Structural aspects and electronic states of polyuret—construction of robust extended systems with nonbonding flat bands
Structural aspects and electronic states of polyuret—construction of robust extended systems with nonbonding flat bands
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DOI：
10.1038/s41428-020-0349-2
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发表时间：
2020-04
期刊：
影响因子：
2.8
通讯作者：
Yiming Liu;M. Hatanaka;M. Miyasaka
中科院分区：
文献类型：
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作者：
Yiming Liu;M. Hatanaka;M. Miyasaka
在一些早期的研究中，异氰酸的聚合物被LieBig和Wöhler称为氰化物(Cyamelid)，其中它被认为是异氰酸和三聚氰酸的链状聚合物的混合物。尽管人们已经知道了链状聚合物的基本结构，但对它的表征还不是很好。在此，我们聚合异氰酸，并对所得聚合物进行提纯，得到白色粉末。用红外光谱、拉曼光谱、紫外光谱、X-射线衍射分析和谱带计算对该粉末进行了表征。类似于尿素的扩展体系，例如二缩二脲、三缩二脲和更高级的低聚物，我们将这种聚合物称为聚脲。关于可能的顺式/反式异构化，对聚脲的结构化学进行了彻底的探索。由于尿素部分的非成键特性，这种聚合物在边界水平上具有平坦的带状结构。我们建议这种化合物不再被称为氰化物或多异氰酸酯，以避免与上述未表征的混合物或异氰酸酯-侧链聚合物混淆。
The polymer of isocyanic acid has been referred to as cyamelide (cyamelid) by Liebig and Wöhler in some early studies, in which it was considered a mixture of chain polymers of isocyanic acid and cyanuric acid. Despite the knowledge of its fundamental structure, the chain polymeric compound has not been well characterized. We herein polymerized isocyanic acid and purified the resultant polymer to obtain a white powder. This powder was characterized by using IR, Raman, and UV spectroscopies; X-ray diffraction analysis; and band calculations. Analogous to the extended systems of urea, e.g., biuret, triuret, and higher oligomers, we refer to this polymer as polyuret. The structural chemistry of the polyuret was thoroughly explored with regard to possiblecis/trans-isomerism. This polymer has flat bands at the frontier levels due to the nonbonding character of the urea moieties. We suggest that this compound should no longer be referred to as cyamelide or polyisocyanate to avoid confusion with the aforementioned uncharacterized mixture or with isocyanate-pendant polymers.