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Title: Chain and Ion Dynamics in Precise Polyethylene Ionomers

Journal Article · · Macromolecules
ORCiD logo [1]; ORCiD logo [2];  [2]; ORCiD logo [1];  [3];  [4];  [3]; ORCiD logo [2]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies
  2. Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering, and Dept. of Chemical and Biomolecular Engineering
  3. NIST Center for Neutron Research, Gaithersburg, MD (United States)
  4. NIST Center for Neutron Research, Gaithersburg, MD (United States); Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering
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In this paper, we analyze the dynamics from microsecond-long, atomistic molecular dynamics (MD) simulations of a series of precise poly(ethylene-co-acrylic acid) ionomers neutralized with lithium, with three different spacer lengths between acid groups on the ionomers and at two temperatures. At short times, the intermediate structure factor calculated from the MD simulations is in reasonable agreement with quasi-elastic neutron scattering data for partially neutralized ionomers. For ionomers that are 100% neutralized with lithium, the simulations reveal three dynamic processes in the chain dynamics. The fast process corresponds to hydration librations, the medium-time process corresponds to local conformational motions of the portions of the chains between ionic aggregates, and the long-time process corresponds to relaxation of the ionic aggregates. At 600 K, the dynamics are sufficiently fast to observe the early stages of lithium-ion motion and ionic aggregate rearrangements. In the partially neutralized ionomers with isolated ionic aggregates, the Li-ion-containing aggregates rearrange by a process of merging and breaking up, similar to what has been observed in coarse-grained (CG) simulations. In the 100% neutralized ionomers that contain percolated ionic aggregates, the chains remain pinned by the percolated aggregate at long times, but the lithium ions are able to move along the percolated aggregate. In this work, the ion dynamics are also qualitatively similar to those seen in previous CG simulations.

Research Organization:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC04-94AL85000
OSTI ID:
1574444
Report Number(s):
SAND-2019-12520J; 680416
Journal Information:
Macromolecules, Vol. 52, Issue 20; ISSN 0024-9297
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 18 works
Citation information provided by
Web of Science

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