Do Molecular Gelators Cluster in Hansen Space?

Abstract

Hansen solubility parameters (HSP) aid in the a priori prediction of which low molecular weight molecules have the potential to act as low molecular weight organogelators (LMOGs) and can immobilize certain liquids. The hydrogen-bonding HSP parameter individually has some predictive capacity on whether a molecule will form a gel, solution, or precipitate in a known liquid; in the case of benzene, gelators with δh > 5 MPa0.5 form gels, while molecules with δh < 10 MPa0.5 gel ethanol. Small molecules, which gel or remain in a solution state tend to cluster in specific regions of Hansen space. Excellent confinement of solutions was observed within a solubility sphere of benzene, ethanol, and acetonitrile. On the basis of the LMOGs selected, both the magnitude and directionality of the vector in Hansen space are important in predicting the gelation capacity (i.e., a gelator tends to gel toluene Δδp < −4 MPa0.5 when combining the role of Δ2δd and Δδp and ignoring Δδh).