Disubstituted Aminoanthraquinone-Based Photoinitiators for Free Radical Polymerization and Fast 3D Printing under Visible Light

The development of highly efficient and rapid photoinitiating systems for free radical photopolymerization under the irradiation of visible light has attracted increasing attention due to their widespread potential applications in, for example, 3D printing or dental polymers. Unfortunately, currently available visible-light-sensitive photoinitiators are not efficient enough for 3D printing applications suffering from low printing speeds. Here we describe a series of photoinitiating systems consisting of disubstituted aminoanthraquinone derivatives (i.e., 1-amino-4-hydroxyanthraquinone, 1,4-diaminoanthraquinone, and 1,5-diaminoanthraquinone) and various additives (e.g., tertiary amine and phenacyl bromide) toward the free radical photopolymerization of various acrylate monomers (such as commercial 3D resin) under the irradiation of blue to red LEDs. It is shown that the type and position of substituents of the aminoanthraquinone derivative can significantly affect its photoinitiation properties. The most efficient disubstituted aminoanthraquinone derivative-based photoinitiating system was selected and used for the 3D printing of a commercial 3D resin in a 3D printer with polychromatic visible light as the irradiation source. It is shown that its printing speed was dramatically enhanced compared to a commercial photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO).P.X. acknowledges funding from the Australian Research Council Future Fellowship (FT170100301). M.L.C. gratefully acknowledges support from the ARC Centre of Excellence for Electromaterials Science, a Georgina Sweet ARC Laureate Fellowship (FL170100041) and generous allocations of supercomputing time on the National Facility of the Australian National Computational Infrastructure. N.C. acknowledges funding from the Australian Research Council (FT140100834). EPR equipment is funded through the ARC LIEF program (LE170100023)