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Séminaire « Matière molle : organisation et dynamique »

When do emulsions become multiple and why ? - Patrick Guenoun - Mardi 29 avril 2014 à 11 h

Patrick Guenoun - Laboratoire LIONS - CEA Saclay

Mardi 29 avril 2014 à 11 h - INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-23, 3e étage, salle 317

Abstract

Block copolymers made of a hydrophobic moiety and a thermosensitive polyelectrolyte moiety are shown to be excellent stabilizers for emulsions [1]. By changing pH or temperature, the nature of the emulsion can be easily inverted (oil in water, water in oil). For some definite architectures, these polymers also form very stable multiple emulsions in one step where the polymer is the only single surfactant [2]. These multiple emulsions are found close to the inversion line and are associated with a low surface tension. By studying the microemulsions which are associated to the emulsions with light scattering, neutron scattering and cryoTEM, the interfacial behavior of the polymer associated to different emulsion structures was determined. Strong differences are observed as a function of polymer architecture (diblock, statistical) and polyelectrolyte ionization (pH). The nature of the emulsions is more reliably predicted by the conformation (when determined) than by the polymer partitioning between oil and water (Bancroft rule). However the latter rule is shown to be more effective to predict multiple emulsions.

[1] Marchal F, Roudot A, Pantoustier N, et al., J. Phys. Chem. B 111 (2007) 13151.
[2] Besnard L, Marchal F, Paredes J.F, Daillant J, Pantoustier N, Perrin P, Guenoun P, Advanced Materials 25 (2013) 2844.

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