Surface and thermodynamic properties of p-alkylbenzene polyethoxylated and glycerated sulfonate derivative surfactants

Abstract

The surface and thermodynamic properties of the 19 p- and n-alkylbenzene polyethoxylated and glycerated sulfonate derivatives as nonionic surfactants have been investigated. Surface tension as a function of concentration of the surfactants in aqueous solutions was measured at 25, 35, 45 and 55°C using the spinning-drop technique. From these measurements, the critical micelle concentration (CMC), the surface pressure at CMC, the maximum surface excess concentration, Γ max, the minimum area per molecule at the aqueous solution-air interface, A min, the effectiveness of surface tension reduction, Π CMC, and the efficiency, pC 20 were calculated. The thermodynamic parameters of micellization ( ΔG mic, ΔH mic, ΔS mic) and of adsorption ( ΔG ad, ΔH ad, ΔS ad) for these nonionic surfactants were also calculated. Structural effects on adsorption, micellization and the effectiveness of surface tension reduction are discussed in terms of these parameters.