Electron spin resonance study of the homopolymerization of aromatic bismaleimides
Electron spin resonance study of the homopolymerization of aromatic bismaleimides
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DOI：
10.1016/s0032-3861(98)00023-8
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发表时间：
1998-11-01
期刊：
影响因子：
4.6
通讯作者：
Pomery, PJ
中科院分区：
文献类型：
--
作者：
Hopewell, JL;Hill, DJT;Pomery, PJ
马来酰亚胺均聚可由马来酰亚胺单体引发而无需添加引发剂。这种自引发被认为是通过马来酰亚胺基团之间形成的供体-受体复合物发生的。原位电子自旋共振（e.s.r.）用光谱技术研究了1，1 '-（亚甲基二-4，1-亚苯基）双马来酰亚胺（MDP-BMI）在一定温度范围内的自由基均聚反应。在180至230 ℃的聚合温度下测量总自由基浓度作为时间的函数。通过对e.s.r.从不同的马来酰亚胺单体，MDP-BMI，N-苯基马来酰亚胺（NPM）和1，1 ′-[亚甲基双-（2，6-二乙基-4，1-亚苯基）]双马来酰亚胺（MDEP-BMI），有和没有自由基引发剂的光谱，可以确定e.s.r.信号由于各种自由基物种。在由MDP-BMI形成的聚合物链上观察到不反应的二苯基亚甲基自由基。存在包括由于传播自由基而产生的信号的附加光谱特征。含有自由基引发剂的马来酰亚胺也表现出一个宽的双峰信号分配给从马来酰亚胺双键的氢提取形成的乙烯基自由基。从NPM和MDEP-BMI单体的光谱的比较，无论有和没有自由基引发剂，它表明，马来酰亚胺传播自由基给出了一个非常窄的，单峰的esr，峰与以前报道的四线信号完全不同。(C)1998爱思唯尔科技有限公司版权所有。
Maleimide homopolymerization can be initiated by the maleimide monomer without the need for added initiator. This self-initiation is believed to occur through a donor-acceptor complex formed between maleimide groups. An in-situ electron spin resonance (e.s.r.) spectroscopic technique was used to study the free-radical homopolymerization of 1,1'-(methylenedi-4,1-phenylene)bismaleimide (MDP-BMI) over a range of temperatures. Total radical concentrations were measured as a function of time at polymerization temperatures from 180 to 230 degrees C. By analysis of the e.s.r. spectra from different maleimide monomers, MDP-BMI, N-phenylmaleimide (NPM) and 1,1'-[methylenebis-(2,6-diethyl-4,1-phenylene)] bismaleimide (MDEP-BMI), with and without free-radical initiators, it was possible to identify the e.s.r. signals due to various radical species. Unreactive diphenylmethylene radicals were observed on the polymer chains formed from MDP-BMI. Additional spectral features are present that include the signal due to the propagating radical. Maleimides containing free-radical initiator also exhibited a broad doublet signal assigned to a vinyl radical formed by hydrogen abstraction from the maleimide double bond. From comparison of the spectra of NPM and MDEP-BMI monomers, both with and without free-radical initiators, it was shown that the maleimide propagating radical gives an unusually narrow, singlet e.s.r, peak quite different from the four-line signal previously reported. (C) 1998 Elsevier Science Ltd. All rights reserved.