Grafting Hyperbranched Polymers onto TiO2 Nanoparticles via Thiol-yne Click Chemistry and Its Effect on the Mechanical, Thermal and Surface Properties of Polyurethane Coating

In this study, we proposed a novel and facile method to modify the surface of TiO2 nanoparticles and investigated the influence of the surface-modified TiO2 nanoparticles as an additive in a polyurethane (PU) coating. The hyperbranched polymers (HBP) were grafted on the surface of TiO2 nanoparticles via the thiol-yne click chemistry to reduce the aggregation of nanoparticles and increase the interaction between TiO2 and polymer matrices. The grafting of HBP on the TiO2 nanoparticles surface was investigated by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) and thermogravimetry analysis (TGA). The thermal and mechanical properties of nanocomposite coatings containing various amounts of TiO2 nanoparticles were measured by dynamic mechanical thermal (DMTA) and tensile strength measurement. Moreover, the surface structure and properties of the newly prepared nanocomposite coatings were examined. The experimental results demonstrate that the incorporation of the surface-modified TiO2 nanoparticles can improve the mechanical and thermal properties of nanocomposite coatings. The results also reveal that the surface modification of TiO2 with the HBP chains improves the nanoparticle dispersion, and the coating surface shows a lotus leaf-like microstructure. Thus, the functional nanocomposite coatings exhibit superhydrophobic properties, good photocatalytic depollution performance, and high stripping resistance.