Effect of Metal–Phenolic Quinone Network on the Performance of Thermomechanical Processed Chitosan-Silk Peptide Biomimetic Films: Improved Mechanical and Antibacterial Properties

This study investigates the effects of constructing a metal-phenol quinone network under thermomechanical processing on chitosan-silk peptide (CS-SP) composite films by varying tannic acid (TA) concentration and metal oxide types. The process was inspired by the hardening mechanism of insect cuticles. Upon TA addition, hydrogen bonding formed between TA and CS-SP, while covalent interactions occurred between oxidized quinone groups of TA and amino groups in CS-SP. Copper oxide and zinc oxide were found to promote quinone-mediated cross-linking. The mechanical properties of the composite films were significantly enhanced with TA addition, reaching a tensile strength of up to 43.5 MPa at 3% TA. The incorporation of copper oxide and zinc oxide further increased the tensile strength to 57.7 MPa and the hardness to 58.17 HD. Moreover, the combination of TA and metal oxides improved the antibacterial activity of the films against both <i>S. aureus</i> and <i>E. coli</i>. This work offers a scalable strategy for developing high-strength natural polymer-based composite films with promising applications in agricultural and food chemistry.