Foam formation in aqueous-ethanol system triggered by the ABA triblock siloxane surfactant

Abstract

The foam formation is difficult in aqueous-ethanol mixed system with lower surface tension. In this work, we reported an ABA triblock siloxane surfactant, with A representing the polyoxyethylene (PEO) and B the polysiloxane chain that can reduce the surface tension of ethanol solution and generate stable foam. The siloxane surfactant molecules can adsorb onto the surface of ethanol solutions due to the hydrophobic-oleophobic property. The foam behaviors show slower Ostwald ripening and drainage process in aqueous-ethanol system. The closer arrangement of ABA triblock siloxane surfactant molecules provides higher surface film elasticity for efficient migration during the surface repair process. Our work provided a surfactant to form stable foam without the additional surfactants in the water–ethanol system, and will open an avenue for foam research in mixed systems.