Novel UV-curable epoxy resins modified with alkyne: Cured through thiol-yne click reaction

With the development of light-curing resin inks, various types of unsaturated resins modified with alkene have been reported in recent years. In this present work, however, the use of reactive monomers containing carbon‑carbon triple bonds to react with epoxy resin was proposed to synthesize unsaturated resins modified with alkyne, and then to explore the potential applicability of alkyne groups in photocurable resins. Therefore, propargylic acid and 2-butynoic acid were respectively used to introduce unsaturation by ring-opening reaction with epoxy groups, while the hydroxyl groups generated by previous reaction were used to introduce carboxyl groups by reaction with 1,2,5,6-tetrahydrophthalic anhydride to obtain the final alkyne-modified resins. Considering the highly efficient reactivity of thiol-yne click chemistry, the triple bond conversion of photocurable resins with and without thiol addition were prepared and compared to investigate the photosensitivity of them. It was found that resins modified with propargylic acid showed more photosensitivity and resins with thiol addition exhibited excellent triple bond conversion (the highest is nearly 100 %), meanwhile, in this study, thermal and dielectric properties of two alkyne-modified resins with different component additions were also tested and discussed.