Molecular gels are materials that have been growing in popularity over the last twenty years. In addition to their potential applications in cosmetics, pharmacology, cell culture, and catalysis [1], their intrinsic physicochemical properties make them fascinating objects of study. The gelators used are low-molecular-weight molecules (less than 2000 gmol-1) capable of self-assembling via weak interactions to generate a fiber-like three-dimensional solid network, in which solvent molecules are trapped [1,2]. Changes to the chemical structure of gelators, as well as the nature of the solvent to be immobilized, can induce spectacular changes in the mechanical properties of the final gel. Thus, they are crucial parameters to consider during the various stages of the sequential self-assembly process, particularly during the first one: nucleation. These molecular gels can be viewed as crystallizations that have gone wrong. Instead of having well-defined crystals, crystallization occurs randomly throughout the volume of solvent. This raises the following question: What is the real impact of the chemical structure of gelling agents, and the resulting intermolecular interactions, on the macroscopic properties of the materials obtained?
In our group, we work on amphiphilic amino acid (leucine, phenylalanine, and lysine [3])-based gelators. Those molecules bear an alkyl chain of different length at the N-terminal extremity and a carboxylic acid or derivatives (ester, hydrazide…) at the C-terminal extremity. With these gelators, we can immobilise, among a wide range of various fluids, alkanes, DMSO/water mixtures, or oils. Using molecular analysis techniques, such as FT-IR and NMR, we examine the behaviour of gelling agents at the molecular level in different solvents.
[1] Raeburn J. Adams D., ChemComm. 51, 5170-5171 (2013).
[2] Collin D., Covis R. Allix F., Jamart-Gregroire B., Martinoty P., Soft Matter. 9, 2947-2958 (2013).
[3] Rangel Euzcateguy G., Parajua-Sejil C., Marchal P., Chapron D., Averlant-Petit M.-C., Stefan L., Pickaert G., Durand A., Polymer International, 70(3), 256-268 (2021)
