Nanoémulsions auto-assemblées par des méthodes physico-chimiques

Abstract : The purpose of this work is to lure a system away from its equilibrium state and trap it into other non-equilibrium states. The systems investigated are (oil+water+amphiphile) or (polymer+good-solvent+bad-solvent). The aim is to avoid macroscopic phase separation and restrain it to the microscopic scale, in order to obtain uniform collections of size-controlled droplets. The approach is to use physicochemical methods, which use interaction constraints between the molecules to self-assemble the droplets. A first scenario is to take the system along equilibrium states until a bifurcation leading to a trapped state, while the equilibrium states move far away. It is observed when water is rapidly added to a (oil+amphiphile) solution. A second scenario is to take the system slightly above equilibrium states, through shear, to reach a trapped state, while the equilibrium states move far away. It is encountered when changing the surfactant layer hydration through physical parameters such as temperature, pH or ionic strength. A third scenario is to push the system towards equilibrium but raise increasingly high barriers as it evolves. This corresponds to the solvent-shifting technique where coalescence, which ultimately leads to macroscopic phase separation, is increasingly hindered by ionic repulsions. Two novel types of pathways have also been identified in this work, contact ripening, which corresponds to molecular exchange at droplets contact, and hindered coalescence, which corresponds to coalescence limited by the droplets approach. The origin of ionic barriers in purified systems has also been elucidated.
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Contributor : Kevin Roger <>
Submitted on : Friday, December 20, 2013 - 5:23:25 PM
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  • HAL Id : pastel-00921639, version 1

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Kevin Roger. Nanoémulsions auto-assemblées par des méthodes physico-chimiques. Chimie-Physique [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2013. Français. ⟨pastel-00921639⟩

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