Abstract:Gemini surfactants contain two hydrophobic groups and two hydrophilic groups, connected by a linkage close to the hydrophilic groups. They are known to have excellent properties, such as lower critical micelle concentration (CMC), greater efficiency in lowering the surface tension of water and the interfacial tension between water and oil, and better solubility in water than conventional monomeric surfactants. There are many studies on the synthesis and properties of anionic and cationic gemini surfactants, but very few on nonionic gemini surfactants. The nonionic gemini surfactants can be divided into two categories: one is the polyethyleneglycol or phenol ether type gemini surfactant, and the other is the sugar-based surfactant. The synthesis technology and the research progress of the different kinds of nonionic gemini surfactants and their properties are reviewed in this paper. The first method is to insert a spacer between two ready-made amphiphilic groups. The nonionic gemini surfactants can also be synthesized in such a way that the spacer is first combined with two hydrophobic chains, followed by two polar groups. Generally, the spacer is the polyoxyethylene or the polyoxypropylene. The third method is to link the raw materials containing two polar groups by the spacer, and to obtain the nonionic gemini surfactant by adding two hydrophobic chains. In the end of the paper, some suggestions on the development of nonionic gemini surfactants are made for the industrialization of the novel gemini surfactants.