Branched Copolymer Surfactants as Versatile Templates for Responsive Emulsifiers with Bespoke Temperature‐Triggered Emulsion‐Breaking or Gelation

Abstract It has been found that the thermoresponsive behavior of emulsions stabilized by block copolymer surfactants (BCSs) can induce either gelation or emulsion break‐up with mild temperature changes. A hydrophilic, steric‐stabilizing component of the BCS, polyethylene glycol methacrylate (PEGMA), is crucial to control the thermoresponsive behavior of the emulsions: longer PEG chains (950 g mol⁻¹) lead to thermoregulation, whereas shorter PEGM chains (500 or 300 g mol⁻¹) lead to emulsion break‐up upon mild heating. Additionally, the relative abundance of PEGMA to the thermoresponsive component in the BCS controls the gelation temperature of BCS‐stabilized emulsions. Small‐angle neutron scattering and transmission electron microscopy reveal that the BCS forms oblate ellipsoids which grow anisotropically with temperature. In samples that form a gel, there is evidence that these nano‐objects form supra‐colloidal structures, which are responsible for the gel mesophase formation. An optimal BCS can form emulsions that transition from a liquid to gel state when warmed above 32 °C. This makes the system ideal for in situ gelation upon contact with the body. Overall, this study highlights the great potential of BCSs in generating thermoresponsive emulsions for drug delivery and other healthcare applications.