The carboxymethyl starch-based films in a presence of citric acid were prepared by casting technique. The influence of citric acid content on physicochemical properties of obtained hydrophilic films were evaluated (solubility in water, moisture absorption, mechanical and thermal properties). The crosslinking of starch derivative chains has been confirmed by FTIR spectroscopy, however, an excess of citric acid could cause hydrolysis of carboxymethyl starch chains. The best mechanical performance has been noted for the system containing 30 wt% (the highest tensile strength as well Young modulus 160 kPa and 650 kPa, respectively) as well as the highest T_g (ca. 58 °C). Additionally for the mentioned system the lowest solubility in water has been determined.

In this review, the application of deep eutectic solvents (DESs) as starch solvents, plasticizers and for other treatment has been described. Starch, as one of the most abundant biopolymers, is considered for forming new biodegradable materials. This new approach, referring to applying deep eutectic solvents for dissolving starch, its plasticization and other modifications, was presented. A DES could be a good alternative for common starch plasticizers (e.g., glycerol, urea) as well as recently considered ionic liquids. The high variety of DES component combinations makes it possible to obtain materials with the properties specific for given applications.