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Issue 48, 2019
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Substituted stilbene-based oxime esters used as highly reactive wavelength-dependent photoinitiators for LED photopolymerization

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Abstract

Six novel oxime carboxylate photoinitiators were designed on the basis of a π-conjugated (E)-1-(4-styrylphenyl)-1-one subunit. Different substituent groups were introduced into three distinctive sites of the chromophore to rationalize their related electronic and structural effects on free-radical photoinitiating reactivities. The electronic properties, photodissociation mechanism, and structure–reactivity relationships were investigated by UV–visible spectroscopy, DFT calculations, real-time 1H NMR, electron spin resonance spectroscopy, and photo-DSC. We demonstrate that the structural change affecting the photoinitiating properties corresponds to a para-substitution effect on the stilbene subunit using an electron-acceptor group. Such a structural change leads to a 10-fold enhancement in initiation efficiency (Φi) upon visible irradiation of light-emitting diodes. The photoinitiating performances of these new derivatives are strikingly sensitive to the excitation wavelengths, leading to an impressive enhancement of Φi by more than three orders of magnitude from 365 nm to 405 nm irradiation. This wavelength-dependent reactivity previously observed for commercially available oxime esters can be generalized in our series and has high potential photocuring applications in low-power visible LEDs.

Graphical abstract: Substituted stilbene-based oxime esters used as highly reactive wavelength-dependent photoinitiators for LED photopolymerization

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Supplementary files

Article information


Submitted
04 Sep 2019
Accepted
12 Nov 2019
First published
12 Nov 2019

Polym. Chem., 2019,10, 6609-6621
Article type
Paper

Substituted stilbene-based oxime esters used as highly reactive wavelength-dependent photoinitiators for LED photopolymerization

S. Chen, M. Jin, J. Malval, J. Fu, F. Morlet-Savary, H. Pan and D. Wan, Polym. Chem., 2019, 10, 6609
DOI: 10.1039/C9PY01330J

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