Abstract
Radical chemistry is a very convenient way to produce polymer materials. Here, an application of a particular photoinduced radical chemistry is illustrated. Seven new carbazole derivatives Cd1–Cd7 are incorporated and proposed as high performance near-UV photoinitiators for both the free radical polymerization (FRP) of (meth)acrylates and the cationic polymerization (CP) of epoxides utilizing Light Emitting Diodes LEDs @405 nm. Excellent polymerization-initiating abilities are found and high final reactive function conversions are obtained. Interestingly, these new derivatives display much better near-UV polymerization-initiating abilities compared to a reference UV absorbing carbazole (CARET 9H-carbazole-9-ethanol) demonstrating that the new substituents have good ability to red shift the absorption of the proposed photoinitiators. All the more strikingly, in combination with iodonium salt, Cd1–Cd7 are likewise preferred as cationic photoinitiators over the notable photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO) for mild irradiation conditions featuring their remarkable reactivity. In particular their utilization in the preparation of new cationic resins for LED projector 3D printing is envisioned. A full picture of the included photochemical mechanisms is given.
Highlights
IntroductionRadical (photo) chemistry plays a significant role in the production of polymer materials
Radical chemistry plays a significant role in the production of polymer materials
The ground of the new proposed in dichloromethane extinction coefficients in the near UV (e.g., Cd7 ~20,500 M−1·cm−1 @345 nm and 1500 M−1·cm−1 @405 (DCM) are shown in Figure 1
Summary
Radical (photo) chemistry plays a significant role in the production of polymer materials. Due to their advantages, compared to thermal activation and their applications as a green technology, light activated polymerization reactions are experiencing an ever increasing development and have inspired a lot of work on the design of photoinitiators PIs and multicomponent photoinitiating systems. PIs are able to produce radicals or cations under light exposure. Suitable PISs can have dual behavior: using the same system both a radical and a cationic. Suitable PISs can have dual behavior: using the same system both a radical and
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