Double noncovalent network chitosan/hyperbranched polyethylenimine/Fe 3+ films with high toughness and good antibacterial activity

The application of pure chitosan films is significantly limited due to their poor mechanical properties. In this study, a novel type of chitosan/hyperbranched polyethylenimine (CHP) and chitosan/hyperbranched polyethylenimine/Fe (CHPF) films with high toughness and good antibacterial activity were prepared through a noncovalent crosslinking method. From the tensile test results, the strain and toughness of the CHP film increased by 798.1% and 292.3%, respectively, compared with pure chitosan film, after the addition of 20% hyperbranched polyethylenimine (HPEI). The addition of trace metal iron ions (3 mg) forms a metal coordination bond with the amine group on HPEI, as well as the hydroxyl group and amine group on chitosan, and develops a double noncovalent bond network structure with hydrogen bonding, which further enhances the mechanical tensile strength of the chitosan-based film, with an increase of 48.4%. Interestingly, HPEI and Fe can be used as switches to increase and decrease the fluorescence property of chitosan, respectively. Furthermore, the CHP and CHPF films showed good antibacterial activity against and .