不同链股密度的星型聚合物网络断裂的幻影链模拟
Phantom chain simulations for fracture of star polymer networks with various strand densities
AI总结：
本研究通过Brownian dynamics模拟不同链股密度的星型聚合物网络，发现以环秩或模量归一化后的断裂特性可形成依赖于浓度的主曲线，表明断裂特性不能仅由模量描述。
摘要：
尽管进行了许多尝试，聚合物网络的断裂与结构之间的关系仍有待阐明。针对这一问题，一项关于幻影链模拟的近期研究 [Macromolecules, 56, 9359 (2023)] 表明，如果将具有不同节点官能度和转化率的聚合物网络的断裂特性针对环秩进行绘图，它们将落在主曲线上。在本研究中，我们将模拟扩展到预聚物浓度对环秩与断裂特性之间关系的影响，浓度范围为 1<c/c^*<8，涉及重叠浓度 c^*。我们通过 Brownian dynamics 模拟，将分支臂数 f 从 1 变化到 8，转化率 ϕ_c 从 0.6 变化到 0.95，通过不同链之间的末端连接反应，从星型分支幻影珠-簧链的溶胶中创建了网络。对于生成的网络，环秩 ξ 与 mean-field theory 相符。网络在能量最小化下被单轴拉伸直至断裂，以获得模量 G、断裂应变 ε_b、断裂应力 σ_b 和断裂功 W_b。以分支点密度 \u{psion}_br 归一化后，不同 f 和 ϕ_c 数据的 G/\u{psion}_br、ε_b、σ_b/\u{psion}_br 和 W_b/\u{psion}_br 在针对 ξ 绘图时形成主曲线。主曲线依赖于 c；随着 c 增加，所有力学特性单调增加。如果将 σ_b/\u{psion}_br 和 W_b/\u{psion}_br 针对 G/\u{psion}_br 绘图，不同 f 和 ϕ_c 的数据落在主曲线上，但依赖于 c。因此，对于所研究的能量最小化幻影链网络，断裂特性不能仅由模量来描述。
英文摘要：
Despite many attempts, the relation between fracture and structure of polymer networks is yet to be clarified. For this problem, a recent study for phantom chain simulations [Macromolecules, 56, 9359 (2023)] has demonstrated that the fracture characteristics obtained for polymer networks with various node functionalities and conversion ratios lie on master curves if they are plotted against cycle rank. In this study, we extended the simulation to the effect of prepolymer concentration on the relationships between cycle rank and fracture characteristics within the concentration range of 1<c/c^*<8, concerning the overlapping concentration c^*. We created networks from sols of star-branched phantom bead-spring chains via end-linking reaction between different chains through Brownian dynamics simulations with varying the number of branching arms f from 1 to 8, and the conversion ratio ϕ_c from 0.6 to 0.95. For the resultant networks, cycle rank ξ was consistent with the mean-field theory. The networks were uniaxially stretched with energy minimization until break to obtain modulus G, strain at break ε_b, stress at break σ_b, and work for fracture W_b. With the branch point density \u{psion}_br, G/\u{psion}_br, ε_b, σ_b/\u{psion}_br, and W_b/\u{psion}_br of the data for various f and ϕ_c draw master curves if plotted against ξ. The master curves depend on c; as c increases, all the mechanical characteristics monotonically increase. If we plot σ_b/\u{psion}_br and W_b/\u{psion}_br against G/\u{psion}_br, the data for various f and ϕ_c lie on master curves but depending on c. Consequently, the fracture characteristics are not solely described by modulus for the examined energy-minimized phantom chain networks.
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