Kinetic Model for Off-Stoichiometric Cross-Linking Reactions of End-Linked Polymer Networks
Kinetic Model for Off-Stoichiometric Cross-Linking Reactions of End-Linked Polymer Networks
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末端连接聚合物网络的非化学计量交联反应的动力学模型
DOI：
10.1021/acs.macromol.3c00849
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发表时间：
2023
期刊：
影响因子：
5.5
通讯作者：
Olsen, Bradley D.
中科院分区：
文献类型：
--
作者：
Beech, Haley K.;Lin, Tzyy-Shyang;Mochigase, Hidenobu;Olsen, Bradley D.
末端连接的聚合物网络的形成通常被模拟为理想化的化学反应，从而产生无缺陷的网络。然而，许多广泛使用的工业过程，包括铂催化的乙烯基硅烷交联聚(二甲基硅氧烷)(PDMS)，都是机械复杂的，涉及到各种副反应。在这里，动力学图论(KGT)模型被更新以解释非化学计量比的反应基团和副反应，通过添加两个合适的参数来表示竞争副反应的相对速率和副交联事件的概率。更新的KGT输出每种结类型的布居，根据这些布居计算两种起始材料的反应命运。用非线性Miller-Macosko理论(MMT)计算了网络的弹性有效性，更新后的理论考虑了副反应和侧交联反应。MMT在非化学计量数据上得到了验证，并在这里被选中，因为它能够解释一系列有效的连接功能。结合使用，最新的KGT和MMT提供了弹性估计，捕捉了PDMS网络中在非化学计量比硅烷/烯烃比例下观察到的弹性模量的实验峰值。托马斯湖断裂理论和微网断裂理论随后被用来估算撕裂能，在非化学计量比处显示出类似的峰值，与实验数据定性一致。这个模型在交联化学产生更复杂的反应网络的系统中很有用，这使得它与许多类别的聚合物网络化学有关，在这些化学中，经典理论可能不能充分地捕捉网络行为。
The formation of end-linked polymer networks is commonly modeled as idealized chemical reactions, resulting in defect-free networks. However, many widely used industrial processes including platinum-catalyzed vinyl-silane cross-linking of poly(dimethylsiloxane) (PDMS) are mechanistically complex and involve a variety of side reactions. Here, a kinetic graph theory (KGT) model was updated to account for off-stoichiometric reactive groups and side reactions by adding two fitting parameters representing the relative rate of competing side reactions and the probability of side cross-linking events. The updated KGT outputs the population of each junction type from which the reaction fates of both starting materials are calculated. The elastic effectiveness of the resulting network is calculated with the nonlinear Miller–Macosko theory (MMT), updated to account for side reactions and side cross-linking. The MMT was validated on off-stoichiometric data and was chosen here for its ability to account for a range of effective junction functionalities. Combined, the updated KGT and MMT provide elasticity estimates that capture the experimental peak in elastic modulus observed at an off-stoichiometric silane/alkene ratio in PDMS networks. Both the Lake Thomas and micronetwork fracture theories were subsequently used to estimate the tearing energy, showing a similar peak at off-stoichiometric ratios in qualitative agreement with experimental data. This model is useful in systems where the cross-linking chemistry yields more complex reaction networks, making it relevant to many classes of polymer network chemistry where classical theories may not adequately capture network behavior.
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--
发表时间：
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期刊：
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影响因子：
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DOI：
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发表时间：
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期刊：
影响因子：
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