Silver(I) complex with a Schiff base ligand extended waterborne polyurethane: A developed strategy to obtain a highly stable antibacterial dispersion impregnated with in situ formed silver nanoparticles

In this study, as a novel strategy to overcome gel formation and coagulation problem of waterborne polyurethane (WPU) dispersions containing silver ions, a Schiff base ligand (SBL) derived from 2,4-dihydroxybenzaldehyde and Bis(3-aminopropyl)amine was synthesized and utilized as chain extender in fabrication of WPUs. The effect of SBL incorporation into WPU chains and subsequent complex formation with Ag ions on the storage stability and particle size of the dispersions were studied. The UV-vis spectroscopy results of prepared dispersions confirmed the formation of Ag NPs within the WPUL/Ag sample through in situ reduction of Ag ions by PTMG (polytetramethylene glycol) polyol as a non-toxic reducing agent. Transmission electron microscopy (TEM) images of WPUL/Ag dispersion demonstrated that the formed Ag NPs exhibited a spherical shape with a size below 10 nm. Furthermore, X-ray diffraction (XRD) analysis of WPUL/Ag film affirmed the presence of Ag NPs within the WPUL matrix. Scanning electron microscopy (SEM) photographs of WPUL/Ag film also displayed a homogeneous dispersion for in situ formed Ag NPs. Antibacterial assays showed an excellent activity for WPUL/Ag film against S. aureus and P. aeruginosa bacteria. Besides, in vitro cytotoxicity studies confirmed that the WPUL/Ag sample possess a good biocompatibility toward L929 cells.