Surface Tension Study on Aqueous Solution of Nonionic Surfactant with Unsaturated Hydrocarbon Chain

Surface tension measurements were carried out for aqueous solutions of polyoxyethylene oleyl and stearyl ethers with average number of oxyethylene units of 20 (abbreviated as POEOl and POESt, respectively) in order to examine the effect of introducing a double bond into hydrocarbon chain on the surface activity of the surfactants. The overall features of surface chemical properties of these two surfactant solutions are similar to each other, although the surface tension and the critical micelle concentration (CMC) are slightly higher while the amount of surface adsorption is slightly smaller for POEOl compared with those for POESt. Thermodynamic parameters of micelle formation derived from the temperature dependence of the CMC are also close to each other for the two surfactant species. These results demonstrate that the effect of double bond in the surfactant hydrocarbon chain on the surface activity is rather small at least for nonionic surfactant species with relatively long polyoxyethylene chain.