A cyclopolymerizable, doubly Irgacure 2959 functionalized quaternary ammonium salt photoinitiator and its water-soluble copolymer with diallyldimethylammonium chloride

A new cyclopolymerizable, doubly 2-hydroxy-4 '-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959 or I2959) functionalized allyl-acrylate quaternary ammonium salt (2xI2959-QS) and its copolymer with diallyldimethylammonium chloride (DADMAC) are synthesized. The water-soluble polymer, p-DADMAC-co-2xI2959-QS, with M-n = 25 000 D has five-membered pyrrolidine rings in the backbone and shows excellent thermal stability. These photoinitiators (PIs) have similar values of lambda(max) (271 and 272 nm in ethanol) to I2959, and the epsilon value of 2xI2959-QS is twice that of I2959. The photochemical mechanisms studied using electron spin resonance (ESR) and steady-state photolysis indicate the formation of isopropyl ketyl radicals. Photopolymerization of 2-hydroxyethylmethacrylate (HEMA) initiated by both PIs shows higher efficiency than that via I2959. The synthesized photoinitiators show less migration ability (6% and 9% for 2xI2959-QS and p-DADMAC-co-2xI2959-QS) compared to I2959 (51%) as reference. Therefore, 2xI2959-QS and p-DADMAC-co-2xI2959-QS are promising PIs for the preparation of environmentally friendly coatings.