Modification, degradation, and stability of polymeric surfaces treated with reactive plasmas

The degradation, modification, and stability of polymeric surfaces exposed to chemically reactive O-2 and H2O-vapor plasmas were investigated. Specifi cally, the effects of these plasmas on etching rate, surface morphology, we tting instability, and fluid-holding capability were studied. Wetting insta bility is reflected by hydrophobic recovery and can be examined by the Wilh elmy balance method. Although hydrophobic recovery is usually attributed to surface configuration change, there are actually two types: reversible and permanent. Reversible hydrophobic recovery is caused by surface configurat ion change, whereas permanent hydrophobic recovery is caused by the creatio n of oxidized surface oligomers. This study distinguishes the two by identi fying differences in the shapes of the corresponding Wilhelmy force loops a nd in the fluid-holding parameter. The presence of surface oligomers was mo st detrimental to wetting stability and fluid-holding capability but could be controlled via the type of reactive gas, the discharge conditions, and t he polymer substrate. In general, polymers most susceptible to O-2-plasma e tching had the least surface oligomers and vice versa, whereas H2O-vapor pl asma suppressed surface oligomers on polymers less susceptible to etching. (C) 2000 John Wiley & Sons, Inc.