Allyloxy ketones as efficient photoinitiators with high migration stability in free radical polymerization and 3D printing

Abstract

Five ketone derivatives(ketone-1~ketone-5) never synthesized in the literature and containing the same peripheral 1,3-bis(allyloxy)benzene substitutinggroup but different central cyclohexanone cores were designed and proposed as high-performance photoinitiators for the free radical polymerizationof acrylates under mild conditions. In combination with an amine and an iodoniumsalt(Iod), these ketones could initiate the photopolymerization of di(trimethylolpropane) tetraacrylate(TA), a tetrafunctional acrylatesmonomer, upon visible LED irradiation at room temperature in both thick films (1.4 mm) and thin films (25 μm) conditions. The distinct photopolymerization profiles of acrylateswere studied byreal time Fourier transform infrared spectroscopy, which indicated that the ketone-2/amine/Iod system could induce the highest final conversion of acrylatesin thick films condition, while ketone-5/amine/Iod system could induce the highest final conversion of acrylatesin thin films condition. Photoreactivity of ketone-2 and ketone-5 wassystematically investigated bysteady state photolysis and fluorescence quenchingexperiments in the presenceof an amine and an iodonium salt, respectively.Moreover,eminentmigration stabilityof ketones in photocured TA was observed. Finally,the ketone-2 and ketone-5-based three-component photoinitiating systems were applied forthe laser writing experiments of TA, and macroscopically tridimensional patterns were fabricatedwith an excellent spatial resolution.