New bimolecular photoinitiating systems based on terphenyl derivatives as highly efficient photosensitizers for 3D printing application†
New 2-(diethylamino)-4,6-diphenyl-benzene-1,3-dicarbonitrile derivatives were synthesized and proposed as high-performance photoinitiators in conjunction with iodonium salts for: (i) the cationic polymerization of epoxides, (ii) the free-radical polymerization of acrylates, and (iii) the synthesis of interpenetrating polymer networks (IPNs) from acrylate/epoxy blends. Investigated photoinitiating systems exhibit initiating efficiency upon exposure to soft irradiation conditions of visible light-emitting diodes (LEDs) with emission maxima at 405 nm and 420 nm. Excellent polymerization profiles are obtained during photopolymerization processes. The studied photoinitiating systems were also used for photosensitive resins for laser writing/3D printing experiments upon exposure to a laser diode at 405 nm. The photophysical and photochemical properties, i.e., absorption, steady-state photolysis and fluorescence spectroscopy, of terphenyl derivatives were studied. A photoinitiation mechanism related to the production of cations and radicals was studied using fluorescence quenching experiments, laser flash photolysis, cyclic voltammetry and electron spin resonance.