Effect of Dynamic Bond Exchange on Thermal Transport and Mechanical Properties of DGEBA/AFD Vitrimers: A Reactive GRRM/MC/MD Simulation Based on Arrhenius Law.

Vitrimers are a class of dynamic covalent polymers that combine the mechanical stability of thermosets with the reprocessability of thermoplastics, which is enabled by bond exchange reactions. In this study, we investigated the DGEBA/AFD vitrimers using a GRRM/MC/MD reactive simulation to model both crosslinking and bond exchange reactions integrated into the molecular dynamics (MD) method. The GRRM method was first used to calculate the reaction energy and activation enthalpy, which were then incorporated into the MD simulations to reproduce the crosslinking and bond exchange reaction dynamics based on the Arrhenius relationship. Comparative analyses were conducted to assess the structural and thermophysical properties with and without bond exchange reaction, including glass transition temperature (Tg) and Young's modulus. Thermal conductivity was also calculated using Non-Equilibrium Molecular Dynamics (NEMD) simulations. The results show that the Tg of the systems with and without bond exchange reactions are comparable, with only a minor change after 200 bond exchange cycles. Similarly, the thermal conductivity of the system shows negligible change after bond exchange reactions. We also revealed that dynamic bond exchange leads to variation in thermophysical properties and stress relaxation in the deformed materials. The anisotropic thermal conductivity of vitrimers induced by uniaxial deformation was found to be diminished by bond exchange, i.e., thermal conductivity decreased in the stretching direction and increased in the transverse direction. Finally, we demonstrated the pressure relaxation and structural reshaping capabilities, confirming that bond exchange reactions play a critical role in stress dissipation and maintaining the deformed structure.