Deep eutectic solvents as simultaneous plasticizing and crosslinking agents for starch.

The aim of this work was to prepare deep eutectic solvents (DES) made with choline salts with α-hydroxylate anions and glycerol and apply them as starch plasticizers. Additionally, crosslinking potential of polyfunctional anions from the salts was investigated. Starch/DES premixtures were rheologically and thermally (DSC, TGA) analyzed. Thermoplastic starch (TPS)/DES films were prepared via thermocompression molding. Influence of choline salt to glycerol molar ratio, type of anion and compression parameters on mechanical, dynamic mechanical, thermal and sorption properties as well as structural morphology (XRD, FTIR analysis) was studied. DES containing citrate anion exhibited parallel crosslinking and plasticizing ability of polysaccharide matrix as applied techniques confirmed. The higher choline citrate (CCit) content in DES the higher tensile strength, more amorphous structure and lower sorption degree to CCit:G 1:6 M ratio. XRD revealed that TPS/CCit-based DES films did not retrograde even after one year of storage. The best compression parameters for studied systems were: 140 °C, 12 tons, 10 min.