A novel mechanistic model is developed for a vitrifying covalent adaptable polymer network based on the thermoreversible furan-maleimide Diels–Alder (DA) cycloaddition. To account for the effect of diffusion limitations on the reaction rates, a diffusion-controlled encounter pair formation mechanism is introduced, with the related rates of formation and separation calculated using the Williams–Landel–Ferry equation. The kinetic, thermodynamic, and diffusion parameters are optimized using calorimetric data and the variation of the glass transition temperature (T_g) with time and/or temperature, leading to a set of parameters that can describe a specific thermosetting system in vitrifying conditions. These parameters are shown to be also valid for a second, chemically similar, reversible network having a comparable T_g. Lastly, the parameters obtained are used to simulate time–temperature-transformation (TTT) and continuous-heating-transformation (CHT) diagrams of these systems, including also the vitrified sections. With these results, this model proves to be a versatile tool suitable for the prediction of the effect of diffusion limitations for any time–temperature cure program, aiding in the accurate interpretation of analytical results related to these reversible networks. This is of particular interest for the design and processing of these self-healing and reprocessable materials.

中文翻译：

---

扩散控制条件下 Diels-Alder 可逆网络形成的建模


基于热可逆呋喃-马来酰亚胺 Diels-Alder （DA） 环加成反应，为玻璃化共价适应性聚合物网络开发了一种新的机理模型。为了解释扩散限制对反应速率的影响，引入了扩散控制的相遇对形成机制，使用 Williams-Landel-Ferry 方程计算相关的形成和分离速率。动力学、热力学和扩散参数使用量热数据和玻璃化转变温度 （T_g） 随时间和/或温度的变化进行优化，从而产生一组可以描述玻璃化条件下特定热固性系统的参数。这些参数也被证明对具有可比 T_g 的第二个化学相似的可逆网络有效。最后，获得的参数用于模拟这些系统的时间-温度-转变 （TTT） 和连续加热-转变 （CHT） 图，还包括玻璃化截面。凭借这些结果，该模型被证明是一种多功能工具，适用于预测任何时间-温度固化程序的扩散限制影响，有助于准确解释与这些可逆网络相关的分析结果。这对于这些自修复和可再加工材料的设计和加工特别有意义。