Abstract
The association of ionizable polymers strongly affects their motion in solutions, where the constraints arising from clustering of the ionizable groups alter the macroscopic dynamics. The interrelation between the motion on multiple length and time scales is fundamental to a broad range of complex fluids including physical networks, gels, and polymer-nanoparticle complexes where long-lived associations control their structure and dynamics. Using neutron spin echo and fully atomistic, multimillion atom molecular dynamics (MD) simulations carried out to times comparable to that of chain segmental motion, the current study resolves the dynamics of networks formed by suflonated polystryene solutions for sulfonation fractions 0 ≤ f ≤ 0.09 across time and length scales. The experimental dynamic structure factors were measured and compared with computational ones, calculated from MD simulations, and analyzed in terms of a sum of two exponential functions, providing two distinctive time scales. These time constants capture confined motion of the network and fast dynamics of the highly solvated segments. A unique relationship between the polymer dynamics and the size and distribution of the ionic clusters was established and correlated with the number of polymer chains that participate in each cluster. The correlation of dynamics in associative complex fluids across time and length scales, enabled by combining the understanding attained from reciprocal space through neutron spin echo and real space, through large scale MD studies, addresses a fundamental long-standing challenge that underline the behavior of soft materials and affect their potential uses.
| Original language | English |
|---|---|
| Pages (from-to) | 149-156 |
| Number of pages | 8 |
| Journal | ACS Polymers Au |
| Volume | 4 |
| Issue number | 2 |
| DOIs | |
| State | Published - Apr 10 2024 |
Funding
D.P. gratefully acknowledges DOE grant DE-SC0019284 for support. NSE measurements were carried at ORNL\u2019s spallation neutron source. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The authors kindly acknowledge the use of computational resources provided by NSF MRI-1725573. This work was made possible in part by advanced computational resources deployed and maintained by Clemson Computing and Information Technology. This research used resources at the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under contract no. DE-AC02-05CH11231. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOEs National Nuclear Security Administration under contract no. DE-NA-0003525. The views expressed in this article do not necessarily represent the views of the U.S. DOE or the United States Government. We thank Shalika Meedin for helpful discussions.
Keywords
- dynamics
- exascale computing
- ionomer solutions
- molecular dynamics simulations
- neutron spin echo
- suflonated polystryene