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

Self-assembled surfactant films at the solid/liquid interface are investigated as a means to impart stability to nanoparticulate suspensions in extreme environments. Resistance to elastic deformation of the surface surfactant structures is proposed as the primary stabilization mechanism. There exists a critical concentration of surfactant, above which, repulsive forces between coated surfaces are measured and particle stability occurs. This concentration does not correspond to the critical hemimicelle concentration or the bulk critical micelle concentration. Instead, it appears during bilayer formation indicating a possible transition of structure. The effect of alkyl chain length, electrolyte concentration, cosurfactant addition, and substrate on this concentration and the magnitude of the repulsive force demonstrates the similarities between the formation of these self-assembled surfactant surface structures and the formation and stability of bulk micelles.