Université de Haute-Alsace, CNRS, IS2M UMR 7361, Mulhouse, F-68100, France.
Université de Strasbourg, France.
Macromol Rapid Commun. 2021 Aug;42(15):e2100207. doi: 10.1002/marc.202100207. Epub 2021 May 3.
A series of Type I photoinitiators (PIs) based on a nitrocarbazole scaffold are developed and examined for the first time as photoinitiators for visible light photopolymerization. Three oxime esters (OXE-M, OXE-V, OXE-P) varying by the terminal groups (acetyl, acryloyl and benzoyl) attached via the oxime ester group are originally prepared. As a result of this, the three PIs exhibit excellent photoinitiation abilities in the presence of acrylate monomers upon LED@ 405 nm irradiation. Markedly, OXE-M exhibits a better performance than the benchmark Type I phosphine-oxide (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide TPO). Chemical mechanisms supporting the polymerization process with these PIs are investigated by steady state photolysis, molecular orbital calculations and real-time Fourier transformed infrared spectroscopy. After the cleavage of N─O bond and decarboxylation, free radicals are generated to initiate the free radical polymerization efficiently. Free radical photopolymerization of OXE-M is applied in direct laser write and 3D printing. Interestingly, OXE-M exhibits thermal initiation behaviors in monomers and can be used as dual photo and thermal initiators. The highly opaque feature of carbon fibers makes it difficult for light penetration, so dual photo/thermal curing are used here to prepare carbon fiber composites.
首次开发了一系列基于硝基咔唑骨架的 I 型光引发剂 (PI)，并将其用作可见光光聚合的光引发剂进行了研究。三种肟酯 (OXE-M、OXE-V、OXE-P) 通过肟酯基团连接的末端基团 (乙酰基、丙烯酰基和苯甲酰基) 而最初被制备。结果表明，这三种 PI 在 405nm LED 照射下存在丙烯酸酯单体时具有优异的光引发能力。值得注意的是，OXE-M 的性能优于基准 I 型磷氧化物 (二苯基(2,4,6-三甲基苯甲酰基)氧化膦 TPO)。通过稳态光解、分子轨道计算和实时傅里叶变换红外光谱研究了这些 PI 聚合过程的化学机制。在 N─O 键断裂和脱羧后，生成自由基以有效地引发自由基聚合。OXE-M 的自由基光聚合被应用于直接激光写入和 3D 打印。有趣的是，OXE-M 在单体中表现出热引发行为，可用作双光和热引发剂。碳纤维的高不透明度使得光难以穿透，因此这里使用双光/热固化来制备碳纤维复合材料。
