Effects of Ionic Group Distribution on the Structure and Dynamics of Amorphous Polymer Melts

Journal Article · 22 December 2021 · Macromolecules

DOI: https://doi.org/10.1021/acs.macromol.1c02141 · OSTI ID:2299527

Mohottalalage, Supun S. ^[1]; Aryal, Dipak ^[2]; Thurston, Bryce A. ^[3]; Grest, Gary S.  ^[3]; Perahia, Dvora  ^[4]

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1. Clemson University, SC (United States); Clemson University
2. Clemson University, SC (United States); University of Texas at Austin, TX (United States)
3. Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
4. Clemson University, SC (United States)

Ionizable groups tethered to a polymer backbone often associate to form ionic clusters, whose features are determined by the balance of the polymer backbone and electrostatics. These assemblies impact the dynamics of the macromolecules and their ability to transport ions. Here, using fully atomistic molecular dynamics (MD) simulations, we investigate the effects of the distribution of ionizable groups along the polymer backbone on cluster characteristics and the resulting impacts on the structure and dynamics of amorphous polymers. Particularly, we probe polystyrene sulfonates (PSS) with random, precise, and block configurations of the SO₃^– sulfonate groups along the backbone with Na⁺ as the counterion. We find that the distribution of the ionic groups affects the shape and distribution of the clusters as well as the internal packing of the ionizable groups in the cluster and the number of unique chains that participate in each cluster, affecting the structure and the dynamics of the polymers. Furthermore, the signature of ionic clusters, observed in the static structure factor S(q) for all three distributions, is significantly more pronounced for the precise and blocky polymers compared to the random one. Remarkably, we find that the local mobility of the polymer segments is not only affected by the number and size of the clusters but also by the number of polymer chains associated with clusters.

• Research Organization: Clemson University, SC (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: AC02-05CH11231; NA0003525; SC0019284
• OSTI ID: 2299527
• Journal Information: Macromolecules, Journal Name: Macromolecules Journal Issue: 1 Vol. 55; ISSN 0024-9297
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English