• Pletincx, Sven
• Terryn, Herman
• Hauffman, Tom

Abstract

1. Introduction<br/>Polymer/(hydr)oxide/metal systems play an important role in engineering, more specifically in aerospace, microelectronics, transport and packaging industry. One of the main goals in interface engineering is the achievement of high adhesion strengths at polymer/metal interfaces and this even in aggressive conditions. At the interface of these two regions, interatomic and intermolecular interactions result in adhesion. Bonds at the interface of these hybrid systems determine the performance of the coatings or adhesives as they have to withstand high mechanical forces and corrosive attacks over long periods.[1] In order to investigate the interface region, one has to use an appropriate analysis technique and methodology that allows to access this region in order to probe and extract useful information. This is very challenging, mainly because of the relative thick (µm) polymer layer present in conventional systems resulting in a buried interface, which is difficult to characterize with several surface-sensitive analysis techniques, such as XPS and AES. In nowadays literature two main approaches exist to reach the interface region. The first approach is an indirect accessing approach where a polymer coating with thicknesses from ten to hundreds of microns is stripped off or is sputtered away to reach the interface. However, it is not known whether the interface of the stripped-off remnant represents the real interface or if the energetic sputtering process alters the interface.[2] In a second approach, monomeric compounds are adsorbed on a range of metal oxides. By using these thin depositions, the interface can be reached easily and is well understood. However, layers of these monomeric compounds do not have the same bulk properties as polymeric coatings as they do not consist of macromolecules. With this approach it is also unknown whether the interface is the same as for polymer systems.[3] Therefore in this work, a new approach will be used to access the buried interface. The coating will be tuned in such a way that it has the same bulk properties as the conventional polymer and it will be made sufficiently thin to access the interface by non-destructive techniques. <br/><br/>2. Experiments and discussion<br/>By focusing on the adsorption of nanometer thin polymer films on oxides, it is possible to characterize the interface region on a non-destructive way by several dedicated top surface (vacuum)- and optical techniques. The synthesis of nanometer thin polymer films is studied on well-tuned aluminum oxide layers.[4] Aluminum is one of the most used engineering metals and the use of polymer-coated aluminum is widespread. Because the oxide chemistry and composition of the aluminum have a direct influence on the bonding behavior with the functional groups of the polymer and therefore the tuned oxide-layer is characterized in this work. Polymers with a carboxyl functional group are used to adsorb on the aluminum oxide layer because it is known that these functional groups hydrolyze and form a carboxylate-metal oxide ionic bond.[5] After the characterization of this polymer-metal oxide bond by XPS, AES and FTIR, it is also important to understand its stability in an aqueous environment. A combination of in-situ techniques such as VISE, ATR-FTIR based on the Kretschmann geometry and EIS give insight in the diffusing and migrating behavior of water and other ionic components and their effect on the stability on the existing bonds.[6] Combining this knowledge will eventually allow the modification of the surface oxide and synthesis of polymers with specific functional groups to create a specific bond with the organic top layer in order to increase the durability of hybrid systems in humid or aggressive conditions.<br/><br/>3. References<br/>[1] G. Grundmeier and M. Stratmann, Annu. Rev. Mater. Res., vol. 35, no. 1, pp. 571–615, Aug. 2005.<br/>[2] A. J. Pertsin and Y. M. Pashunin, Appl. Surf. Sci., vol. 44, pp. 171–178, 1990.<br/>[3] P. Taheri, J. R. R. Flores, F. Hannour, J. H. W. H. W. de Wit, H. Terryn, and J. M. C. M. C. Mol, J. Phys. Chem. C, vol. 117, no. 7, pp. 3374–3382, Feb. 2013.<br/>[4] T. Hauffman, A. Hubin, and H. Terryn, Surf. Interface Anal., vol. 45, no. 10, pp. 1435–1440, 2013.<br/>[5] R. Tannenbaum, S. King, J. Lecy, M. Tirrell, and L. Potts, Langmuir, vol. 20, no. 18, pp. 4507–4514, 2004.<br/>[6] M. Öhman and D. Persson, Electrochim. Acta, vol. 52, no. 16, pp. 5159–5171, Apr. 2007. <br/><br/>

Topics

• Deposition
• surface
• compound
• polymer
• experiment
• x-ray photoelectron spectroscopy
• aluminum oxide
• aluminium
• strength
• electrochemical-induced impedance spectroscopy
• durability
• atomic emission spectroscopy
• Auger electron spectroscopy