Dual-function ChCl:MEA deep eutectic solvent for plasticization and compatibilization of starch–lignin blends: enhanced mechanical and thermal properties

Abstract

Abstract Starch–lignin (CS–Lig) blends commonly suffer from low ductility and poor interfacial compatibility, which limit their performance and processability. In this study, a choline chloride:monoethanolamine (ChCl:MEA, 1:3 molar ratio) deep eutectic solvent (DES) was investigated as a single dual-function additive for simultaneous plasticization of the starch-rich matrix and compatibilization of the starch–lignin interface, using glycerol as the reference plasticizer. Relative to glycerol, the DES system reduced mixing torque, melt temperature, and processing energy, indicating easier melt processing. It also produced a stronger depression of the glass-transition temperature, decreasing T g to 48.4 °C at the highest DES loading, and markedly increased elongation at break to 192.47 %. In addition, DES-plasticized blends showed a more homogeneous morphology, fewer interfacial defects, and higher onset thermal stability than the glycerol-plasticized counterpart (196.08 °C vs. 166.88 °C for the representative 2.0-part formulations). Overall, these results demonstrate that ChCl:MEA acts not only as an efficient plasticizer for the starch-rich matrix but also as an effective compatibilizer for the starch–lignin interface, providing a practical route to more processable and performance-balanced CS–Lig biocomposites.