Gel Formation by the Self-Assembly of Small Molecules: Insights from Solubility Parameters

Abstract

Many small molecules can self-assemble into long fibers and thereby gel organic liquids. However, no capability exists to predict whether a molecule in a given solvent will form a gel, a thin solution (sol), or an insoluble precipitate. In this thesis, we build a framework for gelation via a common gelator based on Hansen solubility parameters (HSPs). Using HSPs, we construct 3-D plots showing regions of solubility (S), slow gelation (SG), instant gelation (IG), and insolubility (I) for DBS in different solvents. Our central finding is that these regions radiate out as concentric shells. The distance (R0) from the central sphere quantifies the incompatibility between gelator and solvent. The elastic moduli of the gels increase with R0, while the time to gelation decreases with R0. Our approach can be used to design organogels of desired strength and gelation time by judicious choice of a solvent or a blend of solvents.