Molecular size distribution in three dimensional polymers. I. Gelation
Molecular size distribution in three dimensional polymers. I. Gelation
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DOI：
10.1021/ja01856a061
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发表时间：
1941-07-01
影响因子：
15
通讯作者：
Flory, PJ
中科院分区：
文献类型：
--
作者：
Flory, PJ
聚合可以分为两种类型：一种是完全可溶的产物，而不管反应进行到什么程度；另一种是只要反应进行得足够远，就会产生胶凝的或不溶的产物。前一种行为是双功能体系的特征，例如，乙二醇-邻苯二甲酸反应，其中形成线性聚合物；后一种行为在更高官能团的体系中观察到，其中反应物在功能上能够产生无限大的三维分子，例如甘油-邻苯二甲酸反应。由于只有在三维空间中存在无限增长的可能性时，胶凝才会发生，因此得出胶凝是无限大分子形成的结果的结论是不可抗拒的。卡罗瑟斯指出，当每个初始的单体分子形成一个分子间的连接时，所有可聚合的物质必须结合成一个巨大的分子，而进一步的分子间反应的可能性就被耗尽了。例如，在2摩尔甘油与3摩尔邻苯二甲酸的反应中，官能团的分子间反应程度不能超过5/e，即83.3%，每5个单位有6个潜在的键。然而，卡罗瑟斯认识到，在较低程度的反应中可以形成无限大的分子。例如，一小部分单位可能结合形成“无限”分子，而其余的
Polymerizations may be divided into two types: those which lead exclusively to soluble products regardless of the extent to which the reaction is carried toward completion, and those which lead to gelled, or insoluble, products provided that the reaction is carried far enough. The former be-havior is characteristic of bifunctional systems, e. g., the ethylene glycol-phthalic acid reaction, in which linear polymers are formed; the latter behavior is observed in systems of higher func-tionality where the reactants are functionally capable of producing indefinitely large three-dimensional molecules, e. g., the glycerol-phthalic acid reaction. Since gelation occurs only when there is the possibility of unlimited growth in three dimensions, the conclusion that it is the result of the formation of infinitely3 large molecules has been irresistible. 4 Carothers5 pointed out that when one intermolecular linkage has been formed per initial monomeric molecule, all of the polymerizable material must be bound into one gigantic molecule, and possibilities for further intermolecular reaction are exhausted. In the re-action of twomoles of glycerol with three of phtha-lic acid, for example, the extent of intermolecular reaction of the functional groups could not exceed5/e, or 83.3%, there being six potential linkages per five units. It was recognized by Carothers, however, that indefinitely large molecules might be formed at lower extents of reaction. 6 For example, a small fraction of the units might unite to form “infinite” 3 molecules, while the remaining