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 substituting group but different central cyclohexanone cores were designed and proposed as highperformance photoinitiators for the free radical polymerization of acrylates under mild conditions. In combination with an amine and an iodonium salt (Iod), these ketones could initiate the photopolymerization of di(trimethylolpropane) tetraacrylate (TA), a tetrafunctional acrylates monomer, 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 acrylates were studied by real time Fourier transform infrared spectroscopy, which indicated that the ketone-2/amine/Iod system could induce the highest final conversion of acrylates in thick films condition, while ketone-5/amine/Iod system could induce the highest final conversion of acrylates in thin films condition. Photoreactivity of ketone-2 and ketone-5 was systematically investigated by steady state photolysis and fluorescence quenching experiments in the presence of an amine and an iodonium salt, respectively. Moreover, eminent migration stability of ketones in photocured TA was observed. Finally, the ketone-2 and ketone-5-based three-component photoinitiating systems were applied for the laser writing experiments of TA, and macroscopically tridimensional patterns were fabricated with an excellent spatial resolution.

Substituent effects on the photoinitiation ability of coumarin-based oxime-ester photoinitiators for free radical photopolymerization

“…For direct laser write experiments, a laser diode @405 nm (spot size around 50 μm) was used for the spatially controlled irradiation. The photosensitive resin was polymerized under air and the generated 3D patterns were analyzed using a numerical optical microscope (DSX-HRSU from Olympus Corporation) as presented in the references [24][25][26][27][28] .…”

“…OXEs have been reported to undergo photoinduced decarboxylation in high quantum yields. [28][29] Remarkably, as we can see from Table 3, we can notice that the decarboxylation reaction is energetically the most favorable in the case of OXE-D (Hdecarboxylation = E(R•) + E(CO2) -E(RC(=O)O•) = -4.94 kcal.mol -1 -Table 3), the generated CO2 was detected by real time Fourier transformed infrared spectroscopy (RT-FTIR) and the infrared spectra of OXE-D at t = 0 s and t = 30 s are presented in Figure 4(B). For the other OXEs, this peak is not observed suggesting a low decarboxylation yield in agreement with an unfavorable process (Hdecarboxylation > 0; Table 3).…”

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 in bis-Chalcone-Based Photoinitiators of Polymerization: From Mechanistic Investigations to Applications

“…The extractability and migratability of photoinitiators is a major issue that can drastically affect future uses of polymers. In this context, in order to reduce the extractability of dyes, polymerizable groups can be introduced, as exemplified with C32-C36; for comparison, C14 [113], previously studied, was used as a non-crosslinkable chalcone (see Figure 16) [110]. The comparison between the crosslinkable chalcone C36 and its non-crosslinkable version C14 revealed the remarkable migration stability of C36 compared to C14.…”