Émulsions de Pickering : approche théorique et applications : analyse physico-chimique des phénomènes interfaciaux : obtention d'émulsions de Pickering nanométriques de manière spontanée et d'émulsions foisonnées de Pickering

Abstract : Pickering emulsions are emulsions stabilized by solid particles in opposition to emulsifiers-stabilized emulsions. The stabilization of Pickering emulsions comes from a strong adsorption of solid particles at the oil-water interface that builds a rigid barrier against coalescence. The aim of this work was to understand, develop and optimize methods for the fabrication of different types of Pickering emulsions stabilized by silica nanoparticles. Three mains axes can be exposed: (i) Firstly, a theoretical approach on the physico-chemical interfacial phenomena of Pickering emulsions stabilized by non-aggregated individual silica nanoparticles. Adsorption as mono- or multi-layers can be reached depending the Oil/Silica ratio. Two behaviors were observed: At high oil/silica mass ratio, the oil/water interface was covered by a monolayer of nonaggregated silica particles. Stable emulsions were stabilized by a monolayer of silica particles at 54% coverage of the oil droplets surface. Oil droplet diameter depends on formulation parameters. Adsorption as multilayers was reached at lower oil/silica mass ratio and oil droplet diameter depends on fabrication process. (ii) Droplets diameters could be reduced thanks to various processes in order to obtain Pickering nanoemulsions, also called NanoPickering. The first step was to test the viability of such emulsions using a high energy process (sonication). Then, a low energy process (nanoprecipitation) was used. Stable Pickering nanoemulsions can be made on more than one month. However, the oil quantity obtained in the final media is low (less than 1wt%). (iii) In parallel, a new application was developed allowing the formulation of Pickering aerated emulsions, totally stabilized by nanoparticles. Two types of Pickering whipped emulsions can be made. One which has high air content or one which has a stable height, thanks to a gelification phenomenon. This occurs after a macroscopic change of state. All of these results confirm that Pickering emulsions offer the opportunity to discover new applications made by innovative processes. For instance, NanoPickering made by spontaneous emulsification, or Pickering whipped emulsion fully stabilized without emulsifiers. Moreover, theoretical approaches and interfacial phenomena studies are still current scientific questions
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Laure Ridel. Émulsions de Pickering : approche théorique et applications : analyse physico-chimique des phénomènes interfaciaux : obtention d'émulsions de Pickering nanométriques de manière spontanée et d'émulsions foisonnées de Pickering. Chimie théorique et/ou physique. Université Claude Bernard - Lyon I, 2015. Français. ⟨NNT : 2015LYO10176⟩. ⟨tel-01260157⟩

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