Photografting of ZnO nanoparticles onto macromolecular chains via photolysis

Abstract

To investigate a novel method for ZnO nanoparticles (NPs) photoinitiators to better combine in photo-cured coatings, ZnO NPs were photo-grafted onto the macromolecular chains of the photo-curing films. The modified ZnO NPs (ZnO-TDI-1173 NPs) were prepared by the surface-reaction of ZnO NPs with 2-hydroxy-2-methylpropiophenone (Darocur 1173), which was confirmed by Fourier transform infrared spectroscopy, energy dispersive spectroscopy, scanning electron microscopy and X-ray diffraction, etc. Due to the relatively better hydrophobicity and compatibility of ZnO-TDI-1173 NPs in the photo-curable oligomer matrix than these of ZnO NPs, the fractured surface SEM images showed fewer agglomerates. As for the film properties of ZnO-TDI-1173 NPs/WPUA, the pencil hardness grade was H while that of pure WPUA was B; the value of gel ratio increased by 9.51% and the tensile strength (13.28±0.2 MPa) was about five times than that of pure WPUA (2.45±0.4 MPa). TGA data showed that the weight percentage of residuals at 600 °C was the highest among the four films. It implied that the covalent forces that ZnO-TDI-1173 NPs were in conjunction with WPUA matrix after photo-curing, and had relatively better thermal stability as well as mechanical properties in comparison to pure WPUA and ZnO NPs/WPUA films. Besides, the antibacterial investigation testified the antibacterial function of ZnO NPs/WPUA and ZnO-TDI-1173 NPs/WPUA. Therefore, ZnO-TDI-1173 NPs possessed a photo-grafting feature mechanism, with which functioned as both photoinitiators and nano-fillers. This paper demonstrated that the photolysis of ZnO-TDI-1173 NPs was a novel successful method to be grafted on the photo-cured films.