UV-visible light: A novel route to tune the type of an emulsion

The light-induced control of the type (oil or water continuous medium) of emulsions stabilized by an appropriate combination of two polyelectrolyte surfactants is described in this paper. Due to its balanced hydrophilic-lipophilic properties, the first polymeric emulsifier (denoted BHL) has the ability to stabilize both direct and inverse emulsions and play the role of the main emulsifier of the n-dodecane-water system. The second one is a photoresponsive amphiphilic polymer (PR polymer) used at such low concentrations that the sole presence of the PR polymer as an emulsifier leads to the formation of unstable emulsions. The chromophore groups randomly distributed along the PR polymer backbone enable the adjustment of its HL properties upon irradiation by near-UV light. We demonstrate that the change in hydrophobicity of the PR polymer induced by irradiation can be suitably used to tune the type of the liquid-liquid dispersion containing both polymers. Consequently, UV-visible light is presented as a novel trigger to control the emulsion type.