Multiscale analysis of the dynamic interactions of nanoparticles and oil-soluble surfactants at liquid interfaces

• Applicants: Professor Dr.-Ing. Lucio Colombi Ciacchi; Privatdozent Dr. Michael Maas
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Solid State and Surface Chemistry, Material Synthesis ; Synthesis and Properties of Functional Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450560405

Particle-stabilized emulsion systems see widespread industrial use in diverse areas, such as floatation in oil recovery or water remediation, in nutritional products, cosmetics and pharmaceutical formulations as well as in materials processing of composites and ceramics. In many of these applications the emulsion systems can be quite complex with various types of particles and surface-active molecules acting in synergy or competition to stabilize the droplet interface. Because of this complexity, the formulation of stable multi-component emulsion systems is usually still a resource-intensive trial and error process. Particularly, the packing density and percolation of mixed interfacial films can currently neither be controlled by adjusting established system parameters like concentrations, pH or surfactant types, nor are there adequate computational models that could support such a task.The aim of this project is to link the molecular details of heterogeneous and multi-component oil/water interfaces containing a mixture of both surfactant molecules and nanoparticles to the macroscopic behavior of these films. This requires a multiscale approach in which an adequate degree of complexity has to be carefully selected at every scale to reach a meaningful and efficient rational description and understanding of the system. From this understanding, we aim to generate design rules that allow us to tailor the formation of different types of particle/surfactant emulsion systems by acting on a few selected and easily accessible quantities and parameters, such as the oil/water surface tension and the macroscopic contact angle of an equivalent flat surface.To achieve this aim, we plan to access the same set of characteristic observables (in particular: contact angles, interfacial energies, adsorption energies, electron density profiles, interfacial microstructure and interfacial rheology) both from experiments and from atomistic and mesoscopic simulations. If the same values of observables are obtained from these complementary approaches, we can safely assume that the simulated models are a faithful representation of the experimental reality. In this way, we will have achieved a satisfying description of particle adsorption at the surfactant-laden interface and of structure formation in the particle film which determines the type of emulsion system.This combination of experimental and simulation methods will allow unprecedented insight into the formation of mixed interfacial films. With this approach we aim both to expand our knowledge on multicomponent interfacial systems on a fundamental level, as well as to enable the formation of complex emulsion systems based on predictable formulation rules. Such design rules will greatly facilitate the resource-intensive formulation processes which are necessary for a wide range of industrial processes from making ice cream to processing hierarchically structured porous ceramics.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Kurosch Rezwan