The equilibrium and dynamic surface tension of polymeric surfactants based on epoxidized soybean oil grafted hydroxyethyl cellulose

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.