Scrutiny of the supramolecular structure of bio-sourced fructose/glycerol/water ternary mixtures: Towards green low transition temperature mixtures

Abstract

This work deals with fully green ternary mixtures composed of three low cost, bio-sourced and safe molecules, namely Fructose (F), Glycerol (G), and Water (W), able to interact to each other by H-bonds. Through an eco-friendly approach, we prepared a series of FGW mixtures differing in their composition in order to identify the combinations exhibiting a long-lasting macroscopic homogeneity. To well understand how water interferes in such as mixtures, we focused on thermal transitions, changes in viscosity and activation energies, and on internal organization at the molecular scale through NOESY and PFG-NMR experiments. It resulted that, as a function of the water content, the FGW mixtures can be defined either i) as a cooperatively H-bonded supramolecular structure in which water is actively involved in the interactions, thus leading to stable solvents designed as low transition temperature mixtures (LTTM), or ii) as aqueous solutions due to the diluting effect of water which disrupts the H-bonded organization and promotes the overall mobility. This comprehensive study is a prerequisite for a further industrial implementation of such eco-designed solvents in various applicative attractive domains, as in cosmetic field.