Hydrophobicity-Driven Enhancement of Hydrogen Bonding in Ionic Liquid Hybrid Solvents

Intermolecular interactions play a fundamental role in the properties of materials, including solvents. Yet, the complex interplay between these interactions, specifically hydrophobic interactions and hydrogen bonding (H-bonding), in liquids, such as the emerging class of ionic liquid hybrid solvents (ILHSs), where these interactions coexist, remains to be fully grasped. Understanding these interactions is crucial for designing new ILHSs and optimizing their performance. Here, we used orthogonal techniques to elucidate the interplay between hydrophobicity and H-bonding in ILHSs composed of ionic components, choline and geranate, and a terpenoid molecular solvent. Our findings reveal a counterintuitive strengthening of H-bond networks with increasing molecular hydrophobicity, uncovered through integrated spectroscopic, calorimetric, and DFT analyses. This insight provides a new framework for understanding how molecular-scale hydrophobicity modulates mesoscopic organization in complex fluids and structured solvents, with implications for enhanced nanoscale organization, biologic encapsulation, and the rational design of ILHSs for applications such as catalysis and drug delivery.