Unconventional Structure-Dynamics Coupling in Polyzwitterion- Polyelectrolyte Aqueous Mixtures

The interplay between polyzwitterions (PZs) and polyelectrolytes (PEs) plays a pivotal role in novel materials for advanced technological applications. Here, we introduced deuterated sodium poly(styrene sulfonate) (PSS) into deuterium oxide solutions of poly(3-(2-vinyl-1-pyridiniumyl)-1-propane sulfonate) (P2VPPS) across various concentrations and molecular weights. We probed the structures and dynamics of the mixtures using small-angle neutron scattering, X-ray scattering, and neutron spin echo spectroscopy with contrast matching. Our data exhibit non-monotonic relaxation decay rates, which are inversely proportional to the static scattering intensities. These results can be interpreted using collective dynamics, with mobility functions that scale inversely with the square of the wavevector. We also examined pure P2VPPS solutions, which show similar scaling behaviors. To our knowledge, this behavior has not been previously reported and leads to puzzling diffusive dynamics. To gain further insights, we performed coarse-grained molecular dynamics simulations to reveal PZ–PE complexation and the coupling between their structures and dynamics. This unconventional coupling between structure and dynamics calls for further theoretical developments.