The Effect of Vitrification on the Diels-Alder Reaction Kinetics

The thermoreversible Diels-Alder reaction has attracted much attention for thermally reversible network polymerization. To establish this thermoresponsive behaviour, furan and maleimide functional groups are incorporated into polymer network structures. Self-healing materials use the reversibility of the Diels-Alder equilibrium reaction as a means to repair damage upon thermal or mechanical stimulation.
The dynamic reversibility and the reaction kinetics are well established for applications at temperature above the glass transition temperature [1], e.g., elastomers used for self-healing soft robotic applications [2]. In current work, the effect of vitrification on the Diels-Alder reactivity is studied for applications below and around the glass transition temperature, e.g., low-temperature applications or densely crosslinked thermoset materials. The effect of diffusion control on the reaction kinetics is studied for polymer network systems with dynamically reversible furan-maleimide crosslinks. It is shown how the reaction rates decrease upon vitrification, resulting in slower polymerization and limiting final conversion and crosslink density.

[1] M.M. Diaz, G. Van Assche, F.H.J. Maurer, B. Van Mele, Polymer 120 (2017) 176–188.
[2] S. Terryn, J. Brancart, D. Lefeber, G. Van Assche, B. Vandenborght, Science Robotics 2 (2017) 1–12.