Amine‑rich deep eutectic solvents for cassava thermoplastic starch: composition‑dependent structure–property mapping and aging resistance

Cassava‑based thermoplastic starch (TPS) is biodegradable yet constrained by brittleness, moisture sensitivity, and retrogradation. This study evaluates an amine‑rich deep eutectic solvent, choline chloride: monoethanolamine (ChCl: MEA, 1:2–1:5), as a dual plasticizer–compatibilizer for cassava TPS. Films (about 3 mm) were produced by twin‑screw extrusion and compression molding and benchmarked against glycerol‑plasticized TPS and a urea‑based DES (ChCl: urea, 1:2). ChCl: MEA markedly improved processability and properties: melt‑flow index increased from 1.02 to 2.36 g/10 min, glass‑transition temperature decreased from 72.4 to 36.8 °C, crystallinity index fell from 23.7% to 16.1%, thermal stability rose (286 °C to 320 °C), and water contact angle increased from 42° to 71.5°. The 1:3 composition achieved balanced mechanics (tensile strength 2.3 MPa; elongation 184%) and retained approximately 88% strength and approximately 81% elongation after 56 days at 23 °C/50% RH, outperforming glycerol (about 50% retention). All observed improvements were statistically significant (p < 0.05). Overall, the amine‑rich ChCl: MEA DES affords superior plasticization and aging resistance relative to glycerol and urea‑based DES, advancing cassava TPS toward robust, biodegradable packaging applications.