Molecular structure and rubber-like elasticity II. The stereochemistry of chain polymers
Molecular structure and rubber-like elasticity II. The stereochemistry of chain polymers
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分子结构和橡胶弹性II．
DOI：
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发表时间：
1942
期刊：
影响因子：
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通讯作者：
C. Bunn
中科院分区：
文献类型：
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作者：
C. Bunn
对含有两个或多个单键碳原子的分子的已知结构的调查表明，交错键构型是有利的。有人建议，这些分子可能是一个一般规则的例子-“交错键的原则”-它指定的键的位置为连续的单键连接的碳原子，就像“四面体原则”指定的键的位置在任何一个碳原子。如果这是真的，就有可能预测分子构型。所有的交替构型都遵循交错键的原则，随着碳原子数的增加而迅速增加，但是，一个特定分子的最可能构型有时可以根据几何基础来预测。描述了较简单的碳链类型。结晶长链聚合物中的链型有时可以从分子的同一周期的知识推导出来，这很容易从X射线或电子衍射图中找到。交错键原理也适用于含有单键连接的氮、氧和硫原子的分子。因此，含有这些原子的杂原子链的构型与碳链的构型是相同类型的。在含有双键的分子中，交错键的原理可能仍然有效，一个双键在熟悉的简单几何方法中被看作是两个扭曲的单键。杜仲胶、橡胶和氯丁橡胶的非平面链状结构是由两种因素共同作用的结果：一是错列键原理，二是甲基或氯侧取代基与链中特定的OH o基团之间的排斥作用。
A survey of the known structures of molecules containing two or more singly linked carbon atoms has shown that the staggered bond configuration is favoured. It is suggested that these molecules may be examples of a general rule—the ‘principle of staggered bonds’—which specifies the bond positions for successions of singly linked carbon atoms, just as the ‘tetrahedral principle’ specifies the bond positions on any one carbon atom. If this is true, it is possible to predict molecular configurations. The number of alternative configurations, all obeying the principle of staggered bonds, increases rapidly with the number of carbon atoms, but the,most probable configuration of a particular molecule can sometimes be predicted on geometrical grounds. The simpler types of carbon chain are described. The chain-type in a crystalline long-chain polymer may sometimes be deduced from a knowledge of the identity period of the molecules, which is readily found from X-ray or electron diffraction patterns. The principle of staggered bonds is also obeyed in molecules containing singly linked nitrogen, oxygen and sulphur atoms. The configurations of lietero-atomic chains containing these atoms are therefore of the same types as carbon chains. In molecules containing double bonds, the principle of staggered bonds may still be operative, a double bond being regarded in the familiar simple geometrical way as two distorted single bonds. The non-planar chain forms of gutta-percha, rubber and polychloroprene are attributed to the cooperation of two influences: the principle of staggered bonds, and the repulsion between methyl or chlorine side substituents and particular 0H o groups in the chains.