Contrary to thermosets, vitrimers adjust their topology upon heating without loss of network integrity. Here, the proposed simulation methodology utilizes coarse-grained molecular dynamics in conjunction with a Monte Carlo method to capture the network integrity and flowability of vitrimers at high temperatures. The model vitrimer shows two transition temperatures. In addition to the conventional glass transition temperature, the topology freezing temperature is detected from the volumetric and rheological data. In the glassy state, the mobility of the vitrimer and thermoset is identical, whereas increasing the temperature results in a diffusive behavior in the vitrimer. The rheological data capture the main feature of vitrimers, which is the terminal regime of the elastic modulus at low frequencies. The zero-shear viscosity of the model vitrimer follows an Arrhenius-like temperature dependence at temperatures above the topology freezing temperature. The horizontal shift factors obtained from collapsing the rheological data onto master curves also display the same temperature dependence. Simulations reveal that the lifetime of the exchangeable bonds determines the rheology and dynamics of these networks. When the rate of the deformation is higher than the rate of the bond exchange, the system behaves as a typical thermoset, while at lower rates, the vitrimer behaves as a viscous liquid.

中文翻译：

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Vitrimers的体积和流变性质：混合分子动力学和蒙特卡洛模拟研究

与热固性材料相反，增容剂在加热时会调整其拓扑结构，而不会损失网络完整性。在这里，拟议的仿真方法利用粗粒度的分子动力学与蒙特卡洛方法相结合，以捕获高温下微晶聚合物的网络完整性和流动性。型号微晶玻璃显示两个转变温度。除了常规的玻璃化转变温度外，还从体积和流变数据中检测拓扑冻结温度。在玻璃态下，微晶玻璃和热固性树脂的迁移率是相同的，而升高温度会导致微晶玻璃中的扩散行为。流变数据记录了微粉体的主要特征，它是低频下弹性模量的最终形式。在高于拓扑冻结温度的温度下，模型微晶陶瓷的零剪切粘度遵循类似于阿伦尼乌斯的温度依赖性。通过将流变数据折叠到主曲线上而获得的水平位移因子也显示出相同的温度依赖性。仿真表明，可交换键的寿命决定了这些网络的流变性和动力学。当变形速率高于键交换速率时，系统表现为典型的热固性，而在较低的速率下，微晶纤维素表现为粘性液体。仿真表明，可交换键的寿命决定了这些网络的流变性和动力学。当变形速率高于键交换速率时，系统表现为典型的热固性，而在较低的速率下，微晶纤维素表现为粘性液体。仿真表明，可交换键的寿命决定了这些网络的流变性和动力学。当变形速率高于键交换速率时，系统表现为典型的热固性，而在较低的速率下，微晶纤维素表现为粘性液体。