Understanding the thermoplasticization mechanism of polysaccharide at molecular level via computer simulations

Abstract

Polysaccharide like starch is the most promising green and sustainable packaging materials to replace fossil fuel based polymer. However, it is still a big challenge to directly make polysaccharide to be thermally plasticized due to its intense intra- and inter-molecular hydrogen bonds. In our previous studies, we have found that the addition of some specially designed chloride-contained organic compounds (named as supramolecular inducer) in thermal processing directly results in thermoplasticization of crop straw and corn starch like polysaccharides, yet the detailed thermoplasticization mechanism at molecular level is not fully understand. Herein, we extensively evaluate the potential thermoplasticization mechanism of polysaccharide thermally blended with different saccharide-based ionic liquid supramolecular inducers at molecular level via density functional theory and molecular dynamics simulations. Relevant results reveal that there are intense intra- (ca. 45.97 kcal mol−1) and inter-molecular (ca. 59.34 kcal mol−1) interactions in the neat polysaccharide macromolecules, leading to thermally unplasticizable of polysaccharide materials. Intense interactions between chloride atoms bonded on the supramolecular inducer and hydroxyl groups of polysaccharide macromolecules are observed, which are even stronger than these between chloride anions and hydroxyl groups of polysaccharides. Introduction of chloride atoms into supramolecular inducers is more facilitated to enhance the thermoplasticization of polysaccharide molecules in comparison with the chloride anions only supramolecular inducers. This investigation supplies an avenue to deeply understand the thermoplasticization mechanism of polysaccharide molecules, and is helpful to develop novel thermoplasticized polysaccharide packaging materials.