Preparation of a new BTEAB/DMSO deep eutectic solvent for highly efficient starch dissolution and succinylation

In this work, a novel deep eutectic solvents (DES) based on benzyltriethylammonium bromide/dimethyl sulfoxide (BTEAB/DMSO) is prepared and described. Comprehensive physicochemical analyses revealed a eutectic point at 0 °C, demonstrating the formation of a highly stable liquid phase characterized by strong intermolecular interactions between the two components. Beyond its original preparation, this DES proved to be an exceptionally efficient medium for biomass processing. It enabled the dissolution of up to 22 wt% of starch at 90-95 °C, a value significantly higher than typically achieved with other solvents. Moreover, the BTEAB/DMSO system served as a reactive medium, enabling direct esterification of starch with succinic anhydride under catalyst-free conditions, thereby simplifying the process and making it more environmentally sustainable. A full suite of structural, morphological, and thermal characterizations, including FTIR-ATR, H¹ NMR, XRD, SEM, EDX, and TGA, confirmed substantial modification of starch after treatment. The regenerated material exhibited a marked loss of crystallinity, the disappearance of native granules, changes in elemental composition, and a decrease in thermal stability, all of which are consistent with successful incorporation of succinyl groups. These results clearly demonstrate that the BTEAB/DMSO DES is not only a powerful solvent but also an effective reaction platform for starch valorization. Overall, this study introduces a highly promising, eco-friendly strategy for polysaccharide processing and opens new avenues for sustainable chemical transformations based on DES.