Low-Migration Monomeric Photoinitiators Based on 3-(Acryloyloxy)-2-hydroxypropyl Methacrylate

Three novel mono- and dimethacrylate-based functional photoinitiators (PIs) are synthesized from aza-Michael addition reaction of (i) amine derivative of 2-hydroxy-4 '-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) and 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) by controlling their stoichiometry (I2959-NH-AHM, I2959-N-2xAHM) and (ii) allyl amine derivative of I2959 and AHM (I2959-NA-AHM). Density functional theory is used to predict bond dissociation energies and the absorption maxima of the PIs. These PIs have similar lambda(max,) 272-280 nm, to I2959. The photocleavage mechanisms examined by electron spin resonance (ESR) indicate the formation of benzoyl and alkyl radicals. The homopolymerization reactivities of the PIs as monomers are found in the order of I2959-N-2xAHM > I2959-NH-AHM > I2959-NA-AHM. Their photoinitiating abilities of (meth)acrylate polymerizations studied using photo-DSC are similar to I2959. The migration of I2959-NA-AHM and I2959-N-2xAHM from the cured material is alleviated significantly compared to I2959. As a result, these PIs are promising candidates for the synthesis of environmentally friendly coatings.