The structure of Micelle.

Chain molecules such as soap contain hydrophilic (water loving) groups like SO₃H at one end and hydrophobic (water repelling) groups like alkyl groups at the other end. At very low concentrations they do not dissolve in water. Above a concentration called the critical micelle concentration (cmc) the solubility abruptly increases due to the formation of micelles. In a micelle, the hydrophobic groups come together forming a core and hydrophilic groups (which are either charged or dipolar in nature) which are outward are in contact with water molecules. An example of such a structure formed by cetyl trimethyl ammonium bromide (CTAB) is shown in Fig 1.4. It is seen that in the centre of the micelle, a hydrophobic entity has been trapped. Some water molecules which are trapped in the micelle are also shown.