Anionic Polymerization Mechanism of Acrylonitrile Trimer Anions: Key Branching Point between Cyclization and Chain Propagation
Anionic Polymerization Mechanism of Acrylonitrile Trimer Anions: Key Branching Point between Cyclization and Chain Propagation
复制标题
丙烯腈三聚物阴离子的阴离子聚合机理：环化与链增长之间的关键分支点
DOI：
10.1021/jp305291r
复制
发表时间：
2012
期刊：
影响因子：
2.9
通讯作者：
and K. Ohno
中科院分区：
文献类型：
--
作者：
K. Ohshimo;Y. Inokuchi;T. Ebata;and K. Ohno
气相中乙烯基化合物的团簇阴离子是阴离子聚合反应初始阶段最简单的微观模型之一。在此，我们描述了我们的研究丙烯腈（AN; CH 2 <$CHCN）三聚体阴离子的阴离子聚合的初始阶段的机制。在质谱和光电子能谱研究中发现（AN）3-的环状低聚物，而在Ar标记的（AN）3-的红外光解（IRPD）谱中只发现链状低聚物。在计算了（AN）3-的聚合途径的基础上，我们认为链状低聚物是（AN）3-环化反应的反应中间体。发现（AN）3-链低聚物的旋转异构化是（AN）3-环化反应的瓶颈。为了通过链增长形成（AN）4-链低聚物，AN分子与（AN）3-的加成应在旋转异构化之前发生。我们的结论是（AN）3-链低聚物中的旋转异构化是阴离子聚合中环化（终止）或链增长之间的关键分支点。
A cluster anion of vinyl compounds in the gaseous phase has served as one of the simplest microscopic models of the initial stages of anionic polymerization. Herein, we describe our investigations into the initial stage mechanisms of anionic polymerization of acrylonitrile (AN; CH2CHCN) trimer anions. While the cyclic oligomer is found in mass and photoelectron spectroscopic studies of (AN)3–, only the chain oligomer is found in the infrared photodissociation (IRPD) spectrum of Ar-tagged (AN)3–. On the basis of the calculated polymerization pathway of (AN)3–, we consider that the chain oligomers are the reaction intermediates in the cyclization of (AN)3–. The rotational isomerization of the (AN)3–chain oligomer is found to be the bottleneck in the cyclization of (AN)3–. To form the (AN)4–chain oligomer by chain propagation, the addition of an AN molecule to (AN)3–should occur prior to the rotational isomerization. We conclude that the rotational isomerization in the (AN)3–chain oligomer is the key branching point between cyclization (termination) or chain propagation in the anionic polymerization.