Micelles and the critical micelle concentration CMC

1
Micelles and the critical micelle concentration
(CMC)

• At low concentrations of soap, surfactant
  molecules exist in solution as monomers
  (individual molecules of surfactant). When a
  hydrophobic dye is added to this solution, the
  dye settles to the bottom and has little
  solubility
• At higher concentrations of soap, the surfactant
  molecules saturate the surface and start forming
  aggregates in solution called micelles (micelles
  are formed once the soap/surfactant exceeds a
  given concentration called the critical micelle
  concentration, CMC). These micelles have a
  hydrophobic (oil-loving) core which can
  solubilize a hydrophobic dye. Thus when the dye
  is added to this solution, it is solubilized and
  results in a vivid change in the color of
  solution.
• This is the same type of mechanism which causes
  detergents and soaps to remove oil and grease
  stains from your dishes or clothes.

2
CMC Explanation
Micelle
Hydrophobic Dye

• The core of a micelle is hydrophobic and can
  solubilize a hydrophobic dye

Micelle Solubilizing Hydrophobic Dye