PLP-ESR monitoring of midchain radicals in n-butyl acrylate polymerization
PLP-ESR monitoring of midchain radicals in n-butyl acrylate polymerization
复制标题
丙烯酸正丁酯聚合中链自由基的 PLP-ESR 监测
DOI：
10.1021/ma050198d
复制
发表时间：
2005
期刊：
影响因子：
5.5
通讯作者：
M. Buback
中科院分区：
文献类型：
--
作者：
R. Willemse;A. Herk;E. Panchenko;Thomas Junkers;M. Buback
用ESR波谱法测定了丙烯酸正丁酯脉冲激光聚合（PLP）中两种自由基的含量。在单体浓度为0.50至2.53 mol L-1、温度为-50至70 °C的甲苯溶液中，通过重复频率为20 Hz的351 nm准分子激光脉冲诱导聚合。在低程度的单体转化率获得的ESR光谱可以充分表示由叠加六组分四线光谱分配到二级传播自由基（SPR）和九线光谱分配到叔中链自由基产生的反咬（MCR 1 s）。后一种物质对总自由基浓度的贡献百分比，由SPR通过1，5-H位移反咬反应产生，在−50 °C时可以忽略不计，在70 °C时接近80%。SPR到MCR 1物种的转变使施加激光脉冲后时间t与生长自由基的大小的线性相关性失效。T...
The percentage of two types of free radicals occurring within n-butyl acrylate pulsed laser polymerization (PLP) has been measured via ESR spectroscopy. Polymerization in solution of toluene, at monomer concentrations between 0.50 and 2.53 mol L-1 and temperatures between −50 and 70 °C, was induced by 351 nm excimer laser pulses applied at a repetition rate of 20 Hz. The ESR spectra obtained at low degrees of monomer conversion may be adequately represented by superimposing a six-component four-line spectrum assigned to secondary propagating radicals (SPRs) and a nine-line spectrum assigned to tertiary midchain radicals produced by backbiting (MCR1s). The percentage contribution to total radical concentration of the latter species, which is produced from an SPR by a 1,5-H shift backbiting reaction, is negligible at −50 °C and is close to 80% at 70 °C. The transition of an SPR to a MCR1 species invalidates the linear correlation of time t after applying a laser pulse with the size of the growing radical. T...