Correlation of particulate dispersion stability with the strength of self-assembled surfactant films

Self-assembled surfactant films at the solid/liquid interface are investiga ted as a means to impart stability to nanoparticulate suspensions in extrem e environments. Resistance to elastic deformation of the surface surfactant structures is proposed as the primary stabilization mechanism. There exist s a critical concentration of surfactant, above which, repulsive forces bet ween coated surfaces are measured and particle stability occurs. This conce ntration does not correspond to the critical hemimicelle concentration or t he bulk critical micelle concentration. Instead, it appears during bilayer formation indicating a possible transition of structure. The effect of alky l chain length, electrolyte concentration, cosurfactant addition, and subst rate on this concentration and the magnitude of the repulsive force demonst rates the similarities between the formation of these self-assembled surfac tant surface structures and the formation and stability of bulk micelles.