Photocuring Kinetic Studies of TMPTMA Monomer by Type II Photoinitiators of Different Weight Ratios of 2-Chlorohexaaryl Biimidazole (o-Cl-HABI) and <i>N</i>-Phenylglycine (NPG)

Abstract

The curing behavior of the type II photoinitiator package based on different weight ratios of o-Cl-HABI (hydrogen acceptor)/NPG (hydrogen donor) systems (where o-Cl-HABI is a 2chlorohexaaryl biimidazole, NPG is an N-phenylglycine) was investigated through FT-IR, gel-fraction, electron spin resonance (ESR) and photoluminescence (PL) methodologies. As the amount of NPG increasing, the faster curing speed occurred. However, the curvature photo-reactivity phenomenon was observed as the amount of o-Cl-HABI at 0.5, 1 and 2 wt%, respectively. In addition, the radical transfer mechanism in the presence of air and nitrogen atmospheres was also discussed in this study.

Recent advances on visible light Triphenylamine-based photoinitiators of polymerization

“…Hexaarylbiimidazoles are also characterized by a low sensitivity to oxygen, which has stimulated the industrial interest for this family of structures. [288][289][290][291] To end, the high yield of lophyl radicals i.e. 2,4,5-triarylimidazolyl radicals make these structures appealing candidates to initiate the FRP of acrylates when combined to hydrogen donor (See Scheme 6).…”

“…As interesting feature, the carbon dioxide released during the decarboxylation reaction can also contribute to reduce the oxygen inhibition during FRP, CO2 impeding dioxygen to penetrate inside the resin. [290,314] Concerning triphenylamine-based oxime esters, four structures 35-38 were reported for the first time in 2021. [315] Here again, the substitution of triphenylamine by methoxy groups was examined (See Figure 32).…”

Recent Advances on Furan-Based Visible Light Photoinitiators of Polymerization

“…As a drawback, during the polymerization process, an irreversible consumption of the photoinitiator occurs. Conversely, Type II photoinitiators are bimolecular photoinitiators that can lead, in the presence of a hydrogen donor, to the formation of a ketyl radical and a second radical derived from the hydrogen donor molecule [92,97,[193][194][195][196][197][198]. In order to introduce the photosensitizer in a catalytic amount, a sacrificial amine is often used.…”

Recent Advances on Quinoxaline-Based Photoinitiators of Polymerization

“…A photoinduced electron transfer from the photosensitizer towards the onium salts is the key step to generating initiating radicals. However, Type II photoinitiators are also combined with hydrogen donors, leading to the formation of a ketyl radical with hydrogen abstraction and an additional radical issued from the hydrogen donor (See Scheme 1) [105,110,[169][170][171][172][173][174]. Considering that Type II photoinitiators are bimolecular photoinitiators, the introduction of a sacrificial amine can contribute to regenerating the photosensitizer in its initial redox state during the polymerization process so that this latter can be introduced in a catalytic amount.…”