Surfactants can be classified from different perspectives such as structure, function, and source. In terms of structural classification, they can be classified according to the types of hydrophilic and hydrophobic groups and the overall molecular configuration. This paper introduces the basic structure of surfactants, the types of common head groups and hydrophobic tail chains, and representative special structures.

1. Classification by hydrophilic group

Since the types of hydrophobic groups of surfactants have been relatively single for a long time, the classification according to the types of hydrophilic groups has become the main method for classifying surfactants. According to this method, surfactants can be roughly divided into four categories: anionic surfactants, cationic surfactants, zwitterionic surfactants, and nonionic surfactants.