Kinetics of Cap Separation in Nitroxide-Regulated “Living” Free Radical Polymerization: Application of a Novel Methodology Involving a Prefluorescent Nitroxide Switch
Kinetics of Cap Separation in Nitroxide-Regulated “Living” Free Radical Polymerization: Application of a Novel Methodology Involving a Prefluorescent Nitroxide Switch
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硝基氧调节的“活性”自由基聚合中帽分离的动力学：涉及荧光前硝基氧开关的新方法的应用
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
J. Scaiano
中科院分区：
文献类型：
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作者：
Olga García Ballesteros;L. Maretti;and Roberto Sastre;J. Scaiano
采用预荧光顺磁传感器的新方法测定了由活性自由基聚合得到的tempo -cap聚苯乙烯的端裂绝对动力学。这种新方法利用了当这种发色团系在顺磁性氮氧化物上时香豆素荧光的抑制。香豆素-氮氧化物是一种极好的碳中心自由基陷阱；在自由基捕获后，产生的抗磁性烷氧胺具有强烈的荧光。因此，荧光积累是自由基形成的直接测量，可以用来量化它们的形成或研究它们的动力学。研究温度依赖性的过程可以用来确定活化参数和键离解能。这种简单的技术可以用来研究实际聚合物体系的动力学，克服了经常需要求助于模型化合物的问题。
A novel approach employing a prefluorescent paramagnetic sensor has been employed to determine the absolute kinetics for end-cap cleavage in TEMPO-capped polystyrene obtained by “living” free radical polymerization. This new methodology takes advantage of the suppression of coumarin fluorescence when this chromophore is tethered to a paramagnetic nitroxide. This coumarin−nitroxide is an excellent free radical trap for carbon-centered radicals; upon radical trapping, the resulting diamagnetic alkoxyamine is strongly fluorescent. Thus, fluorescence buildup is a direct measure of free radical formation and can be employed to quantify their formation or to study their kinetics. Studies of the temperature dependence of the process can be employed to determine activation parameters and bond dissociation energies. This simple technique can be employed to study the dynamics in the actual polymer systems, overcoming the frequent need to resort to model compounds.