Low pressure plasma immobilization of thin hydrogel films on polymer surfaces

Thin films of poly(ethylene imine), poly(N-vinyl pyrrolidone) and poly(acrylic acid) were immobilized on poly(tetrafluoroethylene) and poly(ethylene terephthalate) surfaces using low pressure argon plasma. This technique allows to immobilize polymer films with a thickness of approximately 10 nm on polymeric substrates while functional groups and the mobility and swelling of the polymer chains are largely preserved. It is demonstrated, that through the suggested method coatings of very different hydrogel polymers can be obtained on very different polymeric substrates. Layer formation, plasma-induced anchorage and pH-dependent swelling of the immobilized hydrogels were analyzed by ellipsometry. X-Ray photoelectron spectroscopy was used to study the degree of degradation of the attached polymers caused by the plasma treatment. The pH-dependent ionization of the hydrogel layers in aqueous solutions was further characterized by streaming potential measurements.