Nucleation of separating liquid phases in elastic polymer networks

• Applicant: Dr. Charlotta Lorenz
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Experimental Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 523842861

In this project, I aim to create a new generation of bio-inspired materials based on elastically-arrested phase separation. Arrested phase separation is a key mechanism also used by living systems to create well-controlled nanostructures. One of the most salient example is structural color as present in some bird and insect species. Next to fascinating optical properties, phase-separating composite systems can have astonishing mechanical properties: For example, liquid inclusions can stiffen soft polymer networks although a higher liquid fraction would be expected to soften a network. These mechanical properties have been less studied compared to the optical properties. So far, liquid-liquid phase separation in polymer networks is not fully understood from its nucleation on. However, this understanding will significantly contribute to make resulting optical and mechanical properties controllable. Thus, with my project, I aim to understand and control nucleation in liquid-liquid phase separation in polymer networks: 1. I will investigate the nucleation process and the influence of the polymer network on nucleation and growth of the nucleating droplet from the nm- to μm-scale. For example, such parameters as the mesh size and the crosslinking density of the network are likely to influence droplet nucleation. These measurements will reveal an energy landscape of nucleating droplets and factors which allow changes of this energy landscape. 2. By varying the parameters determining nucleation, I aim to control phase separation in liquid-liquid phase separating systems. 3. Variation of these parameters will lead to control of the mechanical properties of the studied samples. These studies can result in highly flexible, self-assembled materials, which are comparatively fast and easy to produce. My findings will contribute to the field of self-assembled structures and liquid-liquid phase separation. I will unravel the influence of polymer networks on the phase separation kinetics of liquids. These results might find application in fabrication of colors, porous materials and fabric production. My project will result in new functional materials which can be, for example, simultaneously soft and tough.

• DFG Programme: WBP Fellowship
• International Connection: Switzerland
• Host: Professor Eric R. Dufresne