Modification of Polymeric Surfaces With Plasmas

Abstract

As adaptable as polymeric materials are in their many applications to our daily lives, the need exists to tailor the polymer surfaces to provide even more flexibility in regard to their uses. Plasma treatments offer an unprecedented spectrum of possible surface modifications to enhance polymers, ranging from simple topographical changes to creation of surface chemistries and coatings that are radically different from the bulk polymer. Furthermore plasma treatments are environmentally friendly and economical in regard to their use of materials.Plasma processing can be classified into at least four categories that often overlap. These are the following: (1) surface preparation by breakdown of surface oils and loose contaminates, (2) etching of new topographies, (3) surface activation by creation or grafting of new functional groups or chemically reactive, excited metastable species on the surface, and (4) deposition of monolithic, adherent surface coatings by polymerization of monomeric species on the surface. Key features of these processes will be briefly discussed, with a rudimentary introduction to the chemistries involved, as well as examples. Focus is placed on capacitively coupled radio-frequency (rf) plasmas (see Figure 1 in the article by Lieberman et al. in this issue of MRS Bulletin) since they are most commonly used in polymer treatment.

Etching Processes of Polytetrafluoroethylene Surfaces Exposed to He and He–O2 Atmospheric Post-discharges

“…Contrary to treatments in pure helium, the addition of oxygen into the discharge implies wettability and roughness modifications generated by an anisotropic etching of PTFE surfaces. It is well-known that the addition of an oxidant gas (e.g., oxygen) usually leads to a hydrophilic surface as polar functional groups are introduced into the polymer surface. , In the case of PTFE, the behavior is more controversial as O 2 -containing plasmas can lead to more hydrophobic − or hydrophilic surfaces. , However, the PTFE treated samples showing an increase in hydrophobicity in the literature seem to have the same behavior regarding chemistry and morphology as our samples. No modification has been highlighted by XPS analyses, and an increase in roughness has been observed.…”

“…It is well-known that the addition of an oxidant gas (e.g., oxygen) usually leads to a hydrophilic surface as polar functional groups are introduced into the polymer surface. 59,60 In the case of PTFE, the behavior is more controversial as O 2containing plasmas can lead to more hydrophobic 6−10 or hydrophilic surfaces. 11,12 However, the PTFE treated samples showing an increase in hydrophobicity in the literature seem to have the same behavior regarding chemistry and morphology as our samples.…”

Overcoming mass‐transfer limitations in partial hydrogenation of soybean oil using metal‐decorated polymeric membranes

“…Gas selectivities after sputtering also change depending upon among other factors the initial α H2/N2 (representing the quality of the asymmetric polymer membrane), the extent of coverage of the membrane surface with metal, and the possible modification of the membrane polymer skin layer itself by the sputtering plasma 22,23 .…”

Wettability Interpretation of Oxygen Plasma Modified Poly(methyl methacrylate)

“…The effect of plasma surface modification mainly depends on the combination of the type of gas and chemical structure of the polymer. ,, Among various plasma treatments, oxidative (oxygen and air) plasma treatment was found to be an effective tool for improving wettability. It is well-known that when a polymer is treated with O 2 plasma, polar functional groups containing oxygen are introduced into its surface, leading to a hydrophilic surface. , However, most work has neglected the influence of surface charges on the change in wettability; relatively fewer studies claimed the relationship between the surface charge and the wettability of the modified surfaces . So far, the cause of the wettability difference during plasma treatment is not completely understood; the structural state and chemical modification of a surface and its wettability can be complex, and much effort is being directed toward understanding the wetting process …”