Surfactants are a type of chemical substance that can reduce surface tension at the liquid interface and alter the dispersion, wettability, and emulsification of liquids. They are composed of hydrophobic and hydrophilic groups and can form an adsorption layer at the liquid gas or liquid liquid interface.
According to the relative positions of hydrophilic and hydrophobic groups, surfactants can be divided into the following categories:
Anionic surfactants: Hydrophilic groups are anions, such as carboxylates, sulfonates, etc. Common anionic surfactants include sodium dodecyl sulfate (SDS) and sulfate.
Cationic surfactants: Hydrophilic groups are cations, such as amine salts, quaternary ammonium salts, etc. Common cationic surfactants include cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride.
Non ionic surfactants: Without charge, they interact with liquid molecules through hydrogen bonds. Common non ionic surfactants include polyoxyethylene glycol (such as polyethylene glycol) and octanol polyoxyethylene ether.
Anionic and cationic surfactants: They have both anionic and cationic groups and are commonly referred to as amphiphilic surfactants. Common amphiphilic surfactants include sodium dodecyl sulfate diethanolamine salt (SLES) and carnitine.
Synthetic surfactants: Surfactants obtained through chemical synthesis, such as alkylbenzene sulfonates (LAS) and fatty alcohol polyether ether sulfate sodium (AES).
In addition, there is a special class of surfactants called biological surfactants, such as proteins and phospholipids, which are part of the internal molecules of organisms and can regulate the interface properties of cells and tissues in biological processes.
Surfactants are widely used in many fields, including detergents, emulsifiers, wetting agents, foaming agents, anti-static agents, etc. They play an important role in industries such as agriculture, pharmaceuticals, food processing, and petrochemicals.