ΓΌ  Mechanism of micelle formation:
An example for micelle is soap solution. Soap is sodium or potassium salt of a higher fatty acid and may be represented as RCOO–Na+. When dissolved in water, it dissociates into RCOO– and Na+ ions. The RCOO– ions consist of two parts - a long hydrocarbon chain R (also called non-polar ‘tail’) which is hydrophobic (water repelling), and a polar group COO– (also called polar-ionic ‘head’), which is hydrophilic (water loving).

The RCOO– ions are present on the surface with their COO– groups in water and the hydrocarbon chains (R) at the surface. But at critical micelle concentration, the anions are pulled into the bulk of the solution and aggregate to form a spherical shape. Thus, a micelle is formed.

Cleansing Action of Soaps: The cleansing action of soap is due to micelle formation. The soap molecules form micelle around the oil droplet in such a way that hydrophobic part is in the oil droplet and hydrophilic part projects out. Since the polar groups (hydrophilic end) can interact with water, the oil droplets are pulled in water and removed from the dirty surface. Thus, soap helps in emulsification and washing away of oils and fats.