2. Classification by hydrophobic tail chain

As mentioned above, the types of hydrophobic tail chains of surfactants have been relatively limited for a long time. As for the most common alkyl groups, in addition to straight-chain types, they also include branched alkyl groups (such as sodium bis (2-ethylhexyl) succinate sulfonate, AOT) and unsaturated alkyl groups (such as sodium oleate); in addition, there are cyclic, rigid cholesteric skeletons.