Effects of Glass Transition Temperature and Homopolymer Additives on Ion Transport in Model Salt-Doped Block Copolymers

Salt-doped block copolymers (BCP) are promising as solid electrolytes because they simultaneously provide ionic conductivity and mechanical strength due to the combination of two distinct polymer microphases. The motion of ions within the BCP electrolyte is correlated with chain segmental motion and glass transition temperature (Tg). Recent work has shown that incorporating a relatively high molecular weight (MW) homopolymer can lead to a relatively mobile homopolymer-rich region within the conducting microphase, resulting in a higher overall ion conductivity. We use coarse-grained molecular dynamics simulations to understand these effects and guide further experimental study. We adjust the Tg difference between phases by varying the monomer interaction parameters and masses. We analyze the distribution of homopolymers with different MWs in the conductive domain at different Tg. We also calculate the ion velocity distribution for these systems and show that the dynamic behavior of ions depends on their location within the conductive domain.