Structural characterization and properties of deep eutectic solvents plasticized chitosan films

AbstractIn this study chitosan (CS) films were prepared from a deep eutectic solvent (DES) composed of choline chloride and malonic acid by solvent casting, and the influence of DES content on the structure and properties of the CS films was investigated in detail. It was confirmed by the spectral data that hydrogen bonds and ionic bonds were formed between the CS chains and DES. Structural analysis demonstrated that the crystallization of the CS was greatly hampered and the CS chains were stacked disorderly in films with high DES content. Differential scanning calorimetry (DSC) results indicated that DES exerted a significant plasticizing effect. In the case of the plasticized film containing 80 wt% of DES it showed a low glass transition temperature (Tg) of 20 °C. With increasing DES content, the water content of the plasticized films also increased, evidenced by the TGA results. Meanwhile, a structural change from granular to lamellar structure was observed by SEM. In addition, compared with pure CS film, the DES plasticized CS films possessed good fracture toughness and hydrophilicity. These observations suggest that the structure and properties of the CS films can be controlled by changing their DES content.Keywords: ChitosanDeep eutectic solventhydrogen bondsplasticizing effectmechanical propertiesDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. AcknowledgementsThis work was supported by the National Natural Science Foundation of China (No. 22178184).