Hydrotropy is a phenomenon where the presence of a large quantity of one solute enhances the solubility of another solute. The\r\nmechanism of this phenomenon remains a topic of debate.This study employed molecular dynamics simulation to investigate the\r\nhydrotropic mechanism of a series of urea derivatives, that is, urea (UR), methylurea (MU), ethylurea (EU), and butylurea (BU).\r\nA poorly water-soluble compound, nifedipine (NF), was used as the model solute that was solubilized. Structural, dynamic, and\r\nenergetic changes upon equilibrationwere analyzed to supply insights to the solubilization mechanism.Thestudy demonstrated that\r\nNF and urea derivatives underwent significant nonstoichiometric molecular aggregation in the aqueous solution, a result consistent\r\nwith the self-aggregation of urea derivatives under the same conditions. The analysis of hydrogen bonding and energy changes\r\nrevealed that the aggregation was driven by the partial restoration of normal water structure.The energetic data also suggested that\r\nthe promoted solubilization of NF is favored in the presence of urea derivatives.While the solutes aggregated to a varying degree,\r\nthe systems were still in single-phase liquid state as attested by their active dynamics.
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