I would like to know the kind of UV lamp used in thiol-ene chemistry. Besides, is degassing crucial in this reaction? Has anyone worked with dopamine methacrylamide (DMA)?
I would suggest a Hg-lamp (around 250 nm). Degassing is necessary because of dissolved oxygen.
For most photoinitiators Hg lamps are the best choice. But there are also visible light photoinitiators, like camphorquinone or Irgacure 819 (phosphinoxide type) which can be used with dental lamps (violet LED or tungsten halogen lamp) which emit mainly in the region of 400nm. Degassing is advisable but the thiol-ene click chemistry is less sensitive to air than curing of acrylates without thiols. In thiol-ene click chemistry DMA is a chain stopper (it react with one mercapto group and results in a dead end). This must be considered in the recipe of the monomer mixture (more multifunctional monomers like pentaerythrit tetrakis mercaptopropionate or TMP-triacrylate). Furthermore DMA is by reason of the phenolic OH groups not a monomer without problems (the phenolic OH groups are inhibiters of radical reactions). But copolymers of DMA exists. Probably it is necessary to take a larger amount of photoinitiator as usual but 2 weight-% should be sufficient.
- Badges
- Science topic