Synthesis and evaluations of cyclopolymerizable and cyclopolymeric type I photoinitiators

The aim of this thesis is to synthesize novel cyclopolymerizable and cyclic photoinitiators with high reactivity, water solubility, low migration and high thermal stability. In the first part of this work, two novel cyclopolymerizable Type I photoinitiators (DAA-I2959 and DAA-I184) were synthesized from reaction of diallyl amine (DAA) with tosyl ester of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959, I2959) in the presence of sodium hydroxide as catalyst or with acrylate ester of 1-hydroxycyclohexyl phenyl ketone (Irgacure 184, I184). A water soluble, linear polymeric photoinitiator (p-DADMAC-co-DAA-I2959-QS) was synthesized by thermal copolymerization of DAA-I2959 with diallyldimethylammonium chloride (DADMAC) in the presence of hydrochloric acid. This photoinitiator has five-membered cyclic units on the backbone and its Mn value was in the range of 40,000-60,000 D. DAA-I2959, its copolymer and DAA-I184 have strong absorbances at 272, 266 and 244 nm (extinction coefficient ~ 14705, 8000 and 11625), respectively, in methanol. In the second part of this work, reaction of DAA with tosylate ester of Irgacure 2959 was performed in the absence of a catalyst to give a mixture of two quaternary ammonium monomers, DAA-I2959-QS and DAA-Ts (tosylate salt of DAA). This photoinitiator has a strong absorbance at 269 nm (extinction coefficient ~ 15731) in methanol. The photoinitiating capabilities of the synthesized photoinitiators for the photopolymerization of poly(ethylene glycol) diacrylate (PEGDA, Mn = 575 D) or 2-hydroxyethyl methacrylate (HEMA) were investigated by differential scanning photo calorimetry (Photo-DSC) and compared with I2959 and I184. DAA-I2959, p-DADMAC-co-DAA-I2959-QS and DAA-I2959-QS/DAA-Ts exhibited fairly good migration stabilities (~ 3.5, 6.8 and 15.6 times higher) than that of I2959.