Shear Response of Ionizable Polymer Melts at the Crossover from Ionomers to Polyelectrolytes

Journal Article · Wed Aug 13 00:00:00 EDT 2025 · ACS Polymers Au

DOI:https://doi.org/10.1021/acspolymersau.5c00041· OSTI ID:2999507

Meedin, Shalika ^[1]; Grest, Gary S. ^[2]; Perahia, Dvora ^[1]

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1. Clemson University, SC (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Nonlinear shear response of polymers is affected by inherent barriers for diffusive motion, including entanglements and topology. In ionizable polymers, ionic clusters further constrain the intrinsic dynamics of the polymers, significantly enhancing their viscosity. Here, using fully atomistic molecular dynamics simulations, the nonlinear shear response of ionizable polymers is presented, across the transition from the ionomer regime where distinctive clusters dominate the structure to the polyelectrolyte regime where clusters percolate, in polystyrene randomly sulfonated with fractions of SO₃⁻ groups of f = 0.20 and 0.35, in pristine and tetrahydrofuran (THF) swollen polyelectrolyte melts. For f = 0.20, the ionic clusters first fracture into smaller clusters followed by splitting into individual ionic groups and eventually reform. At higher f, the clusters morph in shape but do not break under high shear. At very high shear rates, all of the chains stretch and recoil rapidly. As the shear rate is reduced, some chains stretch and recoil, while others remain largely unaffected by the shear. Macroscopically, for all systems, the shear viscosity displays initially an elastic response, followed by nonlinear shear stress overshoot and, eventually, a steady state. The evolution of viscosity with time and shear reflects that of the ionizable domains.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); National Energy Research Scientific Computing Center (NERSC)
• Grant/Contract Number: NA0003525; SC0019284
• OSTI ID: 2999507
• Journal Information: ACS Polymers Au, Journal Name: ACS Polymers Au Journal Issue: 5 Vol. 5; ISSN 2694-2453
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

cluster chemistry
ionizable polymers
ionomers
nonequilibrium molecular dynamics
polyelectrolytes
polymer tumbling
polymers
shear response
viscosity