Strengthening and Toughening Effects of Chitosan on the Bacterial Cellulose Films

Cellulose-based materials have been widely studied due to their biodegradability and excellent mechanical strength. However, the intrinsic brittleness of cellulose limits its applications. In this study, the bacterial cellulose-chitosan films were prepared by a casting method. The cellulose films with ≤ 30% chitosan exhibited a simultaneous increase in strength and toughness. The slippage of cellulose chains and dense network structure contribute to the improved strength and toughness of the cellulose-chitosan films. Besides, coarse-grained molecular dynamics simulations were performed to investigate the effects of different molecular factors (i.e., chain length, molecular interaction strength, and density) on the mechanical properties of cellulose-chitosan films. These molecular factors exhibited opposite effects on the tensile strength and strain at break. In particular, modifying the density of cellulose-chitosan films could simultaneously improve the strength and toughness significantly without sacrificing the elastic modulus. The findings provide physical insights into the strengthening and toughening effects of the cellulose-chitosan films.