Understanding Solute-Hydrotrope Aggregation in Aqueous Solutions: A Molecular Dynamics Approach

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry

Background:

• Hydrotropy enhances hydrophobic solute solubility in aqueous solutions via amphiphilic molecules called hydrotropes.
• Understanding hydrotropy mechanisms is vital for designing effective hydrotropes for targeted solutes.

Purpose of the Study:

• Investigate the hydrotropic behavior of 1,2-alkanediols for syringic acid solubility.
• Elucidate the molecular mechanisms governing this hydrotropic interaction using computational methods.

Main Methods:

• Molecular Dynamics (MD) simulations.
• Kirkwood-Buff integrals.
• Solvation free energies.
• Radial distribution functions.
• Hydrogen bonding analysis.

Main Results:

• Solvation free energies confirm thermodynamic favorability of syringic acid solubilization by 1,2-alkanediols.
• MD simulations show high syringic acid-1,2-alkanediol affinity, driven by alkyl chains at low hydrotrope concentrations, increasing solubility with chain length.
• Solubilization mechanism shifts with water concentration; hydrogen bonding becomes dominant, leading to maximum solubility at intermediate hydrotrope concentrations for longer alkyl chains.

Conclusions:

• The study elucidates the dual role of 1,2-alkanediol structure in syringic acid solubility.
• Hydrotrope alkyl chain length and water concentration dictate the dominant solubilization mechanism.
• Findings provide molecular insights for designing novel hydrotropes.