A deep-curing UV-LED light photoinitiator based on diphenylpropanetrione

Benzophenone is a widely used type II photoinitiator, whose application is somewhat limited due to these shortcomings, such as short absorption wavelength, requirement for initiation with a co-initiator like tertiary amine and propensity to yellowing. In this study, 1,3-diphenylpropyltriacetone (DPPT) was synthesized and its photopolymerization was evaluated. Due to the adjacent conjugation of the tricarbonyl group, it has an absorption band at 400-500 nm. The photopolymeirzaition process of DPPT was tested by using real time FT-IR under 365 and 405 nm LED irradiation for various acrylate monomers. Interestingly, the results showed that the initiation efficiency of DPPT was improved by OH-containing monomers or alcohols. ESR-ST and steady-state photolysis experiments demonstrated that the benzoyl radicals were generated, but the photoreaction was expedited by the structure of the addition products of the central carbonyl group of DPPT and alcohol. Furthermore, the DPPT/alcohol initiator could be used for deep curing due to the light bleach property.