FWO-SB-Beurs: Probing of formation and degradation of the chemical interface between metal (oxides) and organic coatings (FWOSB19)

(i) Problem definition and objectives Hybrid polymer/(hydr)oxide/metal systems such as adhesive bonding and organic coatings are established industrial technologies. However, these important technologies suffer of several technological problems of strategic importance. The most important problems include the loss of adhesion strength in the presence of humidity and ionic compounds together with the need for high temperatures in order to cure a thermoset adhesive/coating or to anneal the polymer. The durability of the entire system is largely determined by the interface between the organic layer and the metal oxide. Notwithstanding this region is important in understanding de-adhesion of the polymer layer, it is fair to say that not much is understood of this region. The investigation of the binding and degradation mechanisms occurring at the interface region is not an easy task as this region is masked by a µm-thick polymer layer. Therefore, this region is often called the buried interface. Current state-of-the-art methodologies risk to modify this region or use a destructive way of analysing the interface. Therefore, it is the aim of this PhD project to unravel the interface of hybrid organic/metal oxide systems while simultaneously probe the effect of moisture, ions of an electrolyte and temperature changes. (ii) Methodology and used technology The methodology used focusses on chemical bonding theory by representing the real case system using a polymer-on-metal approach while avoiding modifications to the interface region. The nature and character of the metal oxide surface is very important in establishing the durability of an adhesive bond. Hence, the project starts with a careful characterization of a well-tuned metal oxide. Techniques such as X-ray Photoelectron Spectroscopy (XPS), Visual-light Spectroscopic Ellipsometry (VISE), Contact Angle and Atomic Force Microscopy (AFM) will be used to fully describe the metal oxide layer. By using (ultra)thin polymer films in combination with dedicated top surface (vacuum) techniques and varying thickness polymer layers for the vibrational spectroscopy technique, we will be able to get access to the hybrid system’s common interface and unravel the bonding and structure of the organic compounds near the oxide. Ultrathin polymer layers will be synthesized by spin coating and reactive adsorption because the probing depth of the dedicated top surface (vacuum) analysis technique is of the order of 10 nanometer. To investigate the influence of external conditions such as the direct influence of water or ionic compounds and heat treatments, a new generation of techniques will be used. A combination of FTIR Kretschmann geometry and Odd Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS) will simultaneously provide information on the water and/or ion ingress at the interface and of the whole polymer/metal oxide system. Another technique to study this is Near-Ambient Pressure or NAP XPS. This is a novel technique allowing to investigate samples in “real-world” conditions and it is not yet used to characterize interfacial bonding. This technique gives the prospect to follow chemically the diffusion of e.g. water in the polymer and the influence on the bonds of polymers with the oxide surface. (iii) Collaborating Research Groups The research group SURF at Vrije Universiteit Brussel will be the host department for this project. The FTIR Kretschmann measurements will be conducted at the corrosion research lab in the 3mE faculty at TU Delft. For the hands-on training of the NAP XPS device, the researcher will go to the Lawrence Berkeley National Laboratory for 6 months under the supervision of doctor Hendrik Bluhm. Here, the researcher will gain experience on both a lab-scale and synchrotron NAP XPS setup. The experiments will be continued at the Max Planck institute in Düsseldorf where a lab-scale NAP XPS system is installed. The suggested approach will lead to a full fundamental understanding of the bonding mechanism at the interface between polymer/oxide systems in a wide range of environmental conditions.

Keywords:metal coating, organic coating, Chemistry

Disciplines:Transition metal chemistry

Project type:Collaboration project