Influence of Topological Defects on the Rheology and Dynamics of Vitrimers

Vitrimers are polymeric networks with dynamic associative covalent bonds, which can be reprocessed like thermoplastics yet still retain the beneficial properties of a crosslinked thermoset material. Here, we put forward a hybrid coarse-grained molecular dynamics and Monte Carlo simulations to investigate the rheology and dynamic properties of vitrimers. We explore the effects of polymer chain structures on the stress relaxation and shear viscosity. We find that vitrimers with uniform and random sticker distributions show larger viscosity and longer relaxation time of stress than gradient and blocky distributions. This is attributed to the fact that more loop defects in gradient and blocky distributions accelerate the relaxation of dynamic cross-linked bonds. Consequently, our simulation results provide some guidelines for understanding and controlling the rheology and dynamic properties of vitrimers with various chain structures.