Synthesis and physicochemical characterization of novel biocompatible ionic liquids for the solubilization of biopolymers

During the last fifteen years, green chemistry became a central topic of academic and industrial research which is still progressively growing. In this context, many researchers are interested in alternative solvents which are environmentally friendly. Among them, there are ionic liquids (ILs) and deep eutectic solvents (DESs). The aim of the thesis was to development of new biocompatible ILs and DESs for the solubilization of biopolymers, such as cellulose. Short-chain two- and three-tailed quaternary alkylammonium (C3 - C6) associated with various biosourced carboxylates (e.g. itaconate, lactate, levulinate) have been good candidates and the identification of structural key factors for cellulose solubilization was realizable. This systematic approach coupled with extensive physicochemical study of ILs, resulted in the levulinates of [DiC3 ], [DiC4] and [TriC4] and [DiC4]itaconate as the most efficient with a solubilization of cellulose up to 10 %, or even 20 % in the presence of the bio-based co-solvent -valerolactone. Despite their good biodegradability in comparison with that of imidazolium, quaternary ammonium are not naturally resourced. They were therefore, in a second step, substituted by derivatives of choline, betaine and carnitine as biocompatible cations, associated with the above carboxylates. The ether- and ester-derivatives are ILs, and ethyl-choline ether levulinate is able to solubilize 10 % cellulose. Moreover, urea combined with dibutylammonium salts or betaine esters behave as DESs with melting temperatures around 30 to 40 °C. In the same way, DESs based on sugar-derivatives having an ether function on the anomeric carbon has been obtained in the presence of salts of choline, betaine and carnitine. Finally, a theoretical approach using the COSMO-RS software was used to model the properties of ILs and DESs and for predictions of cellulose solubilization