Polar head group to join the first rule is spacer group linking the two hydrophobic chains, then two polar heads Chiga up, usually ethylene oxide or propylene oxide to join method.

• 极性头基加入法则是联接基团先连接两条疏水链，再把两个极性头基加上去，一般是环氧乙烷或者是环氧丙烷加入的方法。