Probing the Reactivity of Photoinitiators for Free Radical Polymerization: Time-Resolved Infrared Spectroscopic Study of Benzoyl Radicals
作者:Christopher S. Colley、David C. Grills、Nicholas A. Besley、Steffen Jockusch、Pavel Matousek、Anthony W. Parker、Michael Towrie、Nicholas J. Turro、Peter M. W. Gill、Michael W. George
DOI:10.1021/ja026099m
日期:2002.12.1
of substituted benzoyl radicals has been generated by laser flash photolysis of alpha-hydroxy ketones, alpha-amino ketones, and acyl and bis(acyl)phosphine oxides, all of which are used commercially as photoinitiators in free radical polymerizations. The benzoyl radicals have been studied by fast time-resolved infrared spectroscopy. The absolute rate constants for their reaction with n-butylacrylate
通过 α-羟基酮、α-氨基酮以及酰基和双(酰基)氧化膦的激光闪光光解产生了一系列取代的苯甲酰基自由基,所有这些都在商业上用作自由基聚合中的光引发剂。苯甲酰基自由基已通过快速时间分辨红外光谱进行了研究。在乙腈溶液中测量它们与丙烯酸正丁酯、苯硫酚、溴三氯甲烷和氧气反应的绝对速率常数。苯甲酰基自由基加成到丙烯酸正丁酯的速率常数范围从 1.3 x 10(5) 到 5.5 x 10(5) M(-1) s(-1) 并且比丙烯酸正丁酯低约 2 个数量级除了由所研究酮的 α 裂解产生的反自由基之外。已经进行了密度泛函理论计算,以使观察到的引发自由基的反应性合理化。通过酰基和双(酰基)氧化膦的光解产生的磷中心自由基的计算表明,P原子马利肯自旋群是磷中心自由基相对反应性的指标。(2,4,6-三甲基苯甲酰基) 氧化膦的 α 裂解通过皮秒泵浦探针和纳秒步进扫描时间分辨红外光谱进行了研究。结果支持一种机制,其中 α