Dynamics in Supramolecular Polymer Networks Formed by Associating Telechelic Chains
Dynamics in Supramolecular Polymer Networks Formed by Associating Telechelic Chains
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DOI：
10.1021/acs.macromol.6b00561
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发表时间：
2016-10-11
期刊：
影响因子：
5.5
通讯作者：
Wang, Zuowei
中科院分区：
文献类型：
--
作者：
Amin, Dipesh;Likhtman, Alexei E.;Wang, Zuowei
我们提出了混合分子动力学/Monte Carlo模拟的超分子网络形成的非纠缠遥爪链与粘性端单体（或贴纸）的有限功能。粘性单体之间的可逆键合导致形成具有良好定义的尺寸分布的粘着簇，这反过来又作为瞬时聚合物网络的交联。我们研究了粘性单体缔合的动力学，拓扑结构，以及由此产生的动态和流变行为的超分子系统作为一个功能的贴纸结合能和母体聚合物链长。在临界键能4.3k（B）T以上形成了渗流瞬态网络。在高键能B>= 10 k（T）时，大部分胶都反应完全，开胶率小于1%.单个贴纸从一个集群跳到另一个集群的传统图片在能量上是不利的。我们发现这种强关联的超分子网络的动力学和流变学行为是由一个伙伴交换机制，其中的贴纸交换其相关的合作伙伴，因此释放施加的拓扑约束，通过关联和分离的贴纸集群。伴侣交换事件的特征时间随键能呈指数增长，并且比可逆键的平均寿命长2个数量级。其结果是，三个松弛制度，可以清楚地确定在应力和链端到端的矢量松弛函数以及均方位移的贴纸，这是初始劳斯制度，中间橡胶制度，和终端松弛制度。提出了一种基于微观理解的幻影链跳跃模型来描述超分子网络中的链弛豫动力学，该模型提供了与我们的模拟结果相当吻合的数值预测。
We present hybrid molecular dynamics/Monte Carlo simulations of supramolecular networks formed by unentangled telechelic chains with sticky end monomers (or stickers) of finite functionality. The reversible bonding between sticky monomers leads to the formation of sticker clusters with well-defined size distribution, which in turn work as cross-links for transient polymer networks. We study the kinetics of sticky monomer association, the topological structure, and the resulting dynamic and rheological behavior of the supramolecular systems as a function of the sticker bonding energy epsilon and the parent polymer chain length. Percolated transient networks are formed above a threshold bonding energy around 4.3k(B)T. At high bonding energies epsilon >= 10k(B)T, the majority of the stickers are fully reacted and the fraction of open stickers is less than 1%. The conventional picture of a single sticker hopping from one cluster to another is energetically unfavorable. We find the dynamic and rheological behavior of such strongly associated supramolecular networks are dominated by a partner exchange mechanism in which the stickers exchange their associated partners, and so release the imposed topological constraints, through the association and disassociation of sticker clusters. The characteristic time of the partner exchange events grows exponentially with the bonding energy and is up to 2 orders of magnitude longer than the average lifetime of the reversible bonds. As a result, three relaxation regimes can be clearly identified in the stress and chain end-to-end vector relaxation functions as well as the mean-squared displacements of the stickers, which are the initial Rouse regime, the intermediate rubbery regime, and the terminal relaxation regime. A phantom chain hopping model based on the microscopic understanding is proposed to describe the chain relaxation dynamics in the supramolecular networks, which provides numerical predictions in reasonably good agreement with our simulation results.