Synthesis And Application Of UV-curing Co-Synergists P-Dimethylaminobenzamides

In this paper three photo-initiator co-synergists were synthesized through a three-step process. They were 4-Dimethylamino-N,N-diethyl-benzamide, (4-Dimethylamino-phenyl)-piperidin-1-yl-methanone,(4-Dimethylamino-phenyl)-morpholin-4-yl-methanone.As a key step of the synthesis, the oxidation of p-dimethylamino-benzaldehyde was researched. Six different methods were studied here, and a new method has been find out which using Ag2O as catalysts and atmosphere as oxidant. The optimal operation variables were determined through orthogonal experiment: when Ag2O was 10% weight of the aldehyde and concentration of KOH was 3% at 60℃ for 24 h, the yield can be up to 75.8%.The three aromatic tertiary amines were added in acrylated epoxy prepolymer with photoinitiator ITX, and photoinitiability test shows the three amines display strong synergetic effect to the UV-curing system. Gel transform ratio test was used here for improving the traditional test methods, which made the curing process test quantificationally. Fluorescence emission spectra and UV absorb spectra analysis have been undertaken to test the influence of solvent polarity on the lowest excited singlet state of the tertiary amines. The absorption maxima were red-shafted slightly, and the emission maxima were red-shafted strongly, which showed all of the three compounds were found to be essentiallyππ* in character, which makes for the formation of triplet-exciplex state and the subsequent reactions,?known as photo-reduction and hydrogen-abstraction. The spectra data also showed the wavelength range of the aromatic amines' emission spectra in weaker polar condition was deeply overlapped with the wavelength range of thioxanthones' absorption spectra, which means aromatic amines can act as energy-transfer reagent in photo-initiation system with thioxanthone photo-initiator added in.The three products were tested by elementary analysis, Infrared spectrogram, Mass spectrogram, 1H nuclear magnetic resonance spectrogram and Ultraviolet spectrogram.