Solvent-induced molecular gel formation at room temperature and the preparation of related gel-emulsions

The gelation behaviors of four recently reported amphiphilic cholesteryl derivatives (1, 2, 3 and 4) have been evaluated. It was found that the gel formation process can be controlled by introduction of water at room temperature. Addition of water to an acetone solution of 4 immediately results in the system becoming turbid, and a gel subsequently forms within a few minutes. Interestingly, 4 is a super-gelator for a mixed solvent of acetone and water at room temperature, in particular when their volume ratio is close to 1:1 at which the critical gelation concentration (CGC) is 0.06% (w/v). It was found that the introduction of water favors the formation of gel networks, and the gel possesses smart and reversible thixotropic properties. FTIR and ¹H NMR spectroscopy confirmed that hydrogen bonding is one of the main driving forces for the gelation of the solvents. XRD demonstrated that 4 self-assembled into a layered structure within the acetone-water mixed solvent gel. Furthermore, 1 and 2 can be used as excellent stabilizers for gel emulsions of alkanes and water. The maximum of the dispersed phase, water, in one of the gel-emulsions can be as high as 97% (v/v).