Marie-Eve Druart

Free radical-induced grafting from plasma polymers for the synthesis of thin barrier coatings

Plasma polymer films (PPF) are attracting a great deal of attention for application in various fields due to several remarkable properties, such as good adhesion to different substrates, improved mechanical/chemical stability and a high surface reactivity. This reactivity, associated with the presence of free radicals and originating from the PPF growth mechanism based on many fragmentation and recombination reactions, is often, however, a potential source of trouble. Oxidation of the PPF promptly begins in aerobic conditions via reactions of surface free radicals with oxygen molecules and causes a deterioration of its intrinsic properties in the surface region leaving a nonspecifically functionalized surface in the long-term. Recently a novel approach to functionalize plasma polymer films through the grafting reaction initiated from free radicals trapped on the PPF surface was developed. The present work investigates the potential to employ such an approach in a corrosion protection context. Characterization methods, including Electrochemical Impedance Spectroscopy (EIS) tests, demonstrate that the controlled consumption of surface free radicals via polymer grafting, instead of oxidation, has a beneficial effect on the corrosion protection behavior of the PPF layer deposited on clad 2024 aluminum alloy.

A multilayer coating with optimized properties for corrosion protection of Al

In the context of a universal search for alternatives to chromate-based coatings, which are toxic for both human beings and the environment, a multilayer coating for Al protection purposes is developed and investigated in the current work. The first layer is selected to be a hexamethyldisiloxane-based plasma polymer film (PPF), deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD), due to a number of interesting features that are characteristic of plasma polymers. The second layer is synthesized via the polymerization of the 2-ethylhexyl acrylate monomer initiated from the free radicals trapped on the surface of the PPF during its growth. A subsequent layer of a copolymer of 2-ethylhexyl acrylate and glycidyl methacrylate, poly(EHA-co-GMA), is deposited by spin coating to increase the corrosion resistance of the coating. An improvement in the anti-corrosion properties of the multilayer coating by approximately three orders of magnitude as compared to the uncoated Al substrate is observed. Further enhancement of the adhesion and scratch resistance properties is addressed via UV-crosslinking and the incorporation of in situ generated silica nanoparticles into the final layer.

Effect of photo-crosslinking on the performance of silica nanoparticle-filled epoxidized acrylic copolymer coatings

The effect of UV-crosslinking on the morphological, mechanical and barrier properties of a hybrid coating based on an epoxidized acrylic polymer filled with silica nanoparticles, incorporated in situ through the sol–gel method, was studied. A systematic comparison of coatings loaded with various amounts of silica nanoparticles subjected or not to UV-curing was reported. The morphological and mechanical properties were investigated by atomic force microscopy (AFM) and tribology tests, while the corrosion resistance of thin films applied on aluminum alloys was measured by electrochemical impedance spectroscopy (EIS). Our findings indicate that a synergic effect is brought about by the combination of silica nanoparticles and UV-curing, significantly enhancing the mechanical properties of the coating, although the corrosion protection was compromised. The resulting coating may be used in applications requiring high mechanical performance.

Development of mesoporous sol–gel films for antifingerprint applications on glass

AbstractMesoporous films were synthesized by specific sol–gel route, including the use of surfactant molecules acting as templating agent through the evaporation induced self-assembly process. Controlled mesoporosity of the film is obtained by the thermal removal of the templating agent. In this work, the mesostructure of the sol–gel layer is used as reservoir for active enzymatic molecules providing antifingerprint coating. The mesopore size and their configuration were designed to assure a good impregnation by lipases. The coatings were applied on glass. The influence of the deposition process and the composition of the sol–gel on the structure of the mesoporous film was investigated. The film morphology was characterized by scanning electron microscopy and water adsorption/desorption isotherms recorded with a quartz crystal microbalance. The stability of the sol–gel solution was assessed by rheological measurements. The efficiency of the combination of mesoporous film and the enzymatic solution was determined in terms of antifingerprint properties using an artificial sebum. Mesoporous sol–gel film is used as reservoir for active enzymatic biomolecules to provide antifingerprint coating. Mesoporous structure is obtained by the sol–gel method using the evaporation induced self-assembly process. Different parameters (thickness of coating, concentration in templating agent, etc.) were studied to manage and adapt the size and the structure of the mesopores in order to obtain an active coating.HighlightsDesign of mesoporous sol–gel films using evaporation induced self-assembly process.Influence of the thickness, deposition method, and templating agent/precursor molar ratio on the mesoporosity.Evaluation of antifingerprint properties of the sol–gel films impregnated with enzymes.