Molecular Dynamics Simulations of Ion-Containing Polymers

Ion-containing polymers are of interest as electrolytes in batteries and as membranes in fuel cells. Designing improved ion-containing polymers requires an understanding of how both polymer architecture and morphology affect ion dynamics. To help build this understanding, we have performed a series of molecular dynamics simulations and connected aspects of these simulations with experiment. In this talk I will describe our recent results on two different systems. The first is a series of precise poly(ethylene-co-acrylic acid) ionomers, which have acid groups precisely spaced along the polymer backbone. Atomistic and coarse-grained simulations of these ionomers show excellent agreement with X-ray scattering data, allowing us to better understand the morphology of ionic aggregates which self-assemble in the ionomers. Recent atomistic MD simulations of these ionomers are in relatively good agreement with quasi-elastic neutron scattering data at short time scales. The comparison with experiment validates the dynamics in the simulations, which we then use to probe polymer and ion dynamics at longer time scales. The second system is a sulfonated poly(phenylene), which conducts protons when hydrated. Atomistic simulations of the structure are in good agreement with X-ray scattering data. I will describe characterization of the morphology using two different clustering algorithms, which may give insights into the proton transport.

Bio:

Amalie L. Frischknecht received her BA in physics and mathematics from Pomona College in 1992 (summa cum laude) and her PhD in physics from the University of California, Santa Barbara in 1998, under an NSF graduate fellowship. She did postdocs at ExxonMobil Research and Engineering (1998-2000) and at Sandia National Laboratories (2000-2003), before becoming a member of technical staff at Sandia in 2003. Dr. Frischknecht is currently a Principal Member of Technical Staff at Sandia National Laboratories, and a staff scientist at the Center for Integrated Nanotechnologies, a DOE Nanoscale Science Research Center and user facility at Sandia and Los Alamos National Labs. She is a Fellow of the American Physical Society. Her research interests are in the statistical mechanics and molecular simulation of complex fluids, including polymer nanocomposites, ion-containing polymers, and charged soft matter systems.