1,2‐Diketones as photoinitiators of both cationic and free‐radical photopolymerization under UV (392 nm) or Blue (455 nm) LEDs

Abstract

The photoinitiation abilities of three 1,2‐diketones [i.e., acenaphthenequinone (ANPQ), aceanthrenequinone (AATQ), and 9,10‐phenanthrenequinone (PANQ)]‐based photoinitiating systems [PISs, with additives such as iodonium salt, N‐vinylcarbazole (NVK), tertiary amine, and phenacyl bromide (R‐Br)] for cationic photopolymerization and free‐radical photopolymerization under the irradiation of ultraviolet (UV; 392 nm) or blue (455 nm) light‐emitting diode (LED) bulb are investigated. All 1,2‐diketones studied exhibit ground state absorption that match with the emission spectra of UV (392 nm) or blue LED (455 nm) better than that of the well‐known blue‐light‐sensitive photoinitiator camphorquinone (CQ). In particular, AATQ/iodonium salt/NVK can show high photoinitiating ability (with epoxide conversion yield >70%) under the UV light irradiation due to the effect of NVK. In addition, 1,2‐diketone/iodonium salt (and optional NVK) systems are capable of initiating free‐radical photopolymerization of methacrylates, with conversions of 50–58%. Furthermore, some 1,2‐diketone/tertiary amine (and optional R‐Br) combinations are found to demonstrate high efficiency to initiate free‐radical photopolymerization, and 71% of methacrylate conversion can be achieved with PANQ/tertiary amine/R‐Br PIS. Some 1,2‐ketone‐based PISs can even exhibit higher efficiency than the CQ‐based systems. The photochemical mechanism of the radical generation from the 1,2‐diketone‐based PISs is investigated and found to be consistent with the related photopolymerization efficiency. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 792–802

New multifunctional benzophenone-based photoinitiators with high migration stability and their applications in 3D printing

“…This H-abstraction behavior was confirmed by ESR experiments. As shown in Figure 8, the hyperfine coupling constants of PBN radical adducts for BT3/EDB system are αN = 14.4 G and αH = 2.4 G, and it is in agreement with EDB(-H)˙ radical 29 . As a Type II photoinitiator, the interaction of BT3/EDB is depicted in r6.…”

Bis-chalcone derivatives derived from natural products as near-UV/visible light sensitive photoinitiators for 3D/4D printing

“…As shown in the Figure 9 (a) and (b), in the presence of Iod, the PBN/aryl radical adducts were clearly observed (aN = 14.4 G and aH = 2.2 G, in full agreement with literature data [51]) showing that r2 occurs. While for the bis-chalcone/amine system (Figure 9 (c) and (d)), the hyperfine coupling constants for nitrogen and hydrogen were characterized by aN = 14.4 G and aH = 2.2 G that evidenced the generation of an aminoalkyl radical (r3) according to experimental data published elsewhere (aN = 14.4 G and aH = 2.2 G, [52]).…”

Monocomponent Photoinitiators based on Benzophenone-Carbazole Structure for LED Photoinitiating Systems and Application on 3D Printing

“…The hyperfine coupling constants of PBN radical adducts for BPC1/EDB system are a N = 14.4 G and a H = 2.3 G ( Figure 8 b), and it is in agreement with EDB (−H) ˙ radical [ 39 ]. Under irradiation, BPC1 excited states interact with EDB.…”