Modeling of\nDiels–Alder Reversible Network\nFormation in Diffusion-Controlled Conditions

A novel mechanistic model is developed for a vitrifying\ncovalent\nadaptable polymer network based on the thermoreversible furan-maleimide\nDiels–Alder (DA) cycloaddition. To account for the effect of\ndiffusion limitations on the reaction rates, a diffusion-controlled\nencounter pair formation mechanism is introduced, with the related\nrates of formation and separation calculated using the Williams–Landel–Ferry\nequation. The kinetic, thermodynamic, and diffusion parameters are\noptimized using calorimetric data and the variation of the glass transition\ntemperature (<i>T</i><sub>g</sub>) with time and/or temperature,\nleading to a set of parameters that can describe a specific thermosetting\nsystem in vitrifying conditions. These parameters are shown to be\nalso valid for a second, chemically similar, reversible network having\na comparable <i>T</i><sub>g</sub>. Lastly, the parameters\nobtained are used to simulate time–temperature-transformation\n(TTT) and continuous-heating-transformation (CHT) diagrams of these\nsystems, including also the vitrified sections. With these results,\nthis model proves to be a versatile tool suitable for the prediction\nof the effect of diffusion limitations for any time–temperature\ncure program, aiding in the accurate interpretation of analytical\nresults related to these reversible networks. This is of particular\ninterest for the design and processing of these self-healing and reprocessable\nmaterials.