In 1940, DuPont of the United States developed such compounds and reported the betaine series of amphoteric surfactants for the first time. Since the natural betaine molecule does not have a long enough hydrophobic group and lacks surface activity, it has surface activity only when one of the methyl groups is replaced by a long-chain hydrophobic group. At present, betaines with surfactant properties are generally referred to as betaine series amphoteric surfactants.

Betaine series amphoteric surfactants are amphoteric surfactants containing strongly basic N atoms. They are veritable neutral salts with a wide isoelectric range. They exhibit dipolar characteristics in a wide range. There are many evidences. It is confirmed that the betaine surfactant is in the form of internal salt. Therefore, it is sometimes called quaternary ammonium inner salt surfactant. According to the different negative charge center carriers, the betaine surfactants reported in the current research can be divided into carboxybetaine, sulfobetaine, and phosphobetaine.

Betaine series amphoteric surfactants are neutral salts with a wide isoelectric range, and they exhibit dipolar characteristics in a wide pH range. Due to the presence of quaternary ammonium nitrogen in the molecule, most betaine-type surfactants have good chemical stability in acidic and alkaline media. As long as the molecule does not contain functional groups such as ether bonds and ester bonds, it generally has good oxidation resistance.

Betaine series amphoteric surfactants are easily soluble in water, and can be dissolved in relatively concentrated acids and alkalis and even in concentrated solutions of inorganic salts. They are not easy to interact with alkaline earth metals and other metal ions. Long-chain betaine is easy to dissolve in aqueous medium and is not affected by pH. The solubility of betaine is mainly affected by the number of carbon atoms. The concentration of SX-LAB30 containing lauramidopropyl betaine dissolved in aqueous medium can reach 35%, but the solubility of homologues with longer carbon chains is very low.

The hard water resistance of surfactants is manifested in two aspects: their tolerance to calcium and magnesium hard ions and their ability to disperse calcium soap. Many betaine amphoteric surfactants show very good stability to calcium and magnesium ions. The calcium ion of most sulfobetaine amphoteric surfactants is stable, while the calcium ion stability value of the corresponding secondary amino compounds is Much lower.

Betaine series amphoteric surfactants have rich foaming properties. After being compounded with anionic surfactants, the molecules have strong interactions, and their foaming and viscosity-increasing effects are significantly increased, and the foaming performance of betaine-type surfactants is affected. The water hardness and the pH of the medium have little effect. It can be used as a foaming agent or foam stabilizer and can be used in a wide range of pH.

Betaine series surfactants have very low irritation to the skin and eyes, and are used in cosmetics and detergents. Personal cleansing and care products can effectively reduce the irritation of anionic surfactants such as alkyl sulfates and alkyl ether sulfates.