Molecular dynamics simulation of associative polymers: Understanding linear viscoelasticity from the sticky Rouse model
Molecular dynamics simulation of associative polymers: Understanding linear viscoelasticity from the sticky Rouse model
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缔合聚合物的分子动力学模拟：从粘性劳斯模型理解线性粘弹性
DOI：
10.1122/8.0000218
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发表时间：
2021-07-01
影响因子：
3.3
通讯作者：
Tang, Ping
中科院分区：
文献类型：
--
作者：
Jiang, Nuofei;Zhang, Hongdong;Tang, Ping
带有缔合基团（APs）的聚合物具有优异的粘弹性。在我们小组最近发表的一篇论文中[Jiang等人，Macromolecules 53, 3438-3451(2020)]，提出了一个单链粘性Rouse模型（SRM）来描述APs在没有纠缠效应的情况下的线性粘弹性。本文对均匀分布胶黏剂的无纠缠熔体进行了平衡分子动力学模拟，并从SRM角度对其动力学特性进行了分析。提出了一种带有封顶贴纸的链模型，从而保证了仿真系统中具有良好定义的关联化学。从链的质心扩散中提取了胶黏剂的相对有效摩擦系数，这是SRM中的关键参数，发现它与完全凝胶化网络中缔合反应的动力学一致。在此基础上，在不拟合参数的情况下，从SRM中预测了线性松弛模量和段扩散函数，结果与模拟结果在定量上一致，表明SRM在连接不同分子水平上的动态特性方面是有效的。在SRM的情况下，松弛模式的变化和有效链中心的定义至关重要。最后，将上述分析从SRM成功推广到具有不对称链的仿真系统。这些模拟结果有力地支持了SRM作为AP线性流变的分子模型。
Polymers bearing associative groups (APs) are characterized by their fantastic viscoelastic behaviors. In a work recently published by our group [Jiang et al., Macromolecules 53, 3438-3451 (2020)], a single chain sticky Rouse model (SRM) is proposed to describe the linear viscoelasticity of APs without the entanglement effect. In this work, equilibrium molecular dynamics simulation of an unentangled melt of an AP with uniformly distributed stickers is carried out, and the dynamic properties are simultaneously analyzed from the SRM. A chain model with capped stickers is proposed so that a well-defined association chemistry is promised in the simulation system. The relative effective frictional coefficient of stickers, which is the key parameter in the SRM, is extracted from the chain center-of-mass diffusion, and it is found to be consistent with the dynamics of associative reaction in the fully gelated network. Based on this, a linear relaxation modulus and segmental diffusion functions are predicted from the SRM without fitting parameters, and these are found to quantitatively agree with the simulation results, showing the effectiveness of the SRM in connecting the dynamic properties at different molecular levels. The change in relaxation modes and the definition of the effective chain center are found to be crucial in the scenario of the SRM. Finally, the above analysis from the SRM is successfully extended to the simulation system with asymmetric chains. All these simulation results strongly support the SRM as a molecular model for the linear rheology of AP.