Castor oil-based, robust, non-leaching and durable antibacterial waterborne polyurethane/polyhexamethylene guanidine composites prepared via an electrostatic self-assembly strategy

Antibacterial materials with durable antibacterial properties and high mechanical strength from renewable resources recently have attracted extensive attention. In this study, a facile and environmentally friendly electrostatic self-assembly strategy was adopted to prepare a series of castor oil-based waterborne polyurethane/ polyhexamethylene guanidine (WPU/PHMG) composites. The relationship between performance (antibacterial properties, mechanical properties, etc.) and the chemical structures of these resulting composite films has been systematically investigated. The results showed that the antibacterial rate of these antibacterial composite films against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was more than 99.9%. Interestingly, the obtained composite films still demonstrated long-lasting antibacterial properties after 42 days of immersion in water and six cycles of antibacterial testing due to the synergistic effect of electrostatic interaction and intermolecular hydrogen bonds. In addition, the tensile strength of the obtained composite films was significantly improved up to 30 MPa, 2 times higher than the original polyurethane films, and the toughness was high up to 70 MJ/m3, which could easily pull up to 19,000 times their own weight. Furthermore, the water absorption of the obtained composite films was greatly reduced from 56.4% to 6.6% due to their high crosslinking densities and intermolecular interaction. The technique reported in this study provides a facile and simple strategy for development of high mechanical properties and durable antibacterial properties of bio-based polymer composites, which would find promising applications in medical devices, product packaging, and so on.