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International audience; Frozen complex coacervate core micelles (C3Ms) were developed as a class of particle stabilizers for Pickering emulsions. The C3Ms are composed of a core of electrostatically interacting weak polyelectrolytes, poly(acrylic acid) (pAA) and poly(dimethylaminopropylacrylamide) (pDMAPAA), surrounded by a corona of water-soluble and surface active poly(N-isopropylacrylamide) (pNiPAM). Mixing parameters of the two polymer solutions, including pH, mixing method, charge ratio, and salinity of the medium, were carefully controlled, leading to monodisperse, colloidally stable C3Ms. A combination of dynamic light scattering and proton nuclear magnetic resonance experiments showed that the C3Ms gradually disassembled from a dynamically frozen core state in pure water into free polyelectrolyte chains above 0.8 M NaCl. Upon formulation of dodecane-in-water emulsions, the frozen C3Ms adsorb as particles at the droplet interfaces in striking contrast with most of the conventional micelles made of amphiphilic block copolymers which fall apart at the interface. Eventually, increasing the salt concentration of the system triggered disassembly of the C3Ms, which led to emulsion destabilization.

We report on the synthesis of stimulable microgels that are used as building-block for colloidal assemblies in dispersions or at interfaces. To achieve this goal, we synthesized thermosensitive poly(N-isopropylacrylamide), PNiPAM, microgels copolymerized with poly(ethyleneglycol) grafts bearing either a hydroxyl (PEGMAOH) or a terpyridine (PEGMATpy) terminated function. The incorporation and localization of the PEGylated grafts within the microgels network enables a control on both the size and colloidal stability of the microgels without changing their thermosensitivity. The functionalized microgels were then used as building-blocks to build assemblies in dispersions by means of metallo-supramolecular interactions. These interactions are induced by the formation of coordination complexes, [MIITpy2]2+, between the terpyridine functions of the microgels and metallic cations (FeII, CoII, …). We studied the effects of physico-chemical parameters such as salinity, temperature, pH, addition of a depletant polymer on the formation of inter-microgels assemblies. The stimulability via an oxidative medium of the supramolecular interactions allows to dissociating the assemblies into individualized microgels in solution. The formation of [MIITpy2]2+ complexes also allows the synthesis of supramolecular microgels, supra-MG, which internal structure is maintained by supramolecular crosslinks. These microgels, which network structure can be cleaved, are used as emulsifiers of Pickering-Ramsden emulsions. The liquid-liquid dispersions can be destabilized on demand by electrochemical stimulation., Nous avons élaboré des microgels stimulables pouvant servir de briques élémentaires pour des assemblages colloïdaux en dispersion ou aux interfaces. Pour cela, des microgels thermosensibles de poly(N-isopropylacrylamide), PNiPAM, co-polymérisés avec des greffons poly(éthylèneglycol) terminés par une fonction soit hydroxyle (PEGMAOH) soit terpyridine (PEGMATpy) sont synthétisés. L’incorporation et la localisation des greffons PEGylés dans le réseau des microgels permet de contrôler la taille et la stabilité colloïdale des microgels sans affecter leurs propriétés thermosensibles. Les microgels fonctionnalisés sont utilisés comme briques élémentaires pour former des assemblages en dispersion via des interactions métallo-supramoléculaires. Ces interactions sont induites par la formation de complexes de coordination, [MIITpy2]2+, entre les fonctions terpyridine portées par les microgels et des cations métalliques (FeII, CoII, …). L’effet de paramètres physico-chimiques tels que la salinité, la température, le pH, l’ajout d’un polymère déplétant sur la formation d’assemblages entre microgels est étudié. La stimulabilité des interactions supramoléculaires en milieu oxydant permet de dissocier les assemblages formés en microgels individualisés en solution. La formation des complexes [MIITpy2]2+ permet également la synthèse de microgels supramoléculaires, supra-MG, dont la structure interne est contrainte par des points de réticulation supramoléculaires. Ces microgels dont la structure interne est clivable sont utilisés comme émulsifiants d’émulsions de type Pickering-Ramsden pouvant être déstabilisées par stimulation électrochimique.