Mechanically robust and self-healing waterborne polyurethane nanocomposites based on inorganic organic hybrid materials and reversible covalent interaction

Endowing waterborne polyurethane (WPU) materials with mechanically reinforced and self-healing property is a pressing issue for expanding practical applications. In this article, we proposed a simple method to give WPU with self-healing properties while improving the mechanical properties. First, furfuryl-modified silica nanoparticles (furan@SiO2) with high functionality and excellent dispersibility were prepared by the sol-gel method. Furan@SiO2 was then introduced into the side-hanging maleimide WPU to form a thermally reversible inorganic-organic network (WMSPUS-x) based on the Diels-Alder reaction. The morphologies and properties of furan@SiO2 and WMSPUS-x emulsions were analyzed by TEM and DLS, demonstrating the excellent dispersion of furan@SiO2 and the storage stability of emulsions. The cross-linking density of the nanocomposites was varied by the furan@SiO2 contents, and the effects of cross-linking density on mechanical and self-healing properties were systematically investigated. In addition, the thermal stability of WMSPUS-x nanocomposites was significantly improved shown by TGA results. Finally, qualitative and quantitative studies of the self-healing process were carried out to verify that WMSPUS-x nanocomposites possess great self-healing capacity. The outcomes indicate that WMSPUS-x nanocomposites have great potential for application as a smart material.