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

Abstract

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 λ_max (271 and 272 nm in ethanol) to I2959, and the ε 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.