Anionic surfactants are a class of surfactants that carry a negative charge at the head of their molecular structure. Their hydrophilic groups typically contain functional groups such as sulfonates (-SO₃^-), sulfates (-OSO₃^-), and carboxylates (-COO^-), while their hydrophobic groups are usually long alkyl chains. These characteristics enable anionic surfactants to dissociate into anions in water, thereby reducing the surface tension of liquids and exhibiting excellent wetting, penetration, emulsification, dispersion, and solubilization properties. Common anionic surfactants include carboxylates, sulfonates, phosphates, and fatty acid ester salts.

Main Types and Representative Compounds

Alkyl Sulfates (AS)

Representative Compound: Sodium Dodecyl Sulfate (SDS), also known as Sodium Lauryl Sulfate (SLS).

SDS is a common anionic surfactant with excellent degreasing and cleaning properties. It is widely used in detergents, cosmetics, and pharmaceutical formulations.

Alkyl Ether Sulfates (AES)

Representative Compound: Sodium Lauryl Ether Sulfate (SLES).

SLES is produced by the ethoxylation of lauryl alcohol. It has good foam stability and mildness, making it commonly used in detergents, emulsifiers, and cleaning agents.

Sulfonates

Representative Compound: Sodium Dodecylbenzene Sulfonate (SDBS).

SDBS is an anionic surfactant with excellent emulsification and foaming properties, widely applied in detergents, cosmetics, and industrial cleaning agents.

Carboxylates

Representative Compound: Sodium Lauroyl Glutamate.

This carboxylate-based surfactant is known for its mildness and good foaming properties, commonly used in cosmetics and skincare products.

Phosphate Esters

Representative Compounds: Mono- and diester phosphate surfactants.

These compounds are typically synthesized from fatty alcohols and phosphoric acid. They exhibit good solubility and emulsification properties, making them widely used in industrial cleaners, emulsifiers, and solubilizers.