Transport of Associated Particles in Polymeric Melts: A Dynamic Bonding Approach

We developed a coarse-grained molecular dynamics simulation model incorporating a dynamic bonding scheme to study the transport properties of associated particles in polymeric melts. In order to mimic the hopping of lithium ions in polymer electrolytes, a probability of breaking a dynamic bond between an associated particle and an active bead along polymer chains, P_break, was introduced to tune the activation energy between bound and unbound states. Both static (Kuhn length of solvated polymer chains, radial distribution functions, and connectivity of associated particles) and dynamic (mean squared displacement, and diffusion coefficient) properties of two classes of macromolecules were studied: a linear chain system with various bending rigidity and a brush system with various architectures. Simulation results show that the diffusion coefficient of associated particles is linearly proportional to P_break, and scales with the diffusion coefficient of polymer chains as D_assoc ~ D_poly^3/2. These results provide insight in understanding the design rules of polymeric materials for solid-state lithium-ion batteries.