Ethanol Foams Stabilized by Isobutyl-Based POSS-Organosilica Dual-Particle Assemblies

Nonaqueous foams in low-surface tension solvents (<25 mN·m^-1) are highly desired for applications in fire extinguishers and detoxification gels. However, their formation is a Holy Grail of the chemical industry due to the need for stabilizers with low surface energy and high recyclability. Herein, we disclose a new strategy to generate abundant foams in ethanol and a variety of low-surface tension solvents relying on the interfacial coadsorption of two different particles. The particles consist of surface-active fluorinated silica particles, used as a stabilizer, and a novel amphiphilic polyhedral oligomeric silsesquioxane (POSS) decorated with isobutyl cage substituents, used as a frother. The interaction between POSS and fluorinated particles at the ethanol-air interface was thoroughly investigated by combining physicochemical methods (contact angle, dynamic surface tension, and dynamic light scattering methods) and catalytic tests using the model aerobic oxidation reaction of benzyl alcohol. Both particles could be conveniently recycled for at least 5 consecutive runs with high foamability and catalytic activity.