Investigating Temporal Control in Photoinduced Atom Transfer Radical Polymerization
Investigating Temporal Control in Photoinduced Atom Transfer Radical Polymerization
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DOI：
10.1021/acs.macromol.0c00888
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发表时间：
2020-07-14
期刊：
影响因子：
5.5
通讯作者：
Matyjaszewski, Krzysztof
中科院分区：
文献类型：
--
作者：
Dadashi-Silab, Sajjad;Lee, In-Hwan;Matyjaszewski, Krzysztof
受控聚合的外部调节允许控制聚合的动力学并获得对聚合物生长的空间或时间控制。在光诱导原子转移自由基聚合（ATRP）中，光照射（再生）铜催化剂以启动聚合。然而，去除光不会立即使催化剂老化，聚合速率也不会变为零，因为链可能在黑暗中生长，因为残留的活化剂催化剂继续活化或铜催化剂在黑暗中再生。本文研究了聚合组分对光诱导ATRP的影响，以了解时间控制和光开关的相互作用。使用原位NMR以及在常规间歇条件下监测聚合动力学。在黑暗中聚合的程度取决于铜催化剂的活性，这是由配体和反应介质的性质调节。对于高活性催化剂，L/Cu-I活化剂的平衡浓度非常低，并且它被自由基终止反应迅速耗尽，产生与光的开关紧密匹配的时间控制。降低Cu催化剂的活性增加了活化剂的平衡浓度，导致在黑暗中显着的链增长。
External regulation of controlled polymerizations allows for controlling the kinetics of the polymerization and gaining spatial or temporal control over polymer growth. In photoinduced atom transfer radical polymerization (ATRP), light irradiation (re)generates the copper catalyst to switch the polymerization on. However, removing the light does not immediately inactivate the catalyst, nor does the rate of polymerization become zero as chains may grow in the dark because of continued activation by the residual activator catalyst or regeneration of the Cu catalyst in the dark. In this paper, the effect of polymerization components on photoinduced ATRP was investigated to understand the interplay of temporal control and light switching. Kinetics of polymerization were monitored using in situ NMR as well as under conventional batch conditions. The extent of the polymerization in the dark depended on the activity of the Cu catalyst, which was regulated by the nature of the ligand and reaction medium. For highly active catalysts, the equilibrium concentration of the L/Cu-I activator is very low, and it was rapidly depleted by radical termination reactions, yielding temporal control which closely matched the switching of light to on or off. Decreasing the activity of the Cu catalyst increased the equilibrium concentration of the activator, leading to significant chain growth in the dark.