Les nano-objets hybrides ou polymères connaissent un intérêt grandissant depuis plusieurs années mais peu sont étudiés sous irradiation. Dans ce travail, différents nano-objets ont été synthétisés et étudiés pour comprendre leur stabilité face à des rayonnements ionisants. Nous avons étudié l’effet de l’irradiation sur des copolymères à blocs amphiphiles pouvant s’organiser en micelles dans l’eau. Les objets varient par la nature de leur polymère hydrophobe et leur sensibilité aux rayonnements ionisants. Dans un cas, des polyméthacrylates ont été copolymérisés par ATRP à partir d’un PEG macro-amorceur. Dans un autre cas, pour accentuer l’effet de l’irradiation, un polysulfone aliphatique plus radiosensible, a été synthétisé via une polyaddition thiol-ène. Après nanoprécipitation, les objets ont été caractérisés avant et après irradiation par des techniques de diffusion et de chromatographie. En parallèle, on s’est intéressés également à des nanoparticules métalliques connues pour augmenter l’effet de l’irradiation. Des nanoparticules d’or greffées de polymères ont été synthétisées par voie « grafting to » après synthèse de macro-ligands par polymérisation radicalaire contrôlée. Après une caractérisation fine des objets, l’effet de l’irradiation a été étudié à la fois sur la taille des objets et la masse des polymères afin de déterminer la nature des phénomènes mis en jeu. / Hybrid and polymer nano-objects have known a growing interest these last years but few are studied under irradiation. In the present work, different nano-objects have been synthetized and studied to understand their stability towards ionizing rays. We have studied the effect of irradiation onto amphiphilic bloc copolymer that form micelles in water. Objects were varied by the nature of their hydrophobic bloc and their sensibility to ionizing rays. First, methacrylates were copolymerized by ATRP with a PEG macro-initiator. Secondly, to improve radiation effect, a more radiosensitive polymer, a polyolefinsulfone, was synthetized by a thiol-ene polyaddition. After nanoprecipitation, objects were caracterized before and after irradiation by scattering and chromatography techniques. In parallel we also studied metallic nanoparticles well known for improving irradiation effect. Polymer-grafted gold nanoparticles were synthetized via a “grafting to” technique, after the synthesis of macro-ligands by controlled radical polymerization. After a precise characterization of these objects, irradiation effect has been studied via changes in size and polymer mass. This will permit to determine the nature of induced phenomena.

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Ph. D. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Driven by the need of sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)]. Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Visualization and imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction, energy-dispersive X-ray spectroscopic analysis confirmed the formation of Pd on the modified MNS surface. An estimate of 5.0 nm for crystallite size was calculated by application of the Scherrer equation. The composite material, denoted Pd@PEI-MNS, exhibited catalytic activity in formic acid-mediated Cr(VI) reduction. Through a one-factor-at-a-time experimental design, the activity of the Pd@PEI-MNS was illustrated to be dependent on solution pH; initial Cr(VI) concentration, initial formic acid concentration, and presence of competing anions; Pd@PEI-MNS dose; and temperature. Subsequent modeling of the Cr(VI) removal process by response surface methodology revealed that the most influential factor was Pd@PEI-MNS dose followed by temperature and formic acid concentration. The influence of initial Cr(VI) concentration, was surpassed by the dose-temperature and dose-formic acid concentration interactive effects. Elucidation of the Cr(VI) removal mechanism by XPS and FTIR demonstrated the active participation of surface -CH2OH functional groups, the bulk of which originated from the reduction of esters of the grafted ligands. Replacement of formic acid to carbon dioxide, the -CH2OH groups were converted to -COO- groups.

To produce a greener adhesive is always an issue of concern to the commercial market and global environment. The environmental request for producing greener and bio-based adhesives leads to an increased awareness of replacing fossil-based components in adhesives with bio-based alternatives. Consequently, many researchers try to graft polymers from natural materials and some achievements have been made. In this work, an improved procedure to graft vinyl acetate (VAc) from chitosan (CS) is proposed and significant improvements were made regarding the increased Tg and water resistance. The achieved monomer conversion of VAc was ~97 %, and it was confirmed that chitosan-graft-poly(vinyl acetate) (CS-g-PVAc) could be used as a wood adhesive. The adhesive exhibited competitive properties to commercial PVAc wood adhesive. In the produced CS-g-PVAc, ~17 % of the fossil-based content of VAc could be replaced with bio-based chitosan, indicating an increased sustainability. At the same time there is no residual monomer during pressing, which avoid to pollute environment and hurt human. Compared to commercial PVAc, which has Tg at ~28 ℃, the Tg of CS-g-PVAc is ~42 ℃ At the same time, the water resistance of PVAc adhesive was successfully increased.