ESR and photopolymerization study of polymerizable benzophenone photoinitiators containing functional maleimide groups

Abstract

AbstractFour kinds of novel polymerizable benzophenone (BP) photoinitiators MBP, BMBP, MPBP, BMPBP containing functional maleimide groups, were used as free radical photoinitiators with N-methyldiethanolamine (MDEA) as coinitiator (H donor). Such photoredox systems were studied by means of ESR spectra. The results show that all the four photoinitiators possess the same initiation mechanism as BP/MDEA system; meanwhile, two kinds of radicals were observed as the excited triplet of the photoinitiators can abstract hydrogen from the methylene groups or the methyl groups of MDEA. The photopolymerization of three monomers with different functionality, methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA), initiated by these four polymerizable photoinitiators, was studied through dilatometer and photo- DSC. The results show that different photoinitiators behave differently towards monomers: MPBP system is the most efficient for all the three monomers; BMPBP is the least efficient for MMA, and BMBP is the least efficient for HDDA and TMPTA. The efficiency of the photopolymerization is greatly affected by maleimide groups and different vinyl monomers.