Abstract: The synergistic effects of combination photoinitiation system composed of 2,2-alkyl-2-alkylaminoacetophenone (α-AK) and diarylketone (BP, MK, EAQ and TX) were studied. Addition of diarylketone to α-AK significantly improved the absorption at long wavelength near UV region. Effects of different diarylketones on photopolymerization were compared. Among these, CTX and BP are superior to other compounds and give an increase of polymerization rate by a factor of 1.3-1.5, whereas MK and EAQ have no distinct influence. Effects of solvent polarity and concentration were also studied. The results indicate that the increase of solvent polarity has a negative effect, the excellent effect is approached when α-AK and DAK are equimolar, and the reactivity of chlorothioxanthones (CTX) is higher than that of other alkylthioxanthones (ITX, DETX). The mechanism of synergistic effects of α-alkylaminoacetophenone and diarylketone was investigated by absorption spectra and the results demonstrate that the two different mechanisms, triplet energy transfer sensitization and photoreduced reaction, exist and their attributions depend on the different diarylketones.

Key words: 2,2-dialkyl-2-alkylaminoacetophenone/diarylketone combination, photoinitiation polymerization, synergistic effect