Deep Eutectic Solvent as Dual Solvent–Catalyst for Efficient Starch Esterification With Vinyl Laurate via Reactive Extrusion

Fatty starch esters have attracted increasing interest as sustainable polymers due to their processing versatility and wide range of applications in biobased and biodegradable materials. However, conventional esterification methods often require highly polar organic solvents, operate under low starch concentrations, and require extended reaction times. We have developed a green approach to esterify wheat starch by reactive extrusion using a novel deep eutectic solvent (DES) based on a mixture of benzyltriethylammonium chloride (BTEAC) and imidazole (IM). This DES acted both as a starch solvent and as an activating agent for vinyl laurate (VL) via the in situ formation of a highly reactive lauryl imidazolide species. The esterification was completed within 15-30 min depending on the reaction temperature. The modification of starch over a broad range of VL/glucose unit molar ratios (0.5 to 2.5) was confirmed using infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy analyses that revealed the role of IM in the esterification process, allowing us to detail the reaction pathway. This novel modification approach has not been reported so far and opens new opportunities for the development and upscaling of biobased polymers based on esterified starch, with promising applications in sustainable packaging.