Novel irgacure 2959-based salts as photoinitiators for low migration products

The aim of this thesis is to improve the "green" aspects of photopolymerization processes. So novel photoinitiators with high reactivity, low migration, water solubility and biocompatibility are designed, synthesized and evaluated. In the first part of this work, a new cyclopolymerizable, doubly I2959 functionalized allyl-acrylate quaternary ammonium salt (2xI2959-QS) and its copolymer with diallyldimethylammonium chloride (DADMAC) were synthesized and their characterizations were done. Also, their photochemical properties, migration stabilities and photopolymerization behaviours were examined. The water soluble polymer, p-DADMAC-co-2xI2959-QS has five-membered pyrrolidine rings in the backbone and shows excellent thermal stability. These photoinitiators (PIs) have similar maximum UV absorption wavelength (271 and 272 nm in ethanol) to I2959, the molar absorption coefficient value of 2xI2959-QS is twice that of I2959. The photochemical mechanisms studied by electron spin resonance (ESR) and photolysis indicate formation of isopropyl ketyl radicals. Photopolymerization of 2-hydroxyethylmethacrylate (HEMA) initiated by both PIs shows higher efficiency than via I2959. The synthesized photoinitiators show higher migration stability compared to I2959 as reference. In the second part of this work, a new facile route to prepare highly water-soluble and migration stable photoinitiator was reported. A doubly Irgacure 2959 (I2959) functionalized meso-2,3-dimercaptosuccinic acid (DMSA) salt (DMSA-I2959-DBU) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) counterion was synthesized in one-pot thiol-Michael addition reaction. It has excellent water solubility (33 g/L), about 16 times higher than that of I2959. DMSA-I2959-DBU has similar maximum UV absorption wavelength value (272 nm in ethanol) but slightly lower molar absorption coefficient value (~11000) compared to I2959. Its decomposition mechanism was investigated by steady state photolysis. It shows reasonable photoinitiating reactivity towards (meth)acrylic double bonds.