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Séchage de nanocomposites à base de poly(acide méthacrylique) et de nanoparticules de silice, de la solution au solide

Abstract : The dispersion of nanoscale inorganic fillers within a polymer allows to modulate the mechanical properties of a material. One of the ways used to prepare these nanocomposite materials relies on solvent evaporation. The purpose is to monitor the drying of these materials and to study their evolution from the semi-dilute solution towards the solid state. The results obtained should help understanding the mechanisms involved during drying, their impact on the charge organization and on the mechanical behavior of the final nanocomposites. A stimulable system composed of a polymer matrix and a filler is used to modulate the interactions at the matrix-filler interface. A polyelectrolyte, poly (methacrylic acid), is used: its charge rate and conformation vary from neutral and globular at pH=3 to fully negatively charged and expanded conformation at pH=9. Silica nanoparticles with three different surface modifications are chosen in order to modify polymer adsorption on nanocharges.A first work is carried out in aqueous solutions to obtain information on the structuring of these systems in the semi-dilute regime and under conditions close to thermodynamic equilibrium. Phase diagrams of each system are analyzed by small angle X-ray scattering (SAXS). It allows determining the distribution of silica at nanoscale. In order to understand the structuring processes during drying, two drying experiments in confined geometry are performed. The first is at the macroscopic length scale and concerns the drying of a drop. It allows the follow of the morphology but also of the polymer concentration at different stages of drying. The second is at the nanoscale where in-situ structural characterizations are carried out by SAXS during the drying process of a confined drop. The formation and evolution of the structures formed by the silica nanoparticles are studied during the drying of samples involving three types of silica and prepared at three pH values.Bulk materials are prepared at longer drying time and then structurally and mechanically characterized by combining SAXS, Atomic Force Microscopy (AFM) and microindentation techniques. The mechanical properties analyzed at several size scales (nanometric and micrometric) are compared for two materials prepared at pH=3 and pH=9. The degree of reinforcement of the elastic modulus is correlated to the structure formed by the silica nanoparticles
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Submitted on : Friday, January 1, 2021 - 1:13:56 AM
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  • HAL Id : tel-03091985, version 1



Azad Erman. Séchage de nanocomposites à base de poly(acide méthacrylique) et de nanoparticules de silice, de la solution au solide. Matériaux. Université Paris-Est, 2019. Français. ⟨NNT : 2019PESC1033⟩. ⟨tel-03091985⟩



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