title: Emulsion stabilization and inversion using a pH- and temperature-sensitive amphiphilic copolymer.
abstract: We describe how a versatile amphiphilic diblock copolymer can form oil-in-water (o/w) or water-in-oil (w/o) emulsions depending on pH and temperature. At high pH and temperature, this copolymer is mostly hydrophobic and forms w/o emulsions. Its spontaneous curvature is greatly increased upon pH and/or temperature lowering (due to protonation and/or hydration, respectively), which allows the formation of o/w emulsions. Conductivity measurements and confocal fluorescence micrographs evidence the two kinds of structures obtained over a wide range of pH and temperature. We also show how the emulsion type can be reversibly switched along a temperature scan under stirring. The lower stability of the w/o emulsions as compared to the o/w ones is attributed to a lack of electrostatic repulsion. The importance of the copolymer architecture and conformation with regards to droplet stability is discussed.
authors.affiliation: Service de Chimie Moléculaire, LIONS, Bâtiment 125, CEA. Saclay, F-91191 Gif-sur-Yvette Cedex, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Marchal
authors.forename: Angelina
authors.initials: A
authors.lastname: Roudot
authors.forename: Nadège
authors.initials: N
authors.lastname: Pantoustier
authors.forename: Patrick
authors.initials: P
authors.lastname: Perrin
authors.forename: Jean
authors.initials: J
authors.lastname: Daillant
authors.forename: Patrick
authors.initials: P
authors.lastname: Guenoun