Novel monomeric and polymeric photoinitiators with type II and (Type I-or-H-donor) side chains

A recent trend in the effort to develop high performance photoinitiator (PI) systems for photopolymerization is to consider polymerizable or polymeric ones. These have some advantages such as high reactivity, low volatility and low migration in comparison with low-molecular weight nonmonomeric analogues. In this work, methacrylate monomers containing both Type I (Irgacure 2959) and Type II (benzophenone or thioxanthone) groups (PI1 and PI3) and both PI (benzophenone) and a coinitiator (sesamol) (PI2) in their structures were successfully synthesized. The copolymerizations of these monomeric photoinitiators with butyl methacrylate [PPI (BMA-co-PI1), PPI (BMA-co-PI2) and PPI (BMA-co-PI3)] were carried out to investigate the properties of polymeric photoinitiators. The photopolymerization efficiencies of the synthesized photoinitiators were investigated in the polymerizations of 1,6-hexanedioldiacrylate by real-time Fourier transformation infrared spectroscopy (FTIR) and compared with small molecule photoinitiators they are synthesized from (benzophenone, thioxanthone and Irgacure 2959). Broadband irradiation experiments for excitation of both chromophoric groups of PI1 and PI3 indicated no improvement on the efficiencies compared to their physical mixtures (BP/Irgacure 2959 and TX/Irgacure 2959). PI2-based one component PI systems were found to be an alternative to the use of conventional amine coinitiators.