Curing of DGEBA/ZnO nanocomposite with new fluorinated curing agents: Study of kinetics, water absorption, thermal and photophysical properties

In this study, two new fluorinated curing agents bearing imidazole-bisphenol and imidazole-diamine groups in their structures, namely: 4,4′-(2-(4-(trifluoromethyl)phenyl)-1H-imidazole-4,5-diyl)diphenol (TFIDO) and 4,4′-(4,4′-(2-(4-(trifluoromethyl)phenyl)-1H-imidazole-4,5-diyl)bis(4,1-phenylene)bis(oxy)bis (3-(trifluoromethyl)aniline) (TFIA) were synthesized, fully characterized and used to cure diglycidylether of bisphenol-A (DGEBA)-based epoxy resin and blend of DGEBA with nano ZnO (NZ) particles. Two mechanisms were anticipated to play roles in the curing reactions based on adducts formation and ionic complexes. The DGEBA/TFIDO system was more reactive than the DGEBA/TFIA system, whereas the thermal stability of DGEBA/TFIA was higher than that of DGEBA/TFIDO. These results can be explained by the increase in cross-linking density and more CF₃ groups in TFIA. The results indicated that cured materials showed red shift in absorption and fluorescence emission spectra and significant improvements in the water repellency and thermal stability. The NZ particles as catalyst increased the rate of cure reaction by decreasing the activation energy (E_a) and increasing the rate constant values.