Synthesis of carboxyl cellulose nanocrystals/copper nanohybrids to endow waterborne polyurethane film with improved mechanical and antibacterial properties

The multifunctional nanohybrid fillers have attracted widespread attention in the field of polymer nanocomposites. In this study, carboxyl cellulose nanocrystals/copper nanoparticles (TCNC/Cu NP) nanohybrids were prepared by in situ growth of copper ions on the modified carboxyl CNC, and further doped into waterborne polyurethane (WPU)via solution blending. TEM, FTIR, XRD, and UV-vis analysis were used to characterize the morphology, composition, crystallization and structure of the as-prepared nanohybrid. TCNC/Cu NP nanohybrids exhibited good dispersion and interface compatibility in WPU matrix thanks to the modified CNC. The nanocomposite film obtained significantly enhanced mechanical, thermal stability and scratch resistance properties, which was attributed to a hydrogen bond network structure formed in the WPU matrix. Additionally, colony count method was performed to test antibacterial properties of various films. Compared to the pure WPU film, all of nanocomposite films showed good antibacterial properties against Escherichia coli and Staphylococcus aureus. The antibacterial ratio of the WPU nanocomposite film with the addition of TCNC/Cu NP (1:1) reach 99%. Furthermore, the results of a copper ion sustained release experiment showed that the nanocomposite film had a long-term release effect, which was ascribe to the strong bonding between TCNC/Cu NP nanohybrids and WPU matrix. Thus, Cu NP was firmly embedded in the hydrogen bonding network structure formed. This work gives a new approach to prepare the antibacterial WPU film with well mechanical properties.