A Water Soluble, Low Migration, and Visible Light Photoinitiator by Thioxanthone-Functionalization of Poly(ethylene glycol)-Containing Poly(beta-amino ester)

A novel photoinitiator (PI) is described here for low ecological impact, p(PEGDA575-TX): It is water soluble, polymerizable, thioxanthone (TX) functional, and is a one-component poly(ethylene glycol)-based poly(beta-amino ester). The PI is synthesized in one step via classical aza-Michael addition reaction between poly(ethylene glycol) diacrylate (M-n = 575 D) and amine functionalized TX (2-(2-aminoethoxy)-9H-thioxanthen-9-one). It absorbs at approximate to 404 nm (epsilon = 14 000-44 309) in water and can photodecompose with or without additives such as ethyl 4-(dimethylamino)benzoate (EDB) and bis-(4-tert-butylphenyl)-iodonium hexafluorophosphate (Iod). Although it is an effective one-component visible light PI for free radical polymerization of di- and tri(meth)acrylates, EDB or Iod will be favorable for synergistic effect. p(PEGDA575-TX) has higher initiating reactivity, reducing ability of oxygen inhibition and migration stability compared to TX, which make it environmental friendly.