Adsorbed surfactants and polymers are able to modify the interactions between particles and hence the stability of a dispersion. A brief description of stabilization of dispersions by electrical interactions is given, including how addition of electrolyte can lead to both flocculation and coagulation of dispersions. Other forces are also exploited either to stabilize or destabilize dispersions. Steric interactions arise from adsorbed macromolecules; steric repulsion depends on the surface concentration of polymer, and also on whether the medium is a good or a poor solvent for the polymer chains. In dilute solutions of polymer that can adsorb simultaneously on two or more particles, bridging can lead to flocculation. Non-adsorbed (free) polymer molecules in solution give rise to depletion forces that result from the exclusion of polymer molecules from between particles in close proximity, which can cause flocculation of dispersions.
Tuning the Properties of Active Microtubule Networks by Depletion Forces