E.s.r. measurements of the propagation rate coefficient for styrene free radical polymerisation
E.s.r. measurements of the propagation rate coefficient for styrene free radical polymerisation
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E.s.r.
DOI：
10.1016/s0032-3861(97)00507-7
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发表时间：
1998
期刊：
影响因子：
4.6
通讯作者：
R. Gilbert
中科院分区：
文献类型：
--
作者：
M. Tonge;A. Kajiwara;M. Kamachi;R. Gilbert
电子自旋共振（e.s.r.）由于可以直接观察到增长的自由基浓度，所以光谱学对于测量自由基聚合中的增长速率系数（KP）应该是有用的。然而，在以前的研究中，kp值通常是不一致的，并不同意从其他公认的实验技术，如脉冲激光聚合的数据。这项研究表明，对于苯乙烯，可以获得一致性，但只有当实验条件的选择，使足够高的分子量的聚合物形成，否则可能会测量不正确的速率常数。测得的Arrhenius参数与IUPAC认可的数据吻合较好。在343 K的热和光化学引发的实验的值被发现是一致的，这表明光引发的系统可以在基态聚合。一些以前不一致的数据可以解释在实验条件的选择。
Electron spin resonance (e.s.r.) spectroscopy should be useful for the measurement of propagation rate coefficients (kp) in free radical polymerisations, since the propagating radical concentration can be directly observed. However, in previous studies, kpvalues have generally been inconsistent, and disagreed with data from other accepted experimental techniques, such as pulsed laser polymerisation. This study shows that for styrene, consistency can be obtained, but only when experimental conditions are selected such that polymer of sufficiently high molecular weight is formed; otherwise incorrect rate constants may be measured. The measured Arrhenius parameters were in good agreement with IUPAC accepted data. The values at 343 K for both thermally and photochemically initiated experiments were found to be consistent, suggesting that photoinitiated systems may polymerise in the ground state. Some previously inconsistent data could be explained in terms of selection of experimental conditions.