Functionalisation of Natural Deep Eutectic Solvents (NADES) by Means of Self-Assembly

• Applicant: Professor Dr. Michael Gradzielski
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 498471922

Natural Deep Eutectic Solvents (NADES), due to their generally biofriendly character, are an interesting class of solvents that can be tuned largely with respect to their solvent properties by choice of their components. They can be made even more attractive for many potential applications by functionalisation via formation of self-assembled aggregates in them. By doing so one can control properties like solubilisation or rheological properties. However, so far NADES are often poorly characterised in physico-chemical terms and many of them suffer from high viscosity. Therefore, the first objective of this proposal is to change this by a thorough and systematic investigation of the phase behaviour of a large variety of NADES with a focus on developing low-viscous systems, as high viscosity is often preventing their practical application. For the most interesting NADES we will study for a range of (bio)surfactants, with different head groups micelle structure (mainly by light, x-ray, and neutron scattering) and thermodynamics of micelle formation (ITC, cmc), with the aim of identifying and quantifying solvophilic and solvophobic properties of the molecular motifs of the surfactants. For these surfactant systems we will also determine the solubilisation properties for typical oils and active agents, as this is typically a key aspect to employing surfactants. In a next step, self-assembly by amphiphilic copolymers is to be studied that leads to larger scale structuring. As polymer solubility in NADES is little known yet, first we will have to determine the solubility of different polymers to group them into soluble (A) and insoluble (B) homopolymers. Based on that knowledge amphiphilic block copolymers of AB and BAB type will be synthesized and their self-assembly properties in NADES will be studied, with a particular focus on the structures formed. The BAB-type copolymers should function as rheological modifiers for NADES and allow controlling their viscosity by self-assembly and network formation. The low viscous NADES employed for the self-assembly studies, will also become studied with respect to their nanostructure, in particular employing neutron diffraction experiments (this in close cooperation with the Australian partners), as depending on their composition, they may possess a more or less pronounced internal structure in the fluid state. A key objective of the project then will be to determine relations between the NADES fluid nanostructure and their ability to promote self-assembly, and how the structure of the self-assembled aggregates may be related to the nanostructure of the NADES. In summary, this project shall deliver the basic principles of self-assembly in different low viscous NADES, based on which tailored self-assembly in NADES for low and high Mw amphiphiles can be done, and which is adapted to the molecular structure of a given NADES.

• DFG Programme: Research Grants
• International Connection: Australia
• Cooperation Partners: Dr. Livia Salvati Manni; Professor Dr. Gregory Warr