Evaluation of Sulfonium Borate Initiators for Cationic Photopolymerization and Their Application in Hot Lithography AITranslate

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DOI：https://doi.org/10.1021/acsapm.3c00191

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Sulfonium hexafluorophosphates and perfluorinated tetraphenylborates are well established initiators in the field of cationic photopolymerization and have already been applied in 3D-printing at elevated temperatures, named hot lithography. The cyanide-ligated borane-based photoinitiator B2 shows lower molecular weight compared to state-of-the-art borates and is less expensive to synthesize from commercial starting materials. By comparing reactivity in the epoxy monomer BADGE, B2 outperforms commercial initiators in a broad range of temperatures with outstanding epoxy group conversions of up to 99%. Besides B2’s excellent performance as a cationic initiator, formulations containing B2 are thermally and storage stable and can be sensitized by anthracene derivatives. Hot lithography of B2 was carried out successfully at 90 °C and compared to existing sulfonium initiators. Layer quality and coloration of the fabricated and postcured parts are superior for B2. Overall, the cyanide-ligated sulfonium salt B2 represents an excellent initiator for cationic photopolymerization and application in hot lithography.