The use of thermally activatable adhesion promoters for permanent and durable immobilization of non-reactive polymeric coatings

Abstract

The problem of ice formation and accumulation on surfaces negatively impacts many aspects of daily life. Current strategies focus on the development of icephobic coatings that aim to repel water droplets and reduce the adhesion of ice. To function properly, icephobic coatings often require complex synthesis steps to be immobilized on surfaces, and permanent bonding with a substrate after synthesis is often not feasible. As the adhesion strength of coatings constitutes an important property that determines the performance and durability of adhesive coating systems, we immobilized polymers on different types of substrates with the use of an adhesion promoter to assess their adhesion strength. For that, lap shear tests were used to assess the adhesive bond strength of bound samples, using cyclic olefin copolymers (COCs) or epoxy as adhesives. The use of an adhesion promoter layer, capable of forming covalent bonds with any neighboring C–C bond via nitrene insertion, can increase the adhesion between materials that do not possess inherent chemical affinity, therefore creating an appropriate coating platform for adhesives that would not bind otherwise. Thermal curing of the samples with adhesion promoters containing the reactive 4-azido-3,5-difluorophenoxy (DFPxA) moiety led to increased adhesion strength. Additionally in this work, we immobilized different commonly used polymeric materials as monolayers on an aluminum substrate with the use of an adhesion promoter layer containing the reactive DFPxA moiety. Dynamic contact angle (dCA) and x-ray photoelectron spectroscopy (XPS) were used to assess the successful bonding of the reactive moiety with a wide range of different polymeric materials, demonstrating its universal attachment to neighboring bonds. Moreover, we investigated the adhesion strength of ice on immobilized monolayers of the coated polymeric films, which would not bind otherwise, revealing a correlation between adhesion strength and surface wettability.