Chain Dynamics in Li-neutralized Precise Acid-Containing Polyethylenes

Single ion conductors have the potential for higher transference numbers, improved mechanical stability, and reduced degradation compared to traditional polymer electrolytes. This study investigates the dynamics of Li-neutralized poly (ethylene-co-acrylic acid) ionomers (pnAA), a linear polyethylene backbone where n is the carbon spacing length between pendant acrylic acid groups (p9AA, p15AA, p21AA). Quasi-elastic neutron scattering experiments and atomistic molecular dynamics simulations are used to understand how changing Li neutralization affects ion aggregation and polymer dynamics in these systems. We directly compare the intermediate scattering structure factor derived from experiments and simulations, and determine dynamic properties such as polymer relaxation times and heterogeneity of motion. Neutralizing the precise ionomers with lithium introduces an additional relaxation time as compared with the parent acid copolymer, and slows the primary relaxation of the systems by 1-3 orders of magnitude.