Anionic surfactants are surfactants that carry a negative charge (anion) on at least one part of the molecule. Typical anionic surfactants are derivatives of the nonionic alkoxylates, but are not restricted to molecules comprising an alkylene oxide unit. Because of this charge, anionic surfactants are considered to have dispersing properties. This dispersing charge does not, however, suggest that anionic surfactants are only dispersants, as many also have excellent wetting properties.
Typical anionic functional units are sulfate, sulfonate, phosphate, and carboxylate groups. These groups may be attached to the base molecule via a number of reagents and derivatization processes.