The effect of sodium lauryl sulphate, cetrimide and polysorbate 20 surfactants on complex coacervate volume and droplet size.

The effects of sodium lauryl sulphate (SLS), cetrimide and polysorbate 20 surfactants at concentrations below, at and above their critical micelle concentration (CMC) on the complex coacervation of varying concentrations of gelatin and acacia have been described. The overall effect of increasing concentration of SLS was to reduce the weight of coacervate formed. The addition of increasing concentrations of cetrimide produced an increase in the weight of coacervate. The two lowest concentrations of polysorbate 20 produced an increase in coacervate weight while the highest concentration, above the CMC, reduced the coacervate weight. These effects have been explained in terms of shielding of electrostatic attractions between gelatin and acacia polyions by adsorption of ionic and non-ionic surfactant molecules onto the polyions. The addition of surfactants influenced the size distribution of the coacervate droplets that were produced. It is believed that the reduction in interfacial tension by the aggregation of surfactant molecules at the coacervate-equilibrium liquid interface permitted the formation of smaller coacervate droplets.