(440b) Rheology of Covalent Adaptive Networks Using a New Computational Technique

We propose a new model to study polymer covalent adaptive networks (CANs) that can be applied to various polymeric systems. In contrast to conventional thermosets, CANs represent a novel class of plastics in which covalent chemical bonds can be efficiently and reliably exchanged between different positions of the polymer network without risking structural damage or permanent loss of material properties. This unique property allows CANs to behave like thermoset resins (show creep and stress-cracking resistance) in condition of slow dynamics and a thermoplastic resin (malleability, flow, and plasticity) in condition of fast dynamics. Due to their novelty, the unique dynamic behavior presented in CANs is not fully understood. In this study, a combination of a coarse-grained molecular dynamics (MD) and Monte-Carlo (MC) simulations is a proposed to mimic the thermodynamics, dynamics, and rheology of a special category of associative CANs, which are known as vitrimers. Results for the statistics of exchanged bonds and their lifetime in the glassy and rubbery regimes will be presented. Furthermore, the nonequilibrium MD (NEMD) simulations will be used to capture the rheology of these network in small to moderate oscillatory shear deformations. The lifetime of bonds and deformation timescale will be utilized as the main factors to establish a linkage between the rheological response of the vitrimer and its microstructure at different temperatures. The simulations presented in this work will provides a guideline for rational design vitrimers with target properties for specific applications.