Self-Regulated Nanoparticle Assembly at Liquid/Liquid Interfaces: A Route to Adaptive Structuring of Liquids

The controlled structuring of liquids into arbitrary shapes can be achieved in biphasic liquid media using the interfacial assemblies of nanoparticle surfactants (NP-surfactants), that consist of a polar nanoparticle “head group” bound to one or more hydrophobic polymer “tails”. The non-equilibrium shapes of the suspended liquid can be rendered permanent by the jamming of the NP-surfactants formed and assembled at the interface between the liquids as the system attempts to minimize the interfacial area. While critical to the structuring process, little is known of the dynamic mechanical properties of the NP-surfactant monolayer as it is dictated by the characteristics of the components, including NP size and concentration and the molecular weight and concentration of polymers bound to the NPs. A comprehensive study of the dynamic mechanical character of 2-dimensional NP-surfactant assemblies showed that the dynamics of NP-polymer interactions are self-regulated across multiple time scales, and are associated with specific mesoscale interactions between self-similar and cross-complementary components. The mechanical properties of the NP-surfactant monolayer are tunable over a broad range, providing a control over the functional attributes of the to suit specific applications.