In the present work, method of moments is used to model the molecular weight distribution (MWD) of polypropylene glycol (PPG) produced with ring-opening polymerization of propylene oxide catalyzed by double metal complex (DMC), and an explicit expression about the polydispersity index (PDI) of PPG is obtained. The simulated results indicate that decreasing the initial concentration ratio of monomer to total chains (K₁) or increasing the rate constant ratio of chain transfer to propagation (K₂) leads to smaller PDI. Reducing the concentration of DMC can induce larger PDI. When the PPG's initial PDI (i.e., PDI of initiator) increases, PDI of the final PPG grows up linearly. However, with the increase of monomer conversion, PDI increases first and then decreases, that is, there is a critical conversion. The possible lack of chain transfer at the beginning of polymerization and the insufficient chain transfer caused by increased K₁, decreased concentration of catalyst, and decreased K₂ will cause larger PDI, namely, broad MWD.

中文翻译：

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双金属配合物催化的环氧丙烷开环聚合中分子量分布的模型模拟

在本文中，采用矩量法对双金属络合物（DMC）催化的环氧丙烷开环聚合反应制得的聚丙二醇（PPG）的分子量分布（MWD）进行建模，并对多分散性进行了明确表述。获得PPG的指数（PDI）。模拟结果表明，降低单体与链的初始浓度比（K ₁）或增加链转移与传播的速率常数比（K _2）。）导致PDI较小。降低DMC的浓度可以诱导更大的PDI。当PPG的初始PDI（即发起方的PDI）增加时，最终PPG的PDI线性增长。但是，随着单体转化率的提高，PDI先升高然后降低，即存在临界转化率。聚合开始时可能缺乏链转移，以及由于K ₁增加，催化剂浓度降低和K ₂降低引起的链转移不足，将导致PDI增大，即宽MWD。