Interaction between emulsion droplets in the presence of polymer-surfactant complexes

Abstract

The interaction between liquid-liquid dispersion covered with polymer-surfactant complexes has been in investigated. The polymer used for our investigations is poly(vinyl alcohol) and the surfactants were sodium dodecyl sulfate, cetyltrimethylammonium bromide and tetradecyltrimethylammonium bromide, and nonyl phenol ethoxylate (NP10). It has been found that the magnitude and the onset of repulsive forces increase dramatically during the association process. The onset of association depends on the nature of surfactant and interfacial properties of the emulsion droplet. The force profiles follow an exponential scaling with a characteristic decay length equal to the R_g of the polymer, irrespective of the surfactant concentration. No associative behavior has been observed in the presence of nonionic surfactant (NP10). The experimental observations suggest that in the presence of charged surfactant molecules or micelles, the neutral polymer chains at the interface are converted into partial polyelectrolytes, where the charges on the chain repel each other and the electrostatic repulsion collectively leads to chain stretching, which would provide better stability to the colloidal particles.