Low-migration, deep photocuring thiobarbituric acid-based one-component visible photoinitiators for high-efficiency photopolymerization

The practical applications of thiobarbiturates in medicinal chemistry exemplifies their exceptional biosafety, which is crucial for developing high -efficiency photopolymerization and low -migration photoinitiators (PIs). In this study, five novel D-pi-A visible PIs (ANs) were designed and synthesized via using aniline derivatives as the electron donor (D) and thiobarbituric acid as electron acceptor (A). EPR and steady-state photolysis display that the conjugated structure can be destroyed by intramolecular electron/proton transfer, leading to photobleaching. Real-time infrared (FT-IR) analyses have confirmed effective polymerization of 1,6-hexanediol diacrylate (HDDA) initiated by ANs and ANs/ N -methyldiethanolamine (MDEA) under illumination. The experimental molar extinction coefficient (epsilon) aligns with the oscillator strength ( f ) calculated via DFT, while the high epsilon and f of AN -5 facilitate electron transfer and free radical generation, resulting in improved initiation efficiency. The conversion rate of independent initiating polymerization exhibits an impressive 78 %. Moreover, colorless polymer columns initiated by AN -5 and AN-5/MDEA display curing depths of 45 mm and 50 mm, along with photobleaching rates reaching up to 98.7 % and 100 %, respectively. Especially, AN -5 exhibits the mere 0.2 % extraction rate from polymerization films under illumination (60 min). These results indicated the great potential of thiobarbituric acid -based ANs in deep -curing materials, food packaging.