Effect of starch-lipid complex on properties of starch-based materials: Mechanistic insights from molecular dynamics...

Starch exhibits limited mechanical flexibility and thermoplasticity due to the presence of disordered hydrogen bonds and chain entanglements, severely hindering its applications. This paper is based on the verified phenomenon that the formation of starch-lipid complexes can maintain the helical structure of starch. Molecular dynamics simulations were employed to investigate the complexation patterns between stearic acid and starch, as well as the evolution of chain conformations under multiple starch chains. Observations of morphological changes, along with variations in chain structural parameters, reveal the mechanism by which complexation reduces the conformational disorder of starch chains and further suppresses chain entanglements. The simulation results show that when the number of stearic acid chains is 5 times that of starch chains, the retention of the helical structure and mobility improvement of starch chains were the best. Subsequently, starch-based materials with varying degrees of complexation were prepared to validate the role of complex formation in maintaining the helical structure of starch chains. Additionally, the formation of the complexes was shown to enhance the mechanical flexibility and thermoplasticity of starch. Following the formation of well-defined complexes, the elongation at break of the starch-based materials exceeded 2000%. The viscosity at 50 °C and 100 rad/s was approximately only 3000 Pa·s.