Vitrimers are covalently cross-linked polymers that can be reshaped and recycled, triggered by the temperature. Well above the canonical glass transition temperature T_g, they gain malleable, thermoplastic-like properties; below, they behave as thermosets. The responsible molecular mechanism is enabled by dynamic covalent bond exchange. However, the underlying physics of the transition from thermoplastic to thermoset properties is rather unclear and the subject of current scientific debate. In this work, we address the questions of what extent the temperature-dependent malleability of vitrimers is reflected in the thermal expansion behavior and, conversely, to what extent the thermal expansion behavior is suited to characterize the respective creep behavior of vitrimers. It will be shown that at least in the case of the used model vitrimer, only the canonical glass transition is able to stop the vitrimer to undergo irreversible shape changes and that the often-discussed topology freezing temperature of vitrimers T_v is purely operational.

中文翻译：

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从热体积膨胀和形状（In）稳定性角度观察 Vitrimer 转变现象

Vitrimer 是共价交联的聚合物，可以由温度触发重塑和回收。远高于标准玻璃化转变温度T _g，它们获得可延展的、类似热塑性塑料的特性；在下面，它们表现为热固性材料。负责的分子机制是通过动态共价键交换实现的。然而，从热塑性到热固性性能转变的基本物理原理尚不清楚，也是当前科学争论的主题。在这项工作中，我们解决了玻璃体的温度依赖性延展性在多大程度上反映在热膨胀行为中的问题，以及相反，热膨胀行为在多大程度上适合表征玻璃体各自的蠕变行为。将表明，至少在使用的模型 vitrimer 的情况下，只有规范玻璃化转变能够阻止 vitrimer 经历不可逆的形状变化，并且经常讨论的 vitrimer 拓扑冻结温度T _v纯粹是可操作的。