H,SO,, subsurface amines readily migrate back to the surface; HCI and HNOJ do not produce this result. The rate of concentration of protonated amines into the ESCA sampling depth is dependent on the permeability of the aqueous acid and the solubility of the corresponding protonated ammonium salt in polyethylene. The mobility of surface functional groups seriously affects the use of chemical derivatization reagents for the ESCA of modified polymer surfaces and raises important questions concerning the significance of a polymer surface analysis. The reaction of surface amines with pentafluorobenzaldehyde is used to illustrate this point.

Environment-Induced Surface Structural Changes of a Polymer: An in Situ IR + Visible Sum-Frequency Spectroscopic Study

“…Our findings reveal the dynamic nature of the polymer surface which depends strongly on the environment. This is consistent with results obtained by other techniques 22,23 and points to the need to characterize a polymer surface in its working environment in order to properly describe its surface properties. This work shows that SFG spectroscopy being highly surface-specific is uniquely suited for such studies.…”

pH responsive surfaces with nanoscale topography

“…Spontaneous surface rearrangement of either the hydrophilic or the hydrophobic block to the surface depends on the environment of exposure and should be reversible, back and forth, when the external conditions drive or counteract the surface energy minimization 9. Previous studies evidenced a similar behavior in plasma modified polyethylene with reversible wettability by exposure either to 2‐propanol or upon protonation with sulfuric acid 31. To address the reversibility of the process, we investigated the response in terms of surface chemical composition to environmental changes by measuring both contact angles and the amount of oxygen at the surface (XPS) during successive annealing treatments either to water or to dry air.…”

Surface characterization of air plasma treated poly vinylidene fluoride and poly methyl methacrylate films

“…It is well known that treatment of polymer films in gaseous plasma incorporates hydrophilic functionality, for example, treatment in nitrogen plasma incorporates nitro and primary amino groups at the surface [41,42], treatment in oxygen plasma incorporates hydroxyl, carbonyl, carboxylic acid functional group [43]. Air plasma treatment gives the combined effect of oxygen and nitrogen plasma.…”