Oil-in-oil emulsions are a subclass of colloids, which contain immiscible non-aqueous solvents (oils) as dispersion and continuous medium and stabilized by solid particles or block polymers. Despite their huge potential in water-sensitive chemistry, these systems are relatively less explored. Lack of efficient small molecular surfactant is one reason for the underdevelopment of o/o emulsion. Therefore, designing and executing discrete surfactant molecules that are capable of stabilizing o/o emulsions is important. Amphiphilic molecules are the first choice owing to their different polarity to stabilize the emulsion. Herein, we have demonstrated a facile method to fabricate supramolecular cage surfactants to stabilize oil-in-oil emulsions. The amphiphilic supramolecular Pd2L4-type cage was constructed by self-assembly of cholesterol-ether appended organic ligands with PdII metal ions. The supramolecular cage contains hydrophobic cholesterol groups and hydrophilic ether chains attached to a cationic cage compartment. This brings anisotropic nature to the overall structure and stabilizes organic solvents that are having different polarities. Interestingly, the formation of a stable foam was observed in the cage's DMSO solution, characteristic of a surfactant molecule. In fact, the amphiphilic cage was effective enough to stabilize DMSO-alkane emulsions for a long period. Further, the non-aqueous emulsion is employed to template polymer capsules by polycondensation reaction where one of the monomers is water sensitive.

Oil-in-oil emulsion polycondensation reactions by supramolecular cage surfactant

ACS Spring Meeting 2021

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