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Effet de confinement de l’eau dans les verres bioactifs : relation structure propriétés

Abstract : The use of nanostructured mesoporous silica gels for the confinement of functional nano-objects or liquids is a very active area of research with potential applications in various fields. However, the confinement might affect the properties of these nanomaterials and thus their potential applications, depending both on the nature of the liquids used and on the properties of the host materials. In this context, bioactive glasses are porous systems in which physiological fluids are confined. These biomaterials are increasingly studied in view of their frequent application in orthopedic and reconstructive surgery. The biomedical applications of these bioactive glasses are mainly due to their high biocompatibility and high reactivity with the human physiological environment, since the reaction products obtained from these bioactive glasses and the physiological fluids lead to the deposition of a layer of crystalline bone-like carbonate calcium phosphate (Hydroxy-Carbonate Apatite) on their surface shortly after interaction. This hydroxyapatite layer allows the adhesion to the biological substrate, and hence to reconstruct damaged bones.Since these materials are intended to interact with body fluids, the understanding of the impact of confinement on the organization and diffusion of the encapsulated physiological fluids is crucial for improving their properties. Given that the physiological fluids are composed mainly of water, we have focused our investigations to study the structure and properties of water confined in bioactive glasses as model systems. In this thesis work, we propose to tackle this problem by specific experimental methods, primarily by total X-ray scattering coupled with pair distribution function (PDF) analysis. Complementary characterizations by differential scanning calorimetry (DSC) and atomistic simulations based on the Monte Carlo method are used to corroborate the structural models obtained from the PDF analysis. To better understand the impact of size reduction and the influence of host matrix textural properties on the structural and physical properties of confined liquids, we have applied our multi-scale approach to other model systems such as MCM-41, and SBA-15.The total X-ray scattering measurements have been performed as a function of temperature for the different studied nanomaterials while for the numerical simulations the Empirical Potential Structure Refinement (EPSR) code was used. The obtained results indicate a non-homogeneous structuring of the water confined within the silica nanopores. We have shown that the structural organization of confined liquids depends on pore size, water-loading ratio and the textural properties of the host nanomaterials. Furthermore, the partial pair distribution function analysis show that liquids confined in large pores, (pore diameter > 5 nm), have three phases. However, only one distorted phase was observed in the matrices with narrower pores.
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Hassan Khoder. Effet de confinement de l’eau dans les verres bioactifs : relation structure propriétés. Physique [physics]. Université de Lorraine, 2020. Français. ⟨NNT : 2020LORR0106⟩. ⟨tel-02976529⟩

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