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