DBS-Based Hydrophobic Nonionic Supramolecular Eutectogels: Bridging Molecular Insights to Water Remediation

Supramolecular hydrophobic eutectogels (HEG) are an emerging class of soft materials. They combine the high solvation ability and sustainability profile of hydrophobic eutectic solvents (HES) with the mechanical stability and easy separation and handling of supramolecular gels. However, the relationship between the molecular organization of the HES liquid phase confined within the supramolecular gel, the bulk properties of the gel matrix, and the functional performance of the final material remains largely unexplored. Here, HEG were prepared by self-assembly of the low-molecular-weight gelator 1,3:2,4-dibenzylidene-D-sorbitol (DBS) at two concentrations (2 and 5 wt%) in four nonionic HES (trioctylphosphineoxide:DL-menthol, trioctylphosphineoxide:dodecanoic acid, DL-menthol:oleic acid, and octanoic acid:dodecanoic acid). The HEG were investigated by a combination of rheology, high-resolution magic-angle spinning (HRMAS) NMR spectroscopy, and diffusion measurements, providing a comprehensive description of the materials covering mechanical properties, molecular organization, and translational mobility under confinement. Their potential as economically and environmentally sustainable sorbents in water remediation was demonstrated in the removal of bisphenol A (BPA) from aqueous solutions. The extraction efficiency and cross-contamination arising from HEG component leaching were shown to depend on the interplay between HES-specific intermolecular interactions and DBS-induced confinement. Indeed, the supramolecular organization induced by the gelator introduces an additional level of control over molecular mobility, thus affecting both BPA uptake and leaching. Among the investigated systems, trioctylphosphineoxide-based HEG provided the most favorable balance between BPA removal and leaching of the HEG components, while maintaining their structural and molecular properties after extraction. BPA extraction efficiencies above 98.5% were achieved for the systems containing 5 wt% DBS after 16 h, while quantitative NMR analysis showed low leaching of HEG components (<0.3 wt%). These findings support HEG as versatile materials where molecular organization and mobility, mechanical properties, and pollutant affinity can be tailored to design functional soft materials for separation processes and beyond.