Time-resolved Fourier-transform and continuous-wave ESR studies on photo-initiated polymerization
Time-resolved Fourier-transform and continuous-wave ESR studies on photo-initiated polymerization
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光引发聚合的时间分辨傅立叶变换和连续波 ESR 研究
DOI：
10.1007/bf03162264
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
K. Kuwata
中科院分区：
文献类型：
--
作者：
Y. Mizuta;N. Morishita;K. Kuwata
采用连续波电子自旋共振（cw ESR）和傅里叶变换（FT）ESR研究了2，4，6-三甲基苯甲酰基二苯基氧化膦（TMDPO）光裂解形成的二苯基膦酰基（DPO）自由基引发乙烯基单体的自由基聚合反应。乙酸乙烯酯，乙基乙烯基醚，苯乙烯，甲基丙烯酸甲酯（MMA），和异戊二烯的时间分辨cw ESR观察到良好解决的超精细结构（HFS的）的起始自由基。这些起始自由基的形成率和自旋-晶格弛豫由时间分辨FT ESR确定。在MMA和异戊二烯的聚合反应中，首次用时间分辨的顺时针ESR观察到了它们的高分辨自由基，从而发现了主要增长自由基。在包括自旋-晶格弛豫的动力学分析的基础上，通过模拟MMA和异戊二烯的初始增长自由基的FT ESR时间曲线，确定了自由基的生成速率和自旋-晶格弛豫速率。发现初级传播步骤的速率比通过稳态测量获得的整个传播步骤的平均值大两个数量级。
Radical polymerization of vinyl monomers as initiated by the diphenylphosphinoyl (DPO) radical which is formed by the photo-cleavage of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TMDPO) was investigated by continuous-wave electron spin resonance (cw ESR) and Fourier-transform (FT) ESR. Well-resolved hyperfine structures (hfs’s) of the starting radicals were observed by the time-resolved cw ESR for vinyl acetate, ethyl vinyl ether, styrene, methyl methacrylate (MMA), and isoprene. The rates of formation and the spin-lattice relaxation were determined by time-resolved FT ESR for these starting radicals. In the polymerization of MMA and isoprene the primary propagating radicals were found for the first time by the observation of their well-resolved hfs’s with timeresolved cw ESR. On the basis of the kinetic analysis including the spin-lattice relaxation, the rates of formation and the spin-lattice relaxation were determined by simulation of the time profile of FT ESR for the primary propagating radicals of MMA and isoprene. The rate of the primary propagating step was found to be by two orders greater than an average value of whole propagating steps as obtained by a steady-state measurement.