Polyelectrolytes induce water-water correlations that result in dramatic viscosity changes and nuclear quantum effects.
basic_science · Level V
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- Record sourced from PubMed, PMID 32064319.
- Also identified by DOI 10.1126/sciadv.aay1443 and PMC identifier 6989307.
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Abstract
Ions interact with water via short-ranged ion-dipole interactions. Recently, an additional unexpected long-ranged interaction was found: The total electric field of ions influences water-water correlations over tens of hydration shells, leading to the Jones Ray effect, a 0.3% surface tension depression. Here, we report such long-range interactions contributing substantially to both molecular and macroscopic properties. Femtosecond elastic second harmonic scattering (fs-ESHS) shows that long-range electrostatic interactions are remarkably strong in aqueous polyelectrolyte solutions, leading to an increase in water-water correlations. This increase plays a role in the reduced viscosity, which changes more than two orders of magnitude with polyelectrolyte concentration. Using D<sub>2</sub>O instead of H<sub>2</sub>O shifts both the fs-ESHS and the viscosity curve by a factor of ~10 and reduces the maximum viscosity value by 20 to 300%, depending on the polyelectrolyte. These phenomena cannot be explained using a mean-field approximation of the solvent and point to nuclear quantum effects.