Mechanism of Cyclic Dye Regeneration During Eosin-Sensitized Photoinitiation in the Presence of Polymerization Inhibitors.
Mechanism of Cyclic Dye Regeneration During Eosin-Sensitized Photoinitiation in the Presence of Polymerization Inhibitors.
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DOI：
10.1002/pola.23649
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发表时间：
2009-10-07
影响因子：
--
通讯作者：
Bowman, Christopher N.
中科院分区：
文献类型：
--
作者：
Avens, Heather J.;Bowman, Christopher N.
发现可见光光引发剂伊红与叔胺共引发剂结合时，尽管存在至少1000倍过量的溶解氧，但仍能引发聚合，而溶解氧是自由基聚合的抑制剂。此外，0.4µM的伊红能够克服100倍过量的（40µM） 2,2,6,6-四甲基-1-胡椒酰氧基（TEMPO）抑制剂，仅在2分钟的抑制期后就开始聚合。相比之下，40µM Irgacure-2959，一个标准的裂解型引发剂，即使是等量的抑制剂（40µM TEMPO）也无法克服。通过对这两种引发体系的进一步比较，得出了与动力学数据一致的反应机理，并为伊红对氧、TEMPO和其他抑制剂相对不敏感提供了解释。提出了半还原的伊红自由基在抑制过程中与自由基抑制剂和自由基中间体发生歧化反应，使伊红再生并有效消耗抑制剂的循环机制。与伊红、玫瑰红、荧光素和核黄素的行为类似，尽管存在过量的TEMPO，但也发现了引发聚合的行为，这表明循环再生可能增强了许多染料光敏剂的光引发动力学。选择这样的染料引发系统构成了一个有价值的策略，以减轻自由基聚合的抑制作用。
A visible light photoinitiator, eosin, in combination with a tertiary amine coinitiator is found to initiate polymerization despite the presence of at least 1000-fold excess dissolved oxygen which functions as an inhibitor of radical polymerizations. Additionally, 0.4 µM eosin is able to overcome 100-fold excess (40 µM) 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) inhibitor, initiating polymerization after only a 2 minute inhibition period. In contrast, 40 µM Irgacure-2959, a standard cleavage-type initiator, is unable to overcome even an equivalent amount of inhibitor (40 µM TEMPO). Through additional comparisons of these two initiation systems, a reaction mechanism is developed which is consistent with the kinetic data and provides an explanation for eosin’s relative insensitivity to oxygen, TEMPO and other inhibitors. A cyclic mechanism is proposed in which semi-reduced eosin radicals react by disproportionation with radical inhibitors and radical intermediates in the inhibition process to regenerate eosin and effectively consume inhibitor. In behavior similar to that of eosin, rose bengal, fluorescein, and riboflavin are also found to initiate polymerization despite the presence of excess TEMPO, indicating that cyclic regeneration likely enhances the photoinitiation kinetics of many dye photosensitizers. Selection of such dye initiation systems constitutes a valuable strategy for alleviating inhibitory effects in radical polymerizations.
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影响因子：
6.2
作者：
Hansen, Ryan R.;Sikes, Hadley D.;Bowman, Christopher N.
通讯作者：
Bowman, Christopher N.
影响因子：
4
作者：
Blaya, S;Murciano, A;Fimia, A
通讯作者：
Fimia, A
影响因子：
--
作者：
O'Brien, AK;Cramer, NB;Bowman, CN
通讯作者：
Bowman, CN
影响因子：
5.5
作者：
DECKER, C;JENKINS, AD
通讯作者：
JENKINS, AD
影响因子：
5.5
作者：
Hawker, CJ;Barclay, GG;Devonport, W
通讯作者：
Devonport, W