Novel polymeric photoinitiators comprising of side-chain benzophenone and coinitiator amine: Photochemical and photopolymerization behaviors

Three kinds of macrophotoinitiators, PBP-P, PBP-E and PBP-B, were synthesized by step-polymerization of benzophenone and different coinitiator amino monomers. The low molecular weight analogue, 2,4-di(3-(diethyl amino)-2-hydroxypropoxy)-benzophenone (DAHBP), was also synthesized as a low molecular weight model compound. The UV-vis spectra of PBP-P, PBP-E, PBP-B and DAHBP are similar with large red-shifted maximum absorption comparing with BP. ESR spectra of PBP-P and DAHBP possess the same initiation mechanism with DEBP/TEA systems. The photopolymerization of two monomers with different functionality poly(propylene glycol)diacrylate (PPGDA) and trimethylolpropane triacrylate (TMPTA), initiated by macrophotoinitiators and low molecular weight analogs, was studied through photo-DSC. The results show that different efficiency of photoinitiators towards monomers: first, polymeric photoinitiators are more efficient than low molecular weight analogs; then PBP-E is the most efficient for PPGDA; lastly, PBP-B is the most efficient for TMPTA. The efficiency of the photopolymerization is mainly affected by structure of amine in macrophotoinitiator.