CO2/N2 switchable aqueous foam stabilized by SDS/C12A surfactants: Experimental and molecular simulation studies

A novel CO2/N2 switchable aqueous foam was developed using a CO2-responsive surfactant N,N-dimethyl-N-dodecyl amine (C12A) and a conventional surfactant sodium dodecyl sulfate (SDS). The performance and mechanism of this switchable foam were studied by both experiment and molecular simulation methods. Experimental results demonstrate that the foam stabilized by SDS/C12A surfactants has better stability and water carrying capacity than single C12A foam. The foam could be rapidly switched between stable and unstable states at ambient temperature with CO2 or N2 as the triggers. Simulation results shows that when CO2 was introduced, most of SDS and C12A molecules aggregated in the water phase, instead of adsorbing at the air-water interface to stabilize the foam films. The strong electrostatic attraction between protonated C12A and SDS molecules could account for the aggregation. Due to the presence of limited surfactants located at the air-water interface after introducing CO2, the foam bursts quickly.