Regulating starch hydrogen bond network: ternary deep eutectic solvents induce performance enhancement and...

Under the global climate agreement, starch-based biodegradable materials offer a sustainable substitute for petroleum-based plastics. However, problems such as low solubility caused by their dense hydrogen bond network seriously restrict their processing and application. This study aimed to solve this bottleneck by mediating the starch hydrogen bond network through a multi-component deep eutectic solvent (DES). Combining experimental characterization and density functional theory (DFT), the mechanism of DES dynamically regulating the multi-scale reconstruction of starch was analyzed. The results showed that the ternary DES formed by B-U-G exhibited stronger hydrogen bonding (hydrogen bonding energy was -368.86 kJ/mol) and had more advantages in starch solubility. Tensile strength was enhanced by 29.56 % and elongation at break by 46.70 % in B-U-G-treated starch films versus native counterparts. In addition, the film contact angle test (31.72°) also decreased significantly. Despite unaltered A-type crystal structure, a 10.47 % crystallinity reduction, 40.29 % ΔH decrease, and reduced crystalline ordering were observed. Reduced density gradient (RDG) analysis revealed dynamic hydrogen bond formation between DES components and starch hydroxyl groups, inducing starch molecular chain disentanglement and reconstruction. This provided a theoretical mechanism for DES to regulate the hydrogen bond network of starch at multiple scales and offered ideas for the green modification of starch-based food packaging materials.