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Developement of an "all-in-one" approach for the synthesis of silica-based hybrid materials

Abstract : In this work, we investigated the synthesis of new organosilane precursors and their polymerization to silica hybrid materials with REE extracting properties via an all-in-one approach.To reach this goal, five organosilane precursors were synthetized in good yield. First, these new precursors were used to elaborate dense silica hybrid materials (SHM). The characterization of the local structure by FTIR and of the mesostructure by SAXS of the SHMs highlighted the link between the chemical and physical interactions between the headgroups of the precursors and the others species existing in the reaction mixture. These interactions drive the local connectivity of the siloxane network and the mesostructure of the obtained materials (lamellar and 2D hexagonal phases). Second, in order to improve the material properties, an innovative approach in two steps was proposed. The first step was based on the structuring of binary alcohol/water mixtures to influence the aggregation behavior of silica nanoparticles prepared from tetraethyl orthosilicate (TEOS). Here, a remarkable specific surface area of 2000 m2 g-1 was achieved. In a second step, the reaction conditions that lead to materials with the highest specific surface area were used in combination with the synthesized organosilane precursors. The results show the potential of this approach to tailor the properties of the obtained materials. Finally, the SHMs synthesized from the pure organosilane precursors were successfully tested for the selective and efficient extraction of rare earth elements present in a simulated leachate of NdFeB magnets.This work offers promising prospects for the "all-in-one" synthesis of SHMs with direct applications.
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Robert Winkler. Developement of an "all-in-one" approach for the synthesis of silica-based hybrid materials. Other. Université Montpellier, 2019. English. ⟨NNT : 2019MONTS075⟩. ⟨tel-02479604⟩

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