Micelles

Micelles form from amphiphilic molecules that contain both hydrophilic and hydrophobic regions.

These molecules, commonly surfactants in soaps and detergents, arrange themselves in water so that hydrophilic heads face the surrounding solvent while hydrophobic tails avoid contact with it, forming micelles.

However, only when the surfactant concentration exceeds a threshold known as the critical micelle concentration or CMC, surfactant molecules form micelles, causing significant changes in the solution's physical properties.

For instance, osmotic pressure levels off because many individual surfactant molecules combine into fewer, larger aggregates.

Molar conductivity also decreases sharply, since charged surfactant molecules become part of large micelles rather than moving freely in solution.

Ionic surfactants typically have higher CMC values than non-ionic surfactants with identical hydrophobic tails.

Micelles can take various shapes. As the concentration increases, ionic micelles can change from spherical to cylindrical due to reduced repulsions between surface head groups. These cylindrical micelles can form hexagonal arrays, which finally lead to the formation of lamellar micelles.