From large surfactant micelle to low interfacial tension: A formulation principle applied to polyoxyethylene mono-n-dodecyl ether—hydrocarbon systems

Abstract

This paper presents a method for achieving low interfacial tension in surfactant formulation. Large surfactant micelles of sizes around 100 nm were found in aqueous surfactant solutions yielding ultralow tension between an oil—water interface. The dynamic interfacial tensions of the non-ionic surfactant—hydrocarbon systems were measured as a function of time with a spinning drop apparatus. A series of polvoxyethylene mono-n-dodecyl ethers (C₁₂H₂₆O(CH₂CH₂O)_xH.x = 3—6,8) and a series of hydrocarbons (C₈—C₁₅) were used in the experiments. The surfactant micelle size was measured by the dynamic light scattering technique using an He—Ne laser. At a spinning rate of 2000 rev min⁻¹ and a surfactant concentration of 0.024%, the process of lowering the interfacial tension seems to undergo a diffusion-controlled solubilization mechanism. It is suggested that one way of achieving low interfacial tension is to build up large surfactant micelles which are effective in solubilization, in the surfactant formulation.