Tuning Adhesion by Surface Modification with Mixed Polymer Brushes

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Adhesion at polymer-solid interfaces is of great importance for numerous applications from microelectronics to aircraft industry. It is essential, for permanent as well as for reversible adhesion, that the substrate's chemical composition and morphology is perfectly controlled. The project aims at the development of a new generation of adaptative surfaces based on chemically heterogeneous switchable thin polymer films, which covalently bond to a solid substrate, modifying therefore its surface chemistry in a well-controlled and reproducible way. Such films were recently fabricated from two incompatible polymer materials tethered at one end to the substrate (mixed polymer brushes). Those mixed brushes undergo phase segregation depending on environment resulting in a remarkable switching of morphology and surface energetic state. The project aims to study the influence of the switching phenomenon of mixed brushes on the strength of the interface which such a surface can form with an adhesive. These surfaces will be particularly useful to tune the adhesive properties of soft adhesives. This class of adhesives is gaining increasing interest in industry and medicine for its low toxicity and ease of use. Knowing the main requirements for such adhesives provides the capability to generate reversible, fast and easy adhering bonds to different substrates. We plan to prepare polymer films with adapting and switchable adhesive properties in a controlled environment. The mixed brush-like layers will be fabricated with "grafting to" and "grafting from" methods. Functional thin films for adapting and switchable adhesion will be quantitatively characterized with ellipsometry, XPS, XPEEM, FTIR/ATR, contact angle and AFM measurements. The consequences of this surface modification on adhesive and frictional properties will be investigated by a nano fracture test utilizing AFM and a probe test for elastomeric adhesives. The German group provides expertise in the area of film preparation, surface chemistry and surface characterization and the French group contributes expertise in the area of mechanical measurements and characterization of adhesive properties.