Self-Assembly of Selected Sugar Surfactants in Choline Chloride-Urea Natural Deep Eutectic Solvent and Their Mixtures with Terpenoids

Natural deep eutectic solvents (NADES) represent a novel class of renewable and biodegradable solvents. We wish to investigate the self-aggregation behaviour of sugar surfactants (alkyl glucosides, sophorolipids, rhamnolipids) in NADES. More specifically, our solvent of choice is a 1:2 molar mixture of choline chloride and urea, named "reline". Fluorescence spectroscopy enabled us to characterise surfactants in reline. Interestingly, such solutions could solubilize monoterpenoids as limonene, menthol, borneol and pinene while changing the rheological properties dramatically. The unique combination of NADES, sugar surfactants and terpenoids results in a formulation of water-free biodegradable microemulsions. We see the possible application in cosmetics. With the help of small-angle neutron scattering, our objective is to shed light on the structure and size of these aggregates in NADES.