Ring-Expansion/Contraction Radical Crossover Reactions of Cyclic Alkoxyamines: A Mechanism for Ring Expansion-Controlled Radical Polymerization
Ring-Expansion/Contraction Radical Crossover Reactions of Cyclic Alkoxyamines: A Mechanism for Ring Expansion-Controlled Radical Polymerization
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DOI：
10.3390/polym10060638
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发表时间：
2018-06
期刊：
影响因子：
5
通讯作者：
A. Narumi;Tetsuya Kobayashi;Masatsugu Yamada;W. Binder;Keigo Matsuda;Montaser Shaykoon Ahmed Shaykoon-Montaser-Shaykoon-Ahmed-Shaykoon-153
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作者：
A. Narumi;Tetsuya Kobayashi;Masatsugu Yamada;W. Binder;Keigo Matsuda;Montaser Shaykoon Ahmed Shaykoon-Montaser-Shaykoon-Ahmed-Shaykoon-153
大环聚合物是一类重要的大分子，其显示出减小的回转半径或不可能缠结。一种罕见的合成方法是从环状烷氧基胺开始的环膨胀控制的自由基“乙烯基”聚合。在这里，我们描述了环状烷氧基胺的扩环自由基交叉反应，该反应与聚合体系中的链增长反应并行。自由基交换反应在105-125 °C下广泛发生，最终产生具有多个固有动态共价键（NOC键）的高分子量聚合物。还描述了随后的缩环自由基交叉反应和第二扩环自由基交叉反应。通过分子量分布和NOC键的残留率（φ %），表明相应三个阶段的主要产物具有环状形态。特别是，高φ值范围从ca.对于该环状烷氧基胺体系，实现了80%至98%。该结果验证了该系统作为证明扩环“乙烯基”聚合的工具的高可用性，该扩环“乙烯基”聚合允许它们通过一步乙烯基聚合来生产大环聚合物。
Macrocyclic polymers present an important class of macromolecules, displaying the reduced radius of gyration or impossibility to entangle. A rare approach for their synthesis is the ring expansion-controlled radical “vinyl” polymerization, starting from a cyclic alkoxyamine. We here describe ring-expansion radical crossover reactions of cyclic alkoxyamines which run in parallel to chain-propagation reactions in the polymerization system. The radical crossover reactions extensively occurred at 105–125 °C, eventually producing high molecular weight polymers with multiple inherent dynamic covalent bonds (NOC bonds). A subsequent ring-contraction radical crossover reaction and the second ring-expansion radical crossover reaction are also described. The major products for the respective three stages were shown to possess cyclic morphologies by the molecular weight profiles and the residual ratios for the NOC bonds (φ in %). In particular, the high φ values ranging from ca. 80% to 98% were achieved for this cyclic alkoxyamine system. This result verifies the high availability of this system as a tool demonstrating the ring-expansion “vinyl” polymerization that allows them to produce macrocyclic polymers via a one-step vinyl polymerization.