International audienceCovalent surface modification of conductive, semiconductive, and insulating substrates with thin organic polymers films induced by redox activation of aryl diazonium salts in the presence of vinyl monomers has been investigated in acidic aqueous media. This new process, called diazonium-induced anchoring process (DIAP), is an efficient technique to impart covalent adhesion of polyvinyl coatings onto raw inorganic or organic surfaces without any conductivity requirement. Typically, aryl diazonium salts are reduced with iron powder to give surface-active aryl radicals leading (i) to the formation of a grafted polyphenylene-like film on the substrate surface and (ii) to the initiation of the radical polymerization of the vinylic monomer in solution. The resulting radical-terminated macromolecular chains formed in solution are then able to react with the polyphenylene primer layer to form a very homogeneous thin organic film on the surface. The final organic thin coating is strongly grafted on materials surfaces, as evidenced by its persistence after a long ultrasonic treatment in a good solvent of the polymer. We speculate this process is supported by the large concentration of aryl and hydrogen radicals formed when iron powder is added in the acidic aqueous solution. The thickness of the polymer film can be controlled as a function of time, typically a few minutes, and was measured between 10 and several hundred nanometers. Infrared reflection–absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and contact angle measurements were used to characterize the surface modification of metals, glass, carbon nanotubes, or polytetrafluoroethylene (PTFE). This very simple and efficient grafting method provides a powerful tool for the covalent coating of organic or inorganic surfaces possessing complex geometrical shapes

We report for the first time on grafting of poly(n-methyl methacrylate), (PMMA), and polystyrene (PS) brushes by ATRP from the surface of aligned multiwalled carbon nanotubes (MWCNT) which were electrochemically treated with brominated aryl groups based on diazonium salts. The polymer brushes formed amorphous coatings, as evidenced by high-resolution transmission electron microscopy, by comparison to the nanotube structure. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of PS and PMMA by their characteristic C1s and valence band features. Well-aligned MWCNT network allowed us to sheath individual MWCNTs with polymer brushes while keeping the initial MWCNT alignment structure. This method opens up new avenues for the elaboration of polymer/NT hybrids.

It has already been shown that sono-electrodeposition can be used to coat activated carbon fiber cloth (ACC) with calcium phosphates (CaP) and we recently demonstrated that cathodic polarization at-1 V / Hg/Hg2SO4 was the best parameter to obtain a carbonated calcium deficient hydroxyapatite (CDA) coating with optimal uniformity and homogeneity. In the present study, we investigated whether this technique was suitable to dope this carbonated CDA coating by partial substitution with another bivalent cation such as strontium. We show here that a strontium-substituted carbonated CDA coating can be produced and quantitatively controlled up to at least 10 at.%. In this range we demonstrate that the presence of strontium does not modify either the textural or the structural properties of the carbonated CDA. Owing to the well-known effect of both carbonated CDA and strontium in bone formation, the biocompatibility of ACC coated or not with carbonated CDA or with strontium substituted carbonated CDA was tested using primary human osteoblasts. Our data revealed a positive and dose-dependent effect of strontium addition on osteoblast activity and proliferation. In conclusion, we show here that electrodeposition at-1 V is a suitable and easy process to incorporate cations of biological interest into CaP coating.

No abstract