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Particules déformables pour stabiliser et déstabiliser des émulsions

We have synthesized and used thermoresponsive microgels of PNIPAM to stabilize oil/water emulsions. The particles have a well-defined diameter equal to 800 nm at ambiant temperature and shrink down to a diameter of 400 nm at 40°C. Indeed, water is expulsed from the particles as the PNIPAM chains switch from good to bad solvent conditions. We found that emulsions are stable below 32°C, which corresponds to the LCST of PNIPAM chains but above this temperature, the emulsions spontaneously destabilize. Optical microscopy as well as oil/water interfacial measurements have been performed to understand as the mechanism of destabilization of the emulsions. Moreover at high temperature, we have found that the gel particles aggregate at the oil-water interface to form a macroscopic aggregate (see picture). At the scale of the emulsion droplets, the interfacial layer is probably highly heterogeneous, which accelerates coalescence of the drops.

Macroscopic aggregate of microgels at the oil-water interface formed above the LCST of PNIPAM. The width of the aggregate is 1cm.

C. Monteux, C. Marlière, P. Paris, N. Pantoustier, N. Sanson, P. Perrin, Langmuir, 2010, 26, 13839. link