Synthesis and emulsification properties of novel modified polyoxyethylenated stearylamine surfactants

We have prepared a series of novel modified polyoxyethylenated stearylamine surfactants from two polyoxyethylenated stearylamines (415ST, 430ST), maleic anhydride (MA), and sodium hydrogen sulfite. We measured the surface activities of these compounds in terms of their critical micelle concentrations (CMCs), effectiveness at minimizing surface tension (γCMC), surface excess concentrations (ΓCMC), minimum average areas per surfactant molecule (ACMC), and standard free energies of micellization (ΔGm°). We studied the CMCs of the modified polyoxyethylenated stearylamine derivatives through measurements of their surface tensions, conductivities, and fluorescence (namely, the intensity ratio of the pyrene emissions at 374 and 394nm) with respect to their concentration. In addition, we also studied the surface activity in terms of the emulsification of 10% (w/w) soybean oil in the presence of these surfactants. The smallest emulsion droplets (i.e., the most stable emulsions) were obtained using the modified surfactant 415MA.