Viscosity of aqueous solutions and local microscopic structure

Area of Science:

• Physical Chemistry
• Solution Chemistry
• Materials Science

Background:

• The classification of ions as water structure makers or breakers is an elusive concept.
• This classification, though criticized, is still prevalent in scientific literature.
• The Jones-Dole relation, incorporating the viscosity B coefficient, is central to this classification.

Purpose of the Study:

• To investigate the relationship between the viscosity B coefficient and local structural properties of aqueous solutions.
• To provide a more quantitative basis for understanding solute-ion interactions with water.
• To explore a potential link between the Jones-Dole viscosity B coefficient and solute-water distances.

Main Methods:

• Utilizing neutron diffraction to probe the local structure of solutions.
• Employing computer modeling to simulate and analyze solute-water interactions.
• Analyzing monovalent electrolyte solutions to establish correlations.

Main Results:

• A linear correlation was found between the viscosity B coefficient and the difference in average distances (solute-water vs. water-water).
• This correlation offers a measurable link between bulk viscosity effects and microscopic structural changes.
• The findings provide a potential quantitative basis for the 'structure maker'/'breaker' concept.

Conclusions:

• The viscosity B coefficient can be quantitatively related to local structural parameters in aqueous solutions.
• This study offers a refined perspective on how solutes influence water structure beyond the traditional maker/breaker dichotomy.
• Neutron diffraction and computer modeling are powerful tools for elucidating solute-solvent interactions.