Modeling of Chain Length and Long-Chain Branching Distributions in Free-Radical Polymerization
Modeling of Chain Length and Long-Chain Branching Distributions in Free-Radical Polymerization
复制标题
自由基聚合中链长和长链支化分布的建模
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
R. Hutchinson
中科院分区：
文献类型：
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作者：
R. Hutchinson
系统研究了长链支化和β-断裂反应对充分混合的连续反应器中生产的聚合物的完整分子量（MW）和支化密度分布的影响。 PREDICI® 软件包中开发并实施了对两个所得聚合物片段之间的断链分布上的支化点的改进统计描述。模拟用于说明支化密度分布不能提供系统中平均支化的良好视觉指示；为了对椅子进行适当的平均，必须进行长度分布。结果表明，当断裂是主要的MW控制机制时，即使存在支化，链长度也趋于最可能的分布。此外，只要相对于其在反应器中的平均停留时间，每条链发生足够数量的顺断事件，就可以获得均匀的支化密度分布。当与另一种分子量控制机制（例如转移到溶剂）结合时，少量的断裂可以导致形成具有不对称或双峰特征的链长分布，并减少高分子量尾部和多分散性。
The effect of long-chain branching and β- scission reactions on the complete molecular weight (MW) and branching density distributions of polymer pro- duced in a well-mixed continuous reactor has been sys- ematically studied. An improved statistical description of ow branch points on a scissioning chain distribute between the two resulting polymer fragments has been developed and implemented in the PREDICI® software package, Simulations are used to illustrate that the branching density distribution does not provide a good visual ndication of average brarching in the system; appropriate averaging aeross the chair, length distribution must be performed, It is shown that chain lengths tend to the most probable distribution even in the presence of branching when scission is the principle MW-controlling mechanιsm. Furthemore, a uniform branchingdensity distribution is obtained, provided that a sufficient number of sciston events occur per chain relative to its average residence time in the reactor. Smaller amounts of scission, when combined with another MW-controlling mechanism such as transfer to solvent, can lead to the formation of chain length distributions with asymmetric or bimodal features as well as reducing the high-MW tail and polydispersity.