Effect of Structure on Surfactant Properties

Abstract

The surface tension and foaming properties of sodium oleate were altered by adding a large and electronegative moiety bromine, to its unsaturation. These properties were measured and compared to the original oleic soap. It was found that sodium oleate has a lower CMC than both of the brominated surfactants. The bromine moiety slows down the rate of adsorption with the doubly brominated surfactant being the slowest. Foamability of the brominated analogues were not affected, however its foam were found to be less stable. Bromination also caused the coalescence and bursting of large bubbles.

Keywords:

• Brominated surfactants
• foaming properties

Acknowledgments

The authors wish to thank the support from research grant UKM GUP BTK-08-14-306.

Notes

CMC = critical micelle concentration; γ_cmc = surface tension at CMC; pC₂₀ = negative log of the surfactant molar concentration required to reduce the surface tension of the solvent by 20 mN/m; Γ_max = surface excess concentration; mol/cm²; A_min = minimum area per molecule; Ų, CMC/C₂₀ = ratio of CMC to concentration of surfactant needed for a reduction of surface tension of 20 mN/m.