Push–pull biphenyl–based iodonium salts: Highly sensitive one-component photoinitiators for photopolymerization under UV–visible LEDs
Researchers found that newly synthesized biphenyl iodonium salts exhibit enhanced light absorption and can serve as highly efficient photoinitiators for UV-LED photopolymerizations.
Diaryliodonium salts play an important role as highly efficient photoinitiators in the field of photopolymerizations. They can rapidly photodecompose to produce free radicals and super acids; thus, can initiate highly efficient photocuring of acrylic and epoxy monomers and resins. However, the absorption of commercialized diphenyliodonium salts is poorly matched with popular LED light sources, and the participation of sensitizers is usually required to achieve efficient photoexcitation. Here, researchers synthesized five new phenyl biphenyl iodonium salts with different electron-pushing and electron-withdrawing substituents, e.g., methoxy and CN, at the biphenyl substituent.
Event Tip: High-performance Polyaryletherketone (PAEK) as an Alternative to PTFE
Polytetrafluoroethylene (PTFE) is widely used in kitchenware for its nonstick properties. However, with increasing concerns around PFAS-containing materials, alternatives are being explored. Polyaryletherketone (PAEK) is emerging as a promising new material. PAEK offers excellent thermal stability, chemical resistance, and mechanical properties, making it a strong alternative to traditional PTFE coatings. This webinar serves as a preview to the upcoming EC Conference, “Understanding PFAS and Reformulating PFAS-free Coatings”, and is free to attend. For a deeper dive into the PFAS issue, join us at the conference in Cologne, from November 18-19, 2024.
The results demonstrate that all synthesized iodonium salts have strong absorption in the range (λmax = 258–352 nm; εmax = 21,300–29,900 M−1 cm−1). The photochemistry of these synthesized iodonium salt is strongly influenced by substituents on the biphenyl ring. All iodonium salts can undergo rapid photolysis under light excitation, with higher quantum yield of photoacid generation reaching 0.25 and can quickly initiate cationic photopolymerization of epoxy monomers. Furthermore, free radicals are generated during photolysis, which can successfully trigger free radical polymerization. These iodonium salts with good absorbance in the UVA band demonstrate their potential as excellent photoinitiators under 365–405 nm LED excitation.
Source: Progress in Organic Coatings Volume 188, March 2024, 108209
