The surface properties of poly(dimethyl siloxane) (PDMS) layers screen printed onto silicon wafers were studied after oxygen and ammonia plasma treatments and subsequent grafting of poly(ethylene -alt-maleic anhydride) (PEMA) using X-ray photoelectron spectroscopy (XPS), roughness analysis, and contact angle and electrokinetic measurements. In the case of oxygen-plasma-treated PDMS, a hydrophilic, brittle, silica-like surface layer containing reactive silanol groups was obtained. These surfaces indicate a strong tendency for "hydrophobic recovery" due to the surface segregation of low-molecular-weight PDMS species. The ammonia plasma treatment of PDMS resulted in the generation of amino-functional surface groups and the formation of a weak boundary layer that could be washed off by polar liquids. To avoid the loss of the plasma modification effect and to achieve stabilization of the mechanically instable, functionalized PDMS top layer, PEMA was subsequently grafted directly or after using gamma-APS as a coupling agent on the plasma-activated PDMS surfaces. In this way, long-time stable surface functionalization of PDMS was obtained. The reactivity of the PEMA-coated PDMS surface caused by the availability of anhydride groups could be controlled by the number of amino functional surface groups of the PDMS surface necessary for the covalent binding of PEMA. The higher the number of amino functional surface groups available for the grafting-to procedure, the lower the hydrophilicity and hence the lower the reactivity of the PEMA-coated PDMS surface. Additionally, pull-off tests were applied to estimate the effect of surface modification on the adhesion between the silicone rubber and an epoxy resin.

Two modification routes have been applied to control the surface properties of spin-coated and screenprinted poly(dimethylsiloxane) (PDMS) layers and to improve their adhesion to a photopatternable epoxy resin topcoat. The first route is based on the optimization of low-pressure oxygen and ammonia plasma treatments to generate acidic or basic reactive surface groups capable of forming covalent bonds with the epoxy groups of the topcoat. The main disadvantage of these fast and practicable processes is the instability of the modification effects. Therefore, the plasma-activated PDMS surfaces were used for subsequent 'grafting to' procedures with reactive polymers. The functional surface groups generated by oxygen or ammonia plasma treatments of PDMS (SiOH, OH, COOH and NH 2 ) were used as anchors to graft epoxy group containing homopolymers and copolymers as well as maleic anhydride copolymers. All of grafted materials provided thin barrier layers that prevented the hydrophobic recovery of the modified PDMS surface. A very promising concept to tailor the surface properties of PDMS is the grafting of epoxy group containing methacrylate copolymers. Depending on the molar ratio of the monomers used the epoxy groups will act mainly as anchor groups. The surface properties of the grafted layer will, then, be controlled by the functionality of the second comonomer.In order to study the effect of the surface modifications on the surface properties of the silicone elastomer layers we used a combination of various surface-sensitive characterization techniques, namely, X-ray photoelectron spectroscopy (XPS), contact angle and electrokinetic measurements as well as roughness analysis. Additionally, pull-off tests were carried out to quantify the effect of the surface modification on the adhesion between an epoxy resin and PDMS.

In zahlreichen wirtschaftlich bedeutenden Technologiebereichen ist die Haftung von Verbundsystemen von zentraler Bedeutung. Das betrifft zum Beispiel die Lackierungen von Oberflächen und die Verbundherstellung. Besondere Probleme bereiten bei der Verbundbildung Polyolefine, Silikone und Fluorpolymere auf Grund ihrer sehr geringen Oberflächenenergie. Die Modifizierung solcher Polymeroberflächen mit dem Ziel einer chemischen Funktionalisierung und damit der Erhöhung der Oberflächenenergie kann zu einer Verbesserung der Adhäsionseigenschaften der Materialien führen. Ein gut eingeführtes Verfahren, vor allem in der Automobilindustrie, ist das Beflammen der Oberflächen. Jedoch ist eine definierte chemische Änderung der Oberfläche von sehr vielen Einflussparametern abhängig und somit sehr schwer zu standardisieren. Eine definierte Änderung der Oberfläche kann besser durch eine gezielte Plasmabehandlung erreicht werden, wobei hier die Oberfläche durch einen anschließenden nasschemischen Prozessschritt stabilisiert wurde.