Rheology of Vitrimers: A Hybrid Molecular Dynamics-Monte Carlo Simulation Study

Thermoset polymers are classified amongst the most challenging materials to recycle due to the introduction of covalent intermolecular crosslinks that aims to increase strength and stiffness compared to their thermoplastic counterparts. A new class of polymers called vitrimers presents a promising route to achieve recyclability in thermosets by implementing dynamic covalent bonds within the system. In this work, coarse-grained molecular dynamics in conjunction with a Monte Carlo method, will be used as a simulation methodology to model the bond exchanges in these networks. This hybrid technique can detect the glass transition temperature and the topology freezing temperature from both the volumetric and rheological data. The limited frequency range obtained from the rheology simulations will be extended from three to ten orders of magnitude with the aid of the time-temperature superposition principle and will allow capturing the terminal regime of the moduli at low frequencies characteristic of these systems. The temperature dependence of the zero-shear viscosity of the model will be determined and will be linked with the relaxation time of the network. This simulation methodology provides a theoretical basis for the rational design of the thermophysical properties of vitrimers.