PHOTOCHEMISTRY AND PHOTOPOLYMERIZATION ACTIVITY OF NOVEL 4-ALKYLAMINO BENZOPHENONE INITIATORS SYNTHESIS, CHARACTERIZATION, SPECTROSCOPIC AND PHOTOPOLYMERIZATION ACTIVITY

Fifteen novel 4-substituted alkylaminobenzophenones have been synthesized and characterized using NMR, mass spectrometry and microanalysis. Their spectroscopic properties have been determined using u.v. absorption and phosphorescence analysis and the data related to their behaviour on photocuring using both Fourier Transform Infra-Red (FTIR) analysis and hardness testing in a triacrylate monomer. Absorption and phosphorescence spectra are similar to those of benzophenone although the quantum yields are lower with longer emission lifetimes indicative of the presence of some degree of charge-transfer in the lowest excited triplet state. Using FTIR analysis for photocuring, the compounds are in many cases more effective than benzophenone itself. Using hardness testing on the other hand, all the compounds proved to be more effective; the alicyclic amine structures are the least effective followed by the aliphatic and then the aromatic amines. For structural analogues, photocuring was more effective for those containing a propoxy link in the substituent than for those containing an ethoxy link. This difference is related to the ability of the molecule in the former case to form an intra-molecular exciplex with the aromatic ketone group. The alicyclic compounds are less effective in hydrogen atom or electron abstraction reactions. Differences observed in the methods of curing are related to the quenching effects of oxygen. © 1990.