(untitled) - Sharma, R; Kamal, A; Abdinejad, M; Mahajan, R K; Kraatz, H.-B (Adv. Colloid Interface Sci., 2017)
As well as cationic, anionic and non-ionic surfactants, there are gemini surfactants in which more than one hydrophilic head group and hydrophobic tail group are linked by a spacer located at or near the head groups. See: