Naphthalimide‐Based Dyes as Photoinitiators under Visible Light Irradiation and their Applications: Photocomposite Synthesis, 3D printing and Polymerization in Water

Abstract

In this work, six new fluorescent dyes derived from the naphthalimide scaffold (Napht1–Napht6) were synthesized and used as high‐performance photoinitiating systems (PISs) in two and three‐component systems (combined with iodonium salt (Iod) and/or an electron donor amine (such as N‐phenylglycine[NPG])) for the radical photopolymerization of acrylate and methacrylate monomers under visible light using a light‐emitting diode at 405 nm. Markedly, these dyes were never synthesized before. In fact, these PISs showed high initiation efficiency with both demonstrating high final reactive function conversions and high polymerization rates. A further interest of our study is to determine the effect of the different substituents (chromophoric group) on the naphthalimide function, concerning the efficiency of initiation of the free radical polymerization. In order to improve the mechanical properties of the obtained polymers, these derivatives were also tested for the photopolymerization of a blend of acrylate/epoxy monomers (TA/EPOX); these latter properties were characterized by traction tests. To demonstrate the initiation efficiency of these dyes, several methods and characterization techniques were used, including steady state photolysis, real‐time Fourier transform infrared spectroscopy, emission spectroscopy as well as cyclic voltammetry. In our study, these naphthalimides were used for the synthesis of photocomposites (one and multiple layers of glass fibres) using a UV@395 nm (4 W/cm2) conveyor, as well as in the preparation of 3D printed polymers. Markedly, one of the naphthalimide derivatives (Napht‐4) can be used as a new high‐performance water soluble photoinitiator for photopolymerization in water and hydrogel synthesis.

Recent advances on coumarin-based photoinitiators of polymerization

“…Over the years, a wide range of structures have thus been examined for this purpose and naphthalimides, [23][24][25][26][27][28][29][30][31][32][33][34][35] squaraines, [36][37][38][39] iron complexes, [40][41][42][43][44][45][46] thioxanthones, [47][48][49][50][51][52][53][54][55][56] 2,3-diphenylquinoxaline derivatives, [57,58] iridium complexes, [59][60][61][62][63][64][65] perylenes, [66][67][68] chalcones, [69][70][71][72]…”

Recent advances on chalcone-based photoinitiators of polymerization

“…Considering the requirement for photoinitiators to strongly absorb in the visible range, a wide range of structures have been examined over the years, as exemplified with chromones, [26][27][28] benzophenones, [29][30][31][32][33][34] pyrenes, [35][36][37][38][39][40] diketopyrrolopyrroles, [41][42][43] coumarins, [44][45][46][47][48][49][50], iron complexes, [51][52][53][54][55][56][57] 2,3-diphenylquinoxaline derivatives, [58] naphthalimides, [59][60][61][62][63][64][65][66][67][68][69][70][71] squaraines, [72][73]…”

Naphthyl-Naphthalimides as High-Performance Visible Light Photoinitiators for 3D Printing and Photocomposites Synthesis

“…On the other hand, a JASCO FP-6200 spectrofluorimeter was used to determine the luminescence properties in solution, and their fluorescence quenching behavior. The electron transfer quantum yields (ϕ) for the PI quenched by Iod salt in chloroform could be calculated based to the classical Stern-Volmer treatment (I 0 /I = 1 + kq τ 0 [Iod]), where I 0 and I stand for the fluorescent intensity of Naphthalimide in the absence and the presence of Iod with the following equation: φ = (kq τ 0 [Iod])/(1+ kq τ 0 kq τ 0 [Iod]) [10]. τ 0 corresponds to the fluorescence lifetime determined using a time-correlated single-photon counting system (HORIBA ® Delta Flex with a HORIBA ® PPD-850 as detector; the excitation source is a HORIBA ® nano LED-370 with an excitation wavelength of 367 nm and a pulse duration inferior to 1.4 ns).…”

“…In fact, naphthalimide-based compounds have been used as photoinitiators for both FRP and CP [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. They are characterized by high molar extinction coefficients in the near UV and visible range, long excited state lifetimes and high fluorescence properties.…”