Analysis of the equilibrium and dynamic surface tension of epoxidized soybean oil grafted hydroxyethyl cellulose (H-ESO-HEC) surfactants with different molecular weights were carried out at pH values that ranged from 8 to 13. A variation in the surface activity of the H-ESO-HEC surfactants was found in the premicellar concentration range because of the formation of surface-active premicellar species, depending on the pH and surfactant concentration. The H-ESO-HEC polymeric surfactants displayed excellent surface properties at pH values that ranged from 9 to 10, and the critical micelle concentration decreased with increasing molecular weight, as expected. The adsorption behavior of H-ESO-HEC polymeric surfactants at the air/solution interface was analyzed by using the Ward and Tordai equation. The effective diffusion coefficients of H-ESO-HEC polymeric surfactants increased with pH values, with the exception of pH 13, and also improved with increasing molecular weight. Furthermore, H-ESO-HEC surfactants with higher molecular weights had larger micelles.
