Etude de la synthèse et de l'auto-assemblage de copolymères CO2-philes comportant des motifs complexants (application à la décontamination en milieu CO2 supercritique)

Dans le cadre du développement durable, réduire le volume de déchets nucléaires est devenu prioritaire. L'utilisation du dioxyde de carbone supercritique (CO2 sc) peut résoudre cette problématique. L'objectif de cette étude est d'extraire une contamination en cobalt, particulaire ou ionique, déposée sur des blouses textiles. La stratégie repose sur des copolymères CO2-philes/CO2-phobes particulièrement solubles dans le CO2 sc, comportant des groupements complexants. Cette approche couple l'utilisation de polymères pour la stabilisation stérique de particules, de tensioactifs capables de s'auto-assembler pour faciliter l'extraction, et de ligands. La polymérisation radicalaire contrôlée a été utilisée pour synthétiser des copolymères fluorés à gradient ou à blocs. Les courbes de points de trouble de ces copolymères ont été déterminées expérimentalement dans le CO2 sc. La prédiction des diagrammes de phases polymère/CO2 sc a également été abordée par modélisation Perturbed-Chain Statistic Associating Fluid Theory (PC-SAFT). Les copolymères à gradient sont plus avantageux que les copolymères à blocs car ils sont solubles à des pressions et températures plus modérées. La diffusion de neutrons aux petits angles a permis de montrer que l'agrégation des copolymères à gradient est induite par la pression. Leurs propriétés aux interfaces ont ensuite été démontrées: ils peuvent former des microémulsions eau/CO2 sc et stabiliser des dispersions d'hydroxyde de cobalt dans le CO2 sc. Finalement, en présence d'une très faible quantité d'eau, les ions Co2+ ont été extraits avec un taux de 37 % d'une matrice coton/polyester par un copolymère à gradient.In the frame of sustainable development, a priority is to decrease the volume of nuclear wastes. The use of supercritical carbon dioxide (scCO2) could allow to solve this problem. The aim of this study is to extract an ionic or particle cobalt contamination deposited on textile lab coats. The strategy uses copolymers soluble in scCO2 and containing complexing groups. This approach couples the use of amphiphilic copolymers for steric stabilization of particles, of surfactants able to self-assemble to promote extraction and of ligands. Controlled radical polymerization is used to synthesize fluorinated gradient or block copolymers. Cloud point curves of the copolymers are determined experimentally to determine the parameters affecting their solubility in scCO2. Prediction of polymer/scCO2 phase diagrams was approached by Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) modeling. Gradient copolymers appear more advantageous than block copolymers due to their solubility in much milder conditions of pressure and temperature. Small angle neutron scattering (SANS) allowed us to evidence the pressure-induced aggregation of the gradient copolymers in CO2. Their interface properties were demonstrated: they allow to form water-in-CO2 microemulsions and to stabilize cobalt hydroxide dispersions in scCO2. Lastly, thanks to a low amount of gradient copolymer, Co2+ ions were efficiently removed from a cotton/polyester matrixMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Elaboration of double emulsion-based polymeric capsules for fragrance

We aim at encapsulating fragrances made of a variety of lipophilic species to slow down their diffusion. Our strategy is to develop capsules by polymerizing the water intermediate phase of an oil-in-water-in-oil double emulsion. In other terms, our system consists in a direct emulsion of fragrance (O1) in a water phase (W) containing monomer, initiator and cross-linker. To obtain the double emulsion, this direct emulsion, stabilized by a hydrophilic surfactant, is itself dispersed in an external lipophilic solvent used in perfumery (O2) and stabilized by a lipophilic surfactant. Polymerization of the intermediate water phase aims at obtaining a three dimensional network. Differently from nowadays-proposed capsules, this strategy allows polymerization only taking place in the water phase rather in the phase containing the fragrance. Moreover, the obtained 3D network is supposed to play the role of an effective barrier limiting the diffusion of the inner lipophilic species towards either the external solvent or air. Such an approach implies the combination of a formulation step to elaborate the double emulsion using two antagonistic surfactants, a hydrophilic one and a lipophilic one, and of the polymerization of the intermediate phase. Insertion of the polymerizable species in the double emulsion shall not destabilize it. Some monomers exhibiting interfacial affinity and interfering with the formulation of the double emulsion have to be avoided. By varying the nature of the monomers and the cross-linker to monomer ratio, capsules with high encapsulation efficiencies and with various mechanical properties have been obtained

Synthesis of new fluorinated gradient copolymers with complexing groups by RAFT polymerization and their properties in supercritical carbon dioxide

International audienc

Formulation of concentrated oil-in-water-in-oil double emulsions for fragrance encapsulation

We report the formulation of a concentrated double oil-in-water-in-oil (O/W/O) emulsion for fragrance encapsulation.As their water-in-oil-in-water homologous, these O/W/O emulsions, seldom described in literature, also require the use of two antagonist surfactants: a hydrophilic one (HS) to stabilize the fragrance-inwater droplets and a lipophilic one (LS) to stabilize the aqueous globules dispersed in oil, containing themselves the direct emulsion. An important issue in cosmetics is the necessity to adapt the formulation to each fragrance, so that a major progress would be the successful elaboration of an O/W/O emulsion insensitive to fragrance changes. In order to approach such a composition, two model fragrances composed of 10 and 13 molecules representative of the most used molecules in this domain were specially assembled for the study. The aim was to identify possible hydrophilic and lipophilic stabilizers leading to a double O/W/O emulsionsand determine compositions able to encapsulate both fragrances. The double emulsion was prepared by a twostepprocess, allowing varying the double emulsion composition i.e the amount of both surfactants as well asthe quantity of droplets inside the globules. By plotting “feasibility diagrams” we can propose a best compositionshared by the two fragrances. Such a double emulsion is composed of 20 wt% of fragrance dropletswith respect to the globule volume, 75 wt% of globules with respect to the total emulsion, 7.5 wt% of HS withrespect to the intermediate aqueous phase and 10 wt% of LS with respect to external oil phase. The robustnessof this optimized composition against molecule changes was tested using a third fragrance. Then the encapsulatedefficiency was measured showing the high encapsulation rate (close to 99 %) of the selected system

Extraction of Cobalt Ion from Textile Using a Complexing Macromolecular Surfactant in Supercritical Carbon Dioxide

International audienc

Self-organization of gradient and block copolymers with complexing properties in supercritical CO2

6 pagesInternational audienc

Study of an Innovative Nuclear Process Based on Dense CO2: Application to Decontamination and Pu Recovery

International audienc

Use of fluorinated and silicone-based copolymers with complexing groups for applications in supercritical CO2

International audienc

Solubility and Self-Assembly of Amphiphilic Gradient and Block Copolymers in Supercritical CO2

International audienceThis work aims at demonstrating the interest of gradient copolymers in supercritical CO2 in comparison with block copolymers. Gradient copolymers exhibit a better solubility in supercritical CO2 than block copolymers, as attested by cloud point data. The self-assembly of gradient and block copolymers in dense CO2 has been characterized by Small-Angle Neutron Scattering (SANS) and it is shown that it is not fundamentally modified when changing from block copolymers to gradient copolymers. Therefore, gradient copolymers are advantageous thanks to their easier synthesis and their solubility at lower pressure while maintaining a good ability for self-organization in dense CO2

SANS study of the self-organization of gradient copolymers with ligand groups in supercritical CO2

International audienc