Anionic emulsifiers are a type of surfactant that can form stable emulsions with oil droplets in an aqueous phase. The molecules of anionic emulsifiers consist of hydrophilic anionic groups (such as carboxylates, sulfonates, and sulfate esters) and lipophilic non - polar groups (such as long - chain alkyl groups and aryl groups). They form a negatively charged molecular film on the surface of oil droplets and utilize electrostatic repulsion to stabilize the emulsion. Common examples include sodium oleate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate. They are widely used in industries such as cosmetics, food, coatings, and medicine. However, attention should be paid to the pH of the system and the compatibility with other surfactants during use to prevent the impact on the emulsification effect.
Compared with non - ionic emulsifiers, anionic emulsifiers have advantages such as a lower critical micelle concentration (CMC), smaller emulsion particles, good mechanical stability of the emulsion, and rarely cause gelation during the polymerization process. Currently, they are widely used.