Topological Structure of Networks Formed from Symmetric Four-Arm Precursors
Topological Structure of Networks Formed from Symmetric Four-Arm Precursors
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DOI：
10.1021/acs.macromol.7b01829
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发表时间：
2018-02-13
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：
Lin, Tzyy-Shyang;Wang, Rui;Olsen, Bradley D.
通过偶联两种不同的四臂星形聚合物形成的凝胶导致具有高强度和低空间异质性的聚合物网络。然而，与所有真实的聚合物网络一样，这些材料包含影响其性能的拓扑缺陷。在这项研究中，利用动力学图论和蒙特卡罗模拟研究了对称四臂星形聚合物前驱体通过A-B型末端连接形成的结构和循环缺陷。虽然前体化学禁止由奇数个连接点构成的环，但发现次级环的数量和相关性随着前体浓度的降低而增加。这抑制了凝胶化，并且通过拓扑模拟定量预测了凝胶点的延迟。此外，与不对称双功能-四功能前体形成的网络的比较表明，对称系统中由 2n 个连接点组成的环的行为与不对称系统中由 n 个连接点组成的环的行为类似，这表明化学上不同的网络之间存在相似性。
Gels formed by coupling two different four-arm star polymers lead to polymer networks with high strength and low spatial heterogeneity. However, like all real polymer networks, these materials contain topological defects which affect their properties. In this study, kinetic graph theory and Monte Carlo simulation are used to investigate the structure and cyclic defects formed via A-B type end-linking of symmetric tetra-arm star polymer precursors. While loops constituting of odd number of junctions are forbidden by precursor chemistry, the amount and the correlation of secondary loops are found to increase with decreasing precursor concentration. This suppresses gelation, and the delay of gel point is quantitatively predicted by the topological simulations. Furthermore, comparison with network formed with asymmetric bifunctional-tetrafunctional precursors revealed that the behavior of loops consisting of 2n junctions in the symmetric system is analogous to the behavior of loops consisting of n junctions in the asymmetrical system, suggesting analogies between chemically distinct networks.