Ionomer morphologies

Work by Dan Bolintineanu, Mark Stevens, and Amalie Frischknecht at Sandia to model the structure of ionic aggregates in ionomers, which are polymers with both neutral and ionized segments.

The first figure shows representative snapshots of ionic aggregates in simulations of poly(ethylene-co-acrylic acid) ionomer melts with 10%, 43%, and 100% Li neutralization (left to right). Only H, Li, and O atoms are shown, and all atoms in the same aggregate have the same color. The zoom of the 43% Li system shows the inter-aggregate spacing that yields the ionomer peak in scattering data; the individual aggregate shows an alternating Li (yellow) and O (red) motif, with some hydrogen bonding (H in white). In contrast to the traditional view of spherical ionic aggregates, the simulations show string-like aggregates. The second figure gives more details of the structures as a function of neutralization percentage.