Plasma Technology for Deposition and Surface Modification (Science-Report Aus Dem Faserinstitut Bremen)

Plasma processing is a high-technology discipline in tailoring surface properties and in obtaining functional polymers of advanced materials without changing the material's bulk. Comparing with solid polymeric materials, special care should be taken for surface activation of textiles due to their complex geometries. It was found that modification is strongly influenced by both plasma parameters and fabric structure. As compared to air, CO2, and water vapor, Ar/O2 and He/O2 mixtures were found to be very effective for surface hydrophilization of polyester textiles due to the long-lasting free radical lifetimes. The modified surfaces were not stable for a long time due to restructuring of the polar functional groups. Therefore, plasma coatings containing functional groups are required in order to obtain a permanent surface modification. Permanent nanoporous coatings were deposited in order to obtain functional surfaces which contain accessible functionalities within the entire coating volume. This novel approach is essentially based on a fine control of simultaneous deposition and etching processes during plasma co-polymerization of ammonia with hydrocarbons. A nanoporous structure with a large specific surface area was achieved that contained functional groups inside the coating volume, which were accessible to e.g. dye molecules, thus facilitating substrate independent dyeing. A permanent hydrophilic modification of material surfaces was obtained by introducing nitrogen polar functionalities, depending on the NH3 to hydrocarbon ratio, which is mostly due to a replacement of carbon in a-C: H: N films. This novel combination of polar groups with a suitable texturing realized within crosslinked aC: H: N coatings proved to be an efficient method providing a long-term mechanical stability of superhydrophilic coatings. Moreover, plasma coated material surfaces contain huge numbers of functional groups which can chemically interact with matrix materials and hence, yield strong covalent bond between fiber and matrix. The coatings show a large surface area which enhances the contact area and surface texturing and additionally promotes mechanical interlocking. Thus, the novel, developed nanoporous coatings represent a platform for diverse multifunctional applications in the surface enhancement of advanced materials.