Issue 8, 2020

Triphenylamine-hexaarylbiimidazole derivatives as hydrogen-acceptor photoinitiators for free radical photopolymerization under UV and LED light

Abstract

In this study, three triphenylamine-based hexaarylbiimidazole (HABI) derivatives featuring different numbers of methoxy groups (none for HABI1, two for HABI2, and four for HABI3) have been synthesized. For comparison, a common hydrogen acceptor photoinitiator, ocl-HABI (2-chlorohexaarylbiimidazole), was also applied to compare the corresponding properties. The new HABIs displayed a more red-shifted and higher molar extinction coefficient than ocl-HABI with the absorption region extended to visible light. A larger free radical concentration of HABIs was also achieved, which was confirmed via electron paramagnetic resonance (ESR) spectroscopy. These visible light-sensitive HABIs or ocl-HABI in combination with a suitable hydrogen donor, i.e., N-phenyl glycine (NPG) were utilized as photoinitation systems for conventional radical polymerization (RDRP). All the packages exhibited good electron-transfer ability by the calculation of the free energy changes (ΔGET). The HABI1/NPG system exhibited the best double bond conversion efficiency and outperformed the corresponding ocl-HABI/NPG-based formulation under similar UV light source testing conditions. We then employed the HABI1/NPG and ocl-HABI/NPG systems for LED light source testing. Again, HABI1/NPG had better photocuring conversion efficiency and shorter time at maximum heat flow than ocl-HABI/NPG, indicating that the HABI1/NPG system can be applied to light curing applications under different light sources, such as UV and LED.

Graphical abstract: Triphenylamine-hexaarylbiimidazole derivatives as hydrogen-acceptor photoinitiators for free radical photopolymerization under UV and LED light

Supplementary files

Article information

Article type
Paper
Submitted
24 okt 2019
Accepted
30 dec 2019
First published
02 jan 2020

Polym. Chem., 2020,11, 1504-1513

Triphenylamine-hexaarylbiimidazole derivatives as hydrogen-acceptor photoinitiators for free radical photopolymerization under UV and LED light

Y. Li and Y. Chen, Polym. Chem., 2020, 11, 1504 DOI: 10.1039/C9PY01605H

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