Dynamics and Mechanical Properties of Hybrid Vitrimer Networks

Vitrimers are associative crosslinked polymer networks that exhibit properties of self-healing, network integrity, solvent resistance, and reprocessability. The presence of dynamic covalent bonds allows these networks to undergo topology alterations by applying stimuli such as heat or deformation. One of the proposed methodologies to improve the mechanical properties of vitrimers and mitigate undesirable creep at low temperatures is to create hybrid networks consisting of both dynamic and permanent covalent linkages. The primary objective is to determine a critical concentration of the dynamic bonds to suppress low-temperature creep while retaining the self-healing and reprocessability of vitrimer networks. We use hybrid Molecular Dynamics – Monte Carlo simulations to study the dynamics of glassy vitrimer networks with varying concentrations of reactive sites by subjecting them to triaxial stretching experiments and comparing their behavior to permanently crosslinked networks. Results show that the networks undergo crazing through the bulk, followed by ultimate failure. The vitrimer networks show a higher strain at fracture than the permanently crosslinked network, and this strain is a direct function of the number of available reactive sites in the network. Furthermore, vitrimer networks under triaxial stress successfully relax stress by means of bond exchange reaction even in the glassy regime.