ABSTRACT
The depletion interaction arises whenever a dispersion of colloidal particles exists in equilibrium with a nonadsorbing macromolecular species. These macromole cules can be polymer molecules, micelles or other aggregate structures, or even other small particles. As two colloidal particles approach each other, such as through Brownian motion, the concentration of macromolecules in the gap region is altered relative to the bulk. At small separations, the macromolecules are ex cluded from the gap region, producing a depletion layer. This reduced concentra tion results in a lower osmotic pressure relative to the bulk, and the resulting attraction is termed the depletion force.
