Water-soluble bis-chalcone-based photoinitiators with long-wavelength absorption for radical polymerization and 3D printing

Abstract

Two water-soluble bis-chalcone-based photoinitiators 4,4′-((((1E,1′E)-(2-oxocyclopentane-1,3-diylidene)bis(methaneylylidene))bis(thiophene-5,2-diyl))bis(9H-carbazole-3,9-diyl))bis(butane-1-sulfonic acid) (KSES) and 4,4′-((((1E,1′E)-(2-oxocyclohexane-1,3-diylidene)bis(methaneylylidene))bis(thiophene-5,2-diyl))bis(9H-carbazole-3,9-diyl))bis(butane-1-sulfonic acid) (KSTS) were successfully synthesized. The maximum absorption wavelengths (λ_max) of KSES and KSTS in water were 514 and 469 nm, respectively. KSES and KSTS could be combined with diphenyliodonium hexafluorophosphate (Iod) and triethanolamine (TEOA) to form a three-component photoinitiation system, which could quickly trigger the curing of acrylate coatings under visible light with a final CC bond conversion of more than 98%. The high free radical polymerization efficiency also made the bis-chalcone/Iod/TEOA system suitable for 3D printing, successfully printing clear and photobleached 3D objects. In addition, we carried out photosteady-state degradation, fluorescence quenching and ESR-ST experiments to further study the photopolymerization mechanism. Besides, KSES and KSTS also exhibited good biocompatibility, photobleaching performance and extremely low mobility. Considering the above excellent performance, the two water-soluble bis-chalcone-based photoinitiators reported in this study are very good choices for visible light polymerization in water-soluble systems.