Novel Copper Complexes as Visible Light Photoinitiators for the Synthesis of Interpenetrating Polymer Networks (IPNs)

Abstract

This work is devoted to the study of two copper complexes (Cu) bearing pyridine ligands, which were synthesized, evaluated and tested as new visible light photoinitiators for the free radical photopolymerization (FRP) of acrylates functional groups in thick and thin samples upon light-emitting diodes (LED) at 405 and 455 nm irradiation. These latter wavelengths are considered to be safe to produce polymer materials. The photoinitiation abilities of these organometallic compounds were evaluated in combination with an iodonium (Iod) salt and/or amine (e.g., N-phenylglycine—NPG). Interestingly, high final conversions and high polymerization rates were obtained for both compounds using two and three-component photoinitiating systems (Cu1 (or Cu2)/Iodonium salt (Iod) (0.1%/1% w/w) and Cu1 (or Cu2)/Iod/amine (0.1%/1%/1% w/w/w)). The new proposed copper complexes were also used for direct laser write experiments involving a laser diode at 405 nm, and for the photocomposite synthesis with glass fibers using a UV-conveyor at 395 nm. To explain the obtained polymerization results, different methods and characterization techniques were used: steady-state photolysis, real-time Fourier transform infrared spectroscopy (RT-FTIR), emission spectroscopy and cyclic voltammetry.

Recent Advances of Transition Metal Complexes for Photopolymerization and 3D Printing under Visible Light

“…Similar to Cu-3 (see Figure 7), the initiation of the photopolymerization was attributed to the formation of Ar• (Ar = 4-tert-butylphenyl) radicals from Iod by reaction with the Cu(I) complexes at the excited state. [95] Finally, only one example could be found for what concerns gold complexes. Herein, radical photopolymerization was initiated by low loadings (1.25 mol.% vs. coinitiator) of the binuclear Au(I) complex [Au 2 (𝜇-dppm) 2 ]Cl 2 (dppm = di(phenylphosphino)methane, Au-1) using EBPA as co-initiator and MMA as a monomer in solution.…”

“…Similar to Cu‐3 (see Figure 7), the initiation of the photopolymerization was attributed to the formation of Ar• (Ar = 4‐ tert ‐butylphenyl) radicals from Iod by reaction with the Cu(I) complexes at the excited state. [ 95 ]…”

Recent advances on carbazole-based oxime esters as photoinitiators of polymerization

“…[35] Face to these considerations, polymerization of thick samples and even of resins containing fillers can be achieved. Reprinted with permission from Bonardi et al [35] Considering that the light penetration is the key parameter for achieving high monomer conversions, a wide range of structures have been examined ranging from truxene derivatives [36] to copper complexes, [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] carbazoles, [54][55][56][57][58][59][60][61][62][63][64][65] chalcones, [28,[66][67][68][69][70][71][72][73][74][75][76][77][78] zinc complexes, [79] acridones,…”