Four visible light triphenylamine-based oxime ester photoinitiators (TP-1–4) were synthesized and confirmed successfully through ¹H NMR, ¹³C NMR, and electron impact mass spectrometry (EI-MS) measurements as well as elementary analyses (EA). The design strategy for triphenylamine substituted photoinitiators involved the use of hydrogen atoms only for TP-1, one methoxy group for TP-2, two methoxy groups for TP-3 and two methyl groups for TP-4. The incorporation of triphenylamine derivatives in oxime esters gives near UV and visible light absorption characters with maximum absorption peaks at around 360 nm. Upon using a UV lamp as an irradiation source, all the oxime esters showed good double bond conversion efficiency in a range of 72–92% in the free radical polymerization of trimethylolpropane triacrylate (TMPTA) through photo-DSC experiments. Among all, TP-1 displayed the highest final conversion efficiency. Accordingly, the photochemical reaction behavior was studied using photolysis, cyclic voltammograms (CV), electron spin resonance (ESR) and theoretical calculations. Additionally, selected photoinitiating systems exhibited outstanding 3D patterns with high resolution and good edge definition through direct laser write (DLW) experiments @405 nm. This work thus demonstrates a judicious chemical design to fine-tune the photopolymerization character in triphenylamine oxime ester analogues.

中文翻译：

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三苯胺基肟酯光引发剂的合成及自由基光聚合

合成了四种可见光的基于三苯胺的肟酯光引发剂（TP-1–4），并通过¹ H NMR，¹³ C NMR和电子冲击质谱（EI-MS）测量以及元素分析（EA）成功进行了确认。为三苯基胺取代的光引发剂的设计策略只涉及了使用氢原子的TP-1 ，对于一个甲氧基TP-2 ，对于两个甲氧基TP-3和两个甲基基团为TP-4。在肟酯中掺入三苯胺衍生物可产生近紫外和可见光吸收特性，在360 nm附近具有最大吸收峰。使用紫外灯作为辐照源时，通过光DSC实验，在三羟甲基丙烷三丙烯酸酯（TMPTA）的自由基聚合中，所有肟酯在72–92％的范围内均显示出良好的双键转化效率。其中TP-1显示出最高的最终转化效率。因此，使用光解，循环伏安图（CV），电子自旋共振（ESR）和理论计算研究了光化学反应行为。此外，通过在405 nm处进行直接激光写入（DLW）实验，所选的光引发系统还具有出色的高分辨率和良好的边缘清晰度的3D模式。因此，这项工作证明了明智的化学设计，以微调三苯胺肟肟类似物的光聚合特性。