(526h) Polymer Dynamics in Block Copolymer Electrolytes Detected By Neutron Spin Echo

Block copolymers have been studied for use in lithium metal solid-state batteries due to their ability to decouple ion transport and mechanical properties. While it is well known that the motion of salt molecules is coupled to that of the polymer segments that solvate the ions, little is known about how the presence of salt affects the dynamics of polymers on longer length-scales. We present results from the first study of polymer chain dynamics in block copolymers (with or without salt) on the 0.1-100 ns time-scale from neutron spin echo spectroscopy experiments. Data were analyzed using the Rouse model at short times (t ≤ 10 ns) and the reptation tube model at long times (t ≥ 50 ns). All of the rich literature on polymer electrolytes is narrowly focused on the transport of ions under small applied fields or in the absence of applied fields. We posit that our measurements of dynamics at long times (50-100 ns) are relevant to the operation of polymer-electrolyte-containing batteries at high currents wherein the diffusion of salt ions in one direction must induce diffusion of polymer chains in the opposite direction.