Abstract |
High-performance photoinitiators (PIs) are essential for ultraviolet-visible (UV-Vis) light emitting diode (LED) photopolymerization. In this study, a series of coumarin ketoxime esters (COXEs) with electron-donating substituents (tert-butyl, methoxy, dimethylamino and methylthio) were synthesized to study the structure/reactivity/efficiency relationships for substituents for the photoinitiation performance of PIs. The introduction of heteroatom electron-donating substituents leads to a redshift in the COXE absorption of more than 60 nm, which matches the UV-Vis LED emission spectra. The PIs also show acceptable thermal stability via differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The results from real-time Fourier transform infrared (RT-FTIR) measurements indicate that COXEs show an excellent photoinitiation efficiency for free radical polymerization under UV-Vis LED irradiation (365-450 nm); in particular, the conversion efficiency for tri-( propylene glycol) diacrylate (TPGDA) polymerization initiated by COXE-O and COXE-S (4.8 × 10-5 mol·g-1) in 3 s can reach more than 85% under UV-LED irradiation (365, 385 nm). Moreover, the photosensitization of COXEs in the iodonium hexafluorophosphate (Iod-PF6) and hexaarylbiimidazole/ N-phenylglycine (BCIM/NPG) systems was investigated via RT-FTIR. As a coinitiator, COXEs show excellent performance in dry film photoresist (DFR) photolithography. This excellent performance of COXEs demonstrates great potential for UV-curing and photoresist applications, providing a new idea for the design of PIs.
|
Authors | Shuheng Fan, Xun Sun, Xianglong He, Yulian Pang, Yangyang Xin, Yanhua Ding, Yingquan Zou |
Journal | Polymers
(Polymers (Basel))
Vol. 14
Issue 21
(Oct 28 2022)
ISSN: 2073-4360 [Electronic] Switzerland |
PMID | 36365582
(Publication Type: Journal Article)
|