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Research Highlight

Adding salt controls conformations of polyzwitterions in aqueous solutions

Snapshots of a polyzwitterion chain
Snapshots of a polyzwitterion chain simulated using density functional tight-binding – snapshots show that (a) salt-free dilute solutions stay in a Gaussian coil form and are weakly charged, (b) small amounts of added KBr (≤0.01M) lead to increased Rg and Rh and anti-polyelectrolyte effects, and (c) higher salt concentrations lead to decreased Rg and Rh and polyelectrolyte effects. Potassium binds to the sulfonated groups of the zwitterion monomers leading to conformational changes.

Scientific Achievement

Study demonstrates that controlling the salt concentration is an effective strategy to tune the net charge and coil conformations of polyzwitterions in solutions.

Significance and Impact

Findings will enable the preparation of processable complexes and coacervates based on polyzwitterions.

Research Details

  • Small small-angle X-ray scattering and dynamic light scattering were performed to study the effects of added salt on gyration (Rg) and hydrodynamic radii (Rh) of poly(sulfobetaine methacrylate) in dilute aqueous solutions.
  • Density functional tight binding molecular dynamics simulations were used to examine molecular details of how the polymer chain coils under different salt concentrations.
  • Added salt affects the net charge and screens electrostatic interactions leading to the anti-polyelectrolyte and polyelectrolyte effects (cf. Figure).


Z. Liu, et al., PNAS Nexus 2(7), pgad204 (2023). DOI: 10.1093/pnasnexus/pgad204

Work was performed at the Center for Nanophase Materials Sciences