Solvotaxis: Gel Motion Against Gravity via Autonomous Solvent Exchange
Year: 2026
Type: preprint
Abstract: Molecular gelation, where a low-molecular-weight gelator (LMWG) self-assembles into a network of fibers, has long obeyed a simple rule: a solvent can be gelled only if the gelator is at least partially soluble in it. In this work, we overturn this paradigm and show that the disaccharidebased gelator 4′,6′-O-benzylidene amygdalin (BA) forms stable gels in solvents where it is completely insoluble. BA dissolves in aqueous media upon heating and forms hydrogels upon cooling, but it is insoluble and does not form gels in oils. When an immiscible nonpolar oil is placed atop a BA hydrogel, the network spontaneously absorbs the oil, expels the water, and migrates upward against gravity. At steady state, a stable BA organogel sits atop liquid water. We refer to this process as Autonomous Solvent Exchange (ASE) and it reveals a strong preference of BA fibers for oil over water (whereas BA molecules prefer water). ASE thus leads to the unusual phenomenon of solvotaxis, i.e., migration of the gel toward its preferred solvent without disrupting the fibrous network. BA organogels with tunable strengths can be formed by solvotaxis across a range of oils (e.g., n-alkanes, natural oils, fuels). Overall, by decoupling molecular solubility from gelation, solvotaxis expands the landscape of gelation to previously inaccessible liquids. Our work also establishes new principles for designing materials that respond autonomously to chemical gradients, with potential applications in environmental remediation and oil recovery.
Source: ChemRxiv
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223028831