Discrete mesoscale network models, in which explicitly modeled polymer chains are replaced by implicit pairwise potentials, are capable of predicting the macroscale mechanical response of polymeric materials such as elastomers and gels, while offering greater insight into microstructural phenomena than constitutive theory or macroscale experiments alone. However, whether such mesoscale models accurately represent the molecular structures of polymer networks requires investigation during their development, particularly in the case of dynamic polymers that restructure in time. We here introduce and compare the topological and mechanical predictions of an idealized, reduced-order mesoscale approach in which only tethered dynamic bonding sites and crosslinks in a polymer’s backbone are explicitly modeled, to those of molecular theory and a Kremer–Grest, coarse-grained molecular dynamics approach. We find that for short chain networks (∼12 Kuhn lengths per chain segment) at intermediate polymer packing fractions, undergoing relatively slow loading rates (compared to the monomer diffusion rate), the mesoscale approach reasonably reproduces the chain conformations, bond kinetic rates, and ensemble stress responses predicted by molecular theory and the bead–spring model. Further, it does so with a 90% reduction in computational cost. These savings grant the mesoscale model access to larger spatiotemporal domains than conventional molecular dynamics, enabling simulation of large deformations as well as durations approaching experimental timescales (e.g., those utilized in dynamic mechanical analysis). While the model investigated is for monodisperse polymer networks in theta-solvent, without entanglement, charge interactions, long-range dynamic bond interactions, or other confounding physical effects, this work highlights the utility of these models and lays a foundational groundwork for the incorporation of such phenomena moving forward.

中文翻译：

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动态弹性体和凝胶中尺度建模的基础框架


离散的中尺度网络模型，其中显式建模的聚合物链被隐含的成对电位所取代，能够预测聚合物材料（如弹性体和凝胶）的宏观力学响应，同时比单独的本构理论或宏观尺度实验更深入地了解微观结构现象。然而，这种中尺度模型是否准确地表示聚合物网络的分子结构需要在它们的开发过程中进行研究，特别是在动态聚合物随时间重组的情况下。我们在这里介绍并比较了理想化、降阶中尺度方法的拓扑和力学预测，其中仅显式建模聚合物骨架中的栓系动态键合位点和交联，与分子理论和 Kremer-Grest 粗粒度分子动力学方法的预测。我们发现，对于中等聚合物堆积分数的短链网络（每条链段 ∼12 Kuhn 长度），负载速率相对较慢（与单体扩散速率相比），介尺度方法合理地再现了分子理论和珠子-弹簧模型预测的链构象、键动力学速率和集合应力响应。此外，它还将计算成本降低了 90%。这些节省使介尺度模型能够访问比传统分子动力学更大的时空域，从而能够模拟大变形以及接近实验时间尺度的持续时间（例如，用于动态力学分析的持续时间）。 虽然所研究的模型是针对 θ 溶剂中的单分散聚合物网络，没有纠缠、电荷相互作用、长程动态键相互作用或其他混杂的物理效应，但这项工作突出了这些模型的实用性，并为进一步整合此类现象奠定了基础。