Sébastien Devillers

Induction heating Vs conventional heating for the hydrothermal treatment of nitinol and its subsequent 2-(Methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate coating by surface-initiated atom transfer radical polymerization

Nitinol is an alloy of great interest in general and especially in the biomedical field where many researches are aimed to improve both its corrosion resistance and its biocompatibility. In this work, we report on the advantage of an induction heating treatment in pure water compared to a conventional hydrothermal procedure. Both treatments lead to a hydroxylation of the surface, a decrease of the nickel amount in the outer part of the oxide layer, and a drastically decreased corrosion current density. However, the amount of surface hydroxyl groups is higher in the case of the induction heating treatment, which in turn leads to a denser grafting of atom transfer radical polymerization initiators and ultimately to a thicker 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC) polymer layer than in the case of conventional heating treatments. X-ray photoelectron spectroscopy (XPS), static contact angle, and polarization curves measurements as well as scanning electron microscopy (SEM) have been used to characterize the obtained modified surfaces.

Induction heating for surface triggering styrene polymerization on titanium modified with ATRP initiator

Titanium and its alloys present high interests for technological applications due to their high corrosion resistance, mechanical properties and biocompatibility. In combination with these remarkable characteristics, some Ti applications require specific surface properties that can be imparted with suitable surface functionalizations of the TiO(2) oxide layer. The present work aims to study the surface-initiated ATR polymerization of styrene on titanium substrates, using grafted 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid as initiator and to compare the impact of two different heating ways on the efficiency of this polymerization: induction vs. conventional heating. The ability of the initiator to bind titanium substrates and act as an initiator for ATRP of styrene is investigated: both heating conditions led to the polymerization of styrene on modified titanium substrates. However, induction heating appeared to be much more efficient than conventional heating, leading to the formation of a thicker, much denser polystyrene layer than conventional heating after only 1h of polymerization.

1-Dodecanethiol Self-Assembled Monolayers on Cobalt

Cobalt and its alloys are used in a broad range of application fields. However, the use of this metal is especially limited by its strongly oxidizable nature. The use of alkanethiol self-assembled monolayers (SAMs) is a very efficient way to protect against such oxidation and/or to inhibit corrosion. This surface modification method has been particularly applied to oxidizable metals such as copper or nickel, yet the modification of cobalt surfaces by alkanethiol SAMs received limited attention up to now. In this work, we study the influence of parameters by which to control the self-assembly process of 1-dodecanethiol monolayers on cobalt: nature of the surface pretreatment, solvent, immersion time, and concentration. Each of these parameters has been optimized to obtain a densely packed and stable monolayer able to efficiently prevent the reoxidation of the modified cobalt substrates. The obtained monolayers were characterized by X-ray photoelectron spectroscopy (XPS), polarization modulation infrared reflection-absorption spectroscopy, and contact angle measurements. The stability of the optimized 1-dodecanethiol monolayer upon air exposure for 28 days has been confirmed by XPS.

Synergistic effect on corrosion resistance of Phynox substrates grafted with surface-initiated ATRP (co)polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-hydroxyethyl methacrylate (HEMA).

Phynox is of high interest for biomedical applications due to its biocompatibility and corrosion resistance. However, some Phynox applications require specific surface properties. These can be imparted with suitable surface functionalizations of its oxide layer. The present work investigates the surface-initiated atom transfer radical polymerization (ATRP) of 2-methacryloyoxyethyl phosphorylcholine (MPC), 2-hydroxyethyl methacrylate (HEMA), and ATRP copolymerization of (HEMA-co-MPC) (block and statistic copolymerization with different molar ratios) on grafted Phynox substrates modified with 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) as initiator. It is found that ATRP (co)polymerization of these monomers is feasible and forms hydrophilic layers, while improving the corrosion resistance of the system.

New semifluorinated dithiols self-assembled monolayers on a copper platform.

New alpha,omega-semifluorinated dithiols HS-(CH2)11-(CF2)n-(CH2)11-SH, called DTn, and corresponding dithioacetate molecules CH3COS-(CH2)11-(CF2)n-(CH2)11-SCOCH3, called DTAn ( n = 4, 6, 8), were synthesized and used to create self-assembled monolayers (SAMs) on both untreated copper surfaces and electrochemically reduced ones. The aim of this study is to assess the organization of the resulting SAMs, particularly the effect of the presence of two perhydrogenated segments surrounding the perfluorinated one, and the ability of these difunctional molecules to bind copper substrates by only one end per molecule. In each case, the organization of the SAM is rather poor and only DTA8 molecules seem to adopt an upright position on reduced copper. In addition, the layers have been investigated by cyclic voltammetry (CV) to assess their coverage. DT4 SAMs reveal a covering ratio higher than 99%.

Grafting PEG Fragments on Phynox Substrates Modified with 11-Phosphoundecanoic Acid

Phynox, a cobalt-chromium alloy, exhibits interesting mechanical properties, making it a valuable material for several applications. However, applications as a biomaterial often require specific surface properties that can be imparted with suitable surface functionalizations. The aim of this work is to functionalize the Phynox surfaces with 11-phosphoundecanoic acid monolayers, creating a platform for a large variety of postgrafting chemical reactions, e.g., with alcohols and amines, to modify and control the surface properties. In the first part, we assess the interaction between the two terminal moieties of the 11-phosphoundecanoic acid and the Phynox surface by studying the grafting of n-dodecylphosphonic acid and n-dodecanoic acid. To illustrate the potential of the 11-phosphoundecanoic acid monolayer, we report on our first attempts to postgraft small poly(ethylene glycol) (PEG) fragments by the Steglich esterification reaction between the carboxylic end of the grafted 11-phosphoundecanoic acid molecules and the alcohol function of PEG fragments.

Electrodeposition of Crystalline Aluminium on Carbon Steel in Aluminium Chloride — Trimethylphenyl Ammonium Chloride Ionic Liquid

Aluminium electrodeposition on carbon steel is performed potentiostatically and galvanostatically from aluminium chloride — trimethylphenylammonium chloride room temperature ionic liquid (RTIL). The influence of the electrochemical parameters and temperature on the coating composition, morphology and corrosion resistance is studied. For each experimental condition, the coatings are composed of metallic crystalline aluminium, contain a small amount of chlorine and a few RTIL cations remain weakly adsorbed on their surface. It is shown that temperature increase favors the growth of aluminium coating but to the detriment of the nucleation and well covering coatings. The galvanostatically formed coatings at low temperature present a corrosion resistance close to that of aluminium.

Morphology and Crystallinity of Electrodeposited Copper Particles on Nickel Controlled by Induction Heating

Templates and capping agents are usually used for the synthesis of NPs with well-defined shape and size. However, the presence of these agents at the surface of the formed NPs may have undesirable effects for some applications. Deposition parameters can also be used to control the morphology and crystallinity of the obtained deposits. Temperature and its gradient are known to play a significant role on the electrodeposition kinetics and thus on the resulting deposit morphology. We have shown in previously published exploratory studies that a mass transport enhancement such as the one obtained in electrochemical systems with heated electrodes can greatly influence the growth kinetics regarding the diffusion limitation aspects. In these works, we compared the morphology of copper particles electrodeposited in two temperature-equivalent conditions i.e. a conventional heating (CH) of the solution (isothermal situation) and an induction heating (IH) of the nickel electrode (non-isothermal situation). The aim of the present work is to further investigate the mechanistic aspects of the galvanostatic electrodeposition of Cu particles on Ni under IH by means of in situ potential and surface temperature measurements correlated with SEM observations of the deposited Cu particles.