Non-toxic aryl diazirine photoinitiators

Photoinitiators offer an energy-saving alternative to thermal initiation, initiating free-radical polymerization through irradiation. Despite their benefits, current photoinitiators face issues of toxicity and solubility. Trifluoromethylphenyl diazirine, an aryl diazirine, is a promising photoinitiator that generates a carbene upon exposure to light. Aryl diazirines exhibit favorable optical and molecular properties, including minimal skin sensitization and liquid miscibility with aqueous and organic resins. Experimental studies demonstrate the ability of aryl diazirines to initiate free-radical polymerization of acrylate monomers, offering several advantages over traditional photoinitiators, such as TPO and BAPO. Aryl diazirines’ unique attributes include low cytotoxicity, prevention of resin shrinkage, and removal of unreacted monomers post-curing. R-group variants enable both UV and visible-light activation, thereby expanding their utility across biomedical and industrial sectors. The study explores the potential of aryl diazirines as photoinitiators for acrylate polymerization, addressing the limitations of current photoinitiators like toxicity and solubility. The authors hypothesize that aryl diazirines, with electron-withdrawing or alkyl para-substituents, can initiate radical polymerization effectively. They employ photorheometry to assess the polymerization process under various wavelengths and conditions, comparing results with commercial photoinitiators. The findings reveal that aryl diazirines achieve comparable mechanical properties to TPO, with advantages such as lower skin sensitization and better solubility in water-based resins. These properties make aryl diazirines promising for applications in biomedical fields and sustainable manufacturing. The study suggests future exploration of diazirines in 3D printing and bioadhesives, emphasizing their potential as non-toxic alternatives to traditional photoinitiators. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author. Aryl diazirines as a new class of photoinitiators. Irradiation of an aryl diazirine releases N2 and generates a triplet carbene that initiates free-radical polymerization of acrylate monomers through a hypothesized hydrogen abstraction mechanism. Unlike commercial photoinitiators, aryl diazirines exhibit unique benefits like being miscible liquids in both organic and aqueous environments, exhibit minimal cytotoxicity, and can absorb residual vinyl monomer through the diazoalkane isomer. The para-substituent tunes activation wavelength from 365 to 445 nm and nitrogen evolution offsets cure shrinkage.