A study of starch-urea-water mixtures with a combination of molecular dynamics simulation and traditional...

The relationships among the mixtures of starch, urea and water were intensively studied with a combination of molecular dynamics (MD) simulation and traditional characterization methods, including differential scanning calorimeter, scanning electron microscope, X-ray diffraction and Fourier-transform infrared spectroscopy, etc. In the presence of urea, the structure and morphology, as well as the thermal property of starch were significantly changed, which positively depends on the urea content in the aqueous solutions. In MD simulation, hydrogen bonds interaction as well as the distributions of starch fragments, urea and water in both molecular and atomic level were systematically studied. Hydroxyl oxygen atoms in glucose residue, nitrogen atoms in urea molecule and oxygen atom in water molecule are the main sites of the hydrogen bonding between the solute and solvent respectively. Conjunction of starch and urea becomes stronger than that of starch and water. In the course, the bulk water tetrahedral network is disturbed by urea, which has a significant influence on starch molecule movement.