Novel phenylamine‐based oxime ester photoinitiators for LED‐induced free radical, cationic, and hybrid polymerization

Abstract

Four new photoinitiators (PI's) containing various phenylamine-based groups as chromophores and oxime ester (OXE) as initiating groups are proposed for the free radical polymerization, the cationic polymerization, and interpenetrated polymer networks upon visible light exposure using a light emitting diodes at 405 nm. These compounds showed outstanding polymerization photoinitiation ability, that is, high-polymerization rates and good final reactive function conversions were obtained. The chemical mechanisms by which these OXE's generate reactive species were investigated through different techniques including real-time Fourier transform infrared spectroscopy, UVvisible spectroscopy, fluorescence (time-resolved or steady state) as well as cyclic voltammetry. Markedly, the proposed structures can be used as thermal initiators indicating all of them can be polymerized under suitable reaction temperature. In addition, due to their high efficiency, these optimized PI's were found to be useful @405 nm for both direct laser write and 3D printing applications.

Effect of the Steric Hindrance and Branched Substituents on Visible Phenylamine Oxime Ester Photoinitiators: Photopolymerization Kinetics Investigation through Photo‐DSC Experiments

“…Although the compounds of DMA – M , TP – 2P , TP – 2M and TP – 3M (Fig. 1) have been mentioned in our previous results (30), their photophysical, electrochemical and thermal properties were not present before. In addition, the new compounds of DMA – P , DEA – P (Fig.…”

“…The structures of oxime esters used in this work are shown in In addition, the structures are confirmed by mass spectra (Figures S5 and S6) and elemental analysis. Although the former four oxime esters have been published (30), the UV-vis, thermal properties, computation and photo-DSC results of all compounds have not been discussed in detail. Thus, the effect of the steric hindrance and branched substituents on phenylamine oxime esters is investigated.…”

“…The compounds of DMA – M, TP – 2P, TP – 2M and TP – 3M were synthesized according to our pervious report (30). In addition, the compounds of DMA – P and DEA – P were also prepared in the same manners.…”

“…In our studies on oxime esters for free radical photopolymerization, we had developed a series of phenylamine-based compounds with different substitution groups in its structures (29,30). The triphenylamine, alkyl chain and number of oxime esters in its structures indeed affect their electronic properties and photoreactivity.…”

“…The structures of DMA-M, TP-2P, TP-2M and TP-3M had been shown in our pervious report(30).All the synthetic procedures are including (a) formylation through an aromatic compound by Vilsmeier-Haack reaction; (b) oximation reaction through a carbonyl compound and hydroxylamine hydrochloride and (c) condensation reaction through a benzaldehyde oxime with benzoic anhydride in the presence of a base as a catalyst to afford the corresponding oxime ester photoinitiator. New compounds DMA-P and DEA-P are verified through 1 H NMR (Figures S1 and S2) and 13 C NMR (Figures S3 and S4) respectively.…”