Vitrimers are polymer networks that, thanks to covalent bond exchange, combine desirable properties of thermoplastic and thermosets, such as flowability and insolubility. For this reason, vitrimers are considered to be good candidates for a number of innovative applications from self-healing soft robots to hard reprocessable materials. All these applications are related to the unusual thermomechanical behavior of vitrimers, consequence of the non-trivial interplay between the polymer network dynamics and the thermally activated chemical link exchange. Here we use solid-state rheology to investigate the properties of a recently developed epoxy-based vitrimer. The rheological analysis demonstrates that the mechanical spectrum is composed of two relaxation processes with distinct activation energies that are associated with glass dynamics and covalent bond exchange, respectively. This makes the material thermo-rheologically complex and time temperature equivalence does not apply. Nonetheless, thanks to mechanical spectral analysis in a wide range of stiffness, time and temperature, we are able to depict the time-temperature-relaxation landscape in an enough precise way to account for the two dynamical processes and recombine them to predict the mechanical moduli in a wide interval of frequencies (21 decades), from low temperatures (close to room temperature) to high temperatures (above the glass transition temperature).

中文翻译：

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解决 vitrimer 的弛豫复杂性：时间-温度非等效系统的时间-温度叠加

Vitrimer 是一种聚合物网络，由于共价键交换，结合了热塑性塑料和热固性塑料的理想特性，例如流动性和不溶解性。因此，vitrimer 被认为是从自愈软机器人到硬可再加工材料等许多创新应用的良好候选者。所有这些应用都与玻璃体不寻常的热机械行为有关，这是聚合物网络动力学和热激活化学键交换之间重要相互作用的结果。在这里，我们使用固态流变学来研究最近开发的环氧基玻璃体的特性。流变分析表明，机械谱由两个具有不同活化能的弛豫过程组成，分别与玻璃动力学和共价键交换相关。这使得材料的热流变变得复杂并且时间温度等效性不适用。尽管如此，由于在广泛的刚度、时间和温度范围内进行机械谱分析，我们能够以足够精确的方式描绘时间-温度-弛豫景观，以解释这两个动力学过程并将它们重新组合以预测机械模量在很宽的频率区间（21个十进制），从低温（接近室温）到高温（高于玻璃化转变温度）。