Gelling Colloids Through Thermally-Triggered Surfactant Displacement

Colloidal system undergoes gelation shows interesting rheological properties and is a powerful tool for applications in tissue engineering, food industry and porous material design. Interparticle interaction that can be finely tune results in the great possibility to engineer the material rheology and microstructures. Traditional gelation strategy replies on the manipulation of attractive interaction such as depletion, polymer bridging and dipole-dipole interaction. Here, using the nanoemulsion as a model colloidal system, we present a platform where the colloidal gelation is induced by the decrease in repulsive interaction via a thermally-triggered surfactant displacement mechanism. By adding amphiphilic oligomer surfactants into an oil-in-water nanoemulsion system, the ionic surfactants on the nanoemulsion droplets are replaced by the oligomers at elevated temperatures, leading to a decrease in electrostatic repulsion. The resulting material shows rich rheological properties, and the gelling mechanism is robust over a wide range of nanoemulsion formulations. Our stimuli-responsive gelation platform is general and provides a new degree of freedom to engineer complex soft materials.