The phase inversion of water-toluene emulsions stabilized with a single thermo- and pH-sensitive copolymer occurs through the formation of multiple emulsions. At low pH and ambient temperature, oil in water emulsions are formed which transform into highly stable multiple emulsions at pHs immediately lower than the inversion border. At higher pHs, the emulsion turns into a water in oil one.

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.