ERC Grant SUPERFOAM

Foams are ubiquitous in our daily lives be it as milk foam on our cappuccino or as heat insulation of the building we live in.
The various important technological applications range from lightweight materials, waste water treatment to recycling of rare earth metals via ion flotation just to mention a few.
The vast number of possibilities to use foam in industrial processes and products originate from a unique tunability of optical, mechanical as well as chemical properties. This makes foams to an exciting object of current interdisciplinary research.

Although making aqueous foam is surprisingly easy as one “simply” has to lower the water’s surface tension by additions of surface active molecules, the foam is in most cases inherently unstable. Furthermore, foam formulation is usually performed purely empirically because the actual driving forces must be controlled on several length scales that reach down to the molecular level. For that reason understanding and controlling foam properties with a bottom-up approach is a major challenge in current research.

Structure-Property Relationship

Foams are hierarchical materials and as such they are greatly affected by the arrangement and distribution of gas bubbles on a macroscopic scale as well as on thickness and composition of lamella on a mesoscopic scale.
Although they are hidden in the bulk, liquid-gas interfaces are a building block of foams with overwhelming importance.
Thus composition, conformation and intermolecular interactions of a few molecular layers at liquid-gas interfaces – that are ubiquitous in aqueous foam – determine properties throughout the entire hierarchical chain.

Methodology of the SUPERFOAM project

In order, to put foam formulation and also our knowledge on foams on a molecular basis we need to characterize the latter in situ and on a molecular level. For that reason, our goal is to identify molecular building blocks which are comprised of solutes, ions and solvents at interfaces and their interactions that make the most stable foams or drive other foam properties. Once identified, we can use these building blocks to break the ground for new ways in foam formulation and related fields. Specifically, from this project we will get a library of structure-property relationships (SUPER) from which we can select molecular ingredients, tailor their interactions and thus generate FOAM based on molecular control.

Experimental Approach

The main focus of the ERC Starting Grant project SUPERFOAM will be on the molecular structure of interfaces and in situ charac-terization of interfaces. These experiments are a nucleation point for further studies on larger length scales - lamella, bubbles and macroscopic foam - which will be performed with solutions of identical composition. The approach will enable us to trace foam properties, bubble coalescence and lamella properties back to the actual molecular structures defining them. For that reason, we will divide the project into small work packages, which we can handle experimentally. At the conclusion of this project, we can unite the individual parts into a single concept on how molecular structures at gas-water interfaces should look like in order to make foam with the desired properties.

Interfaces

• Structure
• Composition
• Charging
• Adsorption kinetics of surface active molecules

Foam films and rising bubbles

• Composition
• Disjoining Pressure

Macroscopic Foam

• Bubble size distribution
• Stability & more