Effects of Homopolymer Additives on Ion Transport and Conductivity in Model Salt-Doped Block Copolymers

Salt-doped block copolymers (BCP) are promising solid electrolytes because of their ionic conductivity and mechanical strength brought by the combination of two distinct polymer microphases. Recent study has shown that the presence of relatively high molecular weight (MW) homopolymer (of the same type as the conductive phase) creates a relatively homopolymer-rich region within the conducting phase and leads to a higher overall ion conductivity. We use coarse-grained molecular dynamics simulations to understand the correlation between distribution of each component and the local transport of ions. The like-like interactions and masses of the nonconducting block monomers are increased to reflect their higher glass transition temperature. We analyze the distribution of homopolymers and ions as a function of homopolymer additive MW and concentration. We also calculate the distribution of ion drift velocity and conductivity for these systems and show that the dynamic behavior of ions depends on their location within the conductive domain.