Copper (Photo)redox Catalyst for Radical Photopolymerization in Shadowed Areas and Access to Thick and Filled Samples
Copper (Photo)redox Catalyst for Radical Photopolymerization in Shadowed Areas and Access to Thick and Filled Samples
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DOI：
10.1021/acs.macromol.7b00622
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发表时间：
2017-05-23
期刊：
影响因子：
5.5
通讯作者：
Lalevee, J.
中科院分区：
文献类型：
--
作者：
Garra, P.;Dumur, F.;Lalevee, J.
以Cu（I）/碘鎓盐/锡（II）有机衍生物为光引发体系，在空气气氛下，在405 nm的LED光照射下，进行了低粘度甲基丙烯酸酯共混物的自由基聚合。该系统具有高反应活性，其中锡衍生物起着至关重要的作用。它通过催化循环运行，其中Cu（I）再生，并且可以在低浓度（0.1-0.3重量%）下使用。取得了令人瞩目的成绩。首先，对于35 mW/cm（2）的辐照度，在1.4 mm厚的样品中40 s后获得82%的最终甲基丙烯酸酯转化率，而仅当在200 mW/cm（2）的光暴露下使用Cu（I）/碘鎓盐体系时才达到这种转化率。第二，在非常低的辐照度（2.5mW/cm（2））下，150 s后仍然获得55%的转化率。第三，在阳光照射下产生在空气下几乎无粘性的厚样品（1.4mm）（对于1.4mm厚的样品，在照射90秒后转化率为65%）。第四，透明样品的光固化为9厘米（大概甚至更大），通过整个可聚合介质具有令人印象深刻的均匀性是可行的; 8.5厘米厚的填充样品的光聚合也被实现。第五，也是最后一个，横向聚合超出照射区域被证明与前所未有的延伸8毫米（锡（II）= 1.3%）和28毫米（锡（II）= 8%），这使得聚合反应发生在阴影区域。通过稳态光解和ESR自旋捕获实验研究了其化学机理。在聚合反应期间形成的氢过氧化物（ROOH）的后续作用是关键点，即对于阴影区域（厚的和填充的样品）中的聚合，这些潜在物质（ROOH）将由氧抑制产生，并且可以通过ROOH/Cu（I）氧化还原引发扩散以使样品完全固化。
The free radical polymerization of low viscosity methacrylate blends upon a LED irradiation at 405 nm under air is carried out using Cu(I)/iodonium salt/tin(II) organic derivative as photoinitiating systems. The system exhibits a high reactivity; where tin derivative plays a crucial role. It operates through a catalytic cycle in which Cu(I) is regenerated and can be used at low concentrations (0.1-0.3 wt %). Remarkable performances are achieved. At first, a final methacrylate conversion of 82% after 40 s in 1.4 mm thick samples is obtained for an irradiance of 35 mW/cm(2) whereas such a conversion is only reached only when using Cu(I)/iodonium salt system under a 200 mW/cm(2) light exposure. Second, a 55% conversion is still obtained after 150 s under a very low irradiance (2.5 mW/cm(2)). Third, almost tack-free thick samples (1.4 mm) under air are produced upon sunlight exposure (65% of conversion for the 1.4 mm thick sample after 90 s of irradiation). Fourth, the photocuring of clear samples as thick as 9 cm (and presumably even more) with an impressive homogeneity through the entire polymerizable medium is feasible; the photopolymerization of 8.5 cm thick filled samples is also realized. Fifth and last, a lateral polymerization beyond the irradiated area is demonstrated with unprecedented extensions of 8 mm (tin(II) = 1.3%) and 28 mm (tin(II) = 8%), which allows polymerization reactions to occur in shadowed areas. The Chemical mechanisms are studied by steady state photolysis and ESR-spin trapping experiments. The subsequent role of the hydroperoxides (ROOH) formed during the polymerization reaction is a key point i.e. for the polymerization in shadowed areas (thick and filled samples), these latent species (ROOH) will be generated from the oxygen inhibition and can diffuse for a full curing of the samples through a ROOH/Cu(I) redox initiation.