The Lowering of Air-Water and Oil-Water Interfacial Tensions by Fluorinated and Ordinary Surfactant Solutions

Abstract

The effect of added long-chain alcohol (cosurfactant) on the surface and interfacial tensions of fluorinated and ordinary surfactant solutions has been studied. When fluorinated cosurfactant was added to aqueous solution of fluorinated ionic surfactant, regardless of the kind of gegenions, low surface tension, 14-15 dyn/cm, appeared. Aerosol OT or suitable nonionic surfactant considerably reduced the interfacial tension until below 2 dyn/cm, because the Hydrophile-Lipophile-Balance (HLB) of the surfactant was optimum. On the other hand, the interfacial tension between oil and aqueous solution containing ordinary normal-chain ionic surfactant with cosurfactant was almost the same as that without it, despite the low surface tension appeared with cosurfactant. Aqueous solution of a mixture of fluorinated and ordinary surfactants spread over oil surface whose surface tension was only 18-20 dyn/cm.