Surface activity, foam properties and aggregation behavior of mixtures of short-chain fluorocarbon and hydrocarbon surfactants

Surface activity, foam properties and aggregation behavior of a short-chain fluorocarbon surfactant (FS-50), an anionic hydrocarbon surfactant (sodium dodecyl sulfate, denoted as SDS) and FS-50/SDS mixture are systemically studied for the first time in this paper. Surface activity was characterized by surface tension. Foam properties, including foamability and foam stability, of the mixed systems were studied based on the standard Ross-Miles method. The aggregation behavior of the surfactant solution was observed by using cryo-transmission electron microscopy (Cryo-TEM). The results show that FS-50 exhibits good surface activity and foam properties, which reveals that as a kind of environment friendly short-chain fluorocarbon surfactant, FS-50 is a perfect substitute of long-chain ones. Surface activity and foam properties of FS-50/SDS mixed system are enhanced by adding FS-50 and further improved by the increase of FS-50 concentration. The foam properties are enhanced by tightening the arrangement of surface adsorbed molecules at the liquid-air interface. A synergistic interaction exists in the mixture of short-chain FS-50 and SDS, which is produced through microscopic spheroidal-to-wormlike transition. Finally, the macroscopic performance of FS-50/SDS mixed solution is enhanced by the changes of composition and morphology of the adsorbed film layer. This work shows an environmental friendly surfactants mixed system and provides a more comprehensive perceive of the relationship between macroscopic properties and micro-aggregation structure of short-chain fluorocarbon and hydrocarbon surfactants mixed system.