micel

Micel, a term sometimes used for micelle, refers to an aggregate formed by amphiphilic molecules in solution. In aqueous media, surfactant molecules self-assemble into micelles when their concentration rises above the critical micelle concentration (CMC).

A micelle typically features a hydrophobic core formed by the tails and a hydrophilic shell formed by the head groups facing the water. Spherical micelles are common, but under certain conditions they can become rod-like, lamellar, or worm-like, depending on surfactant structure and concentration.

The CMC and micelle size depend on the chemical nature of the surfactant, temperature, electrolyte presence, and pH. Ionic surfactants tend to have higher CMC values that decrease with added salt; nonionic surfactants are less sensitive to ionic strength.

Functions and applications include solubilization of hydrophobic compounds, detergency, emulsification, and stabilization of cosmetic and pharmaceutical formulations. In drug delivery, polymeric or lipid-based micelles can encapsulate poorly water-soluble drugs, enhancing bioavailability.

Analytical methods used to study micelles include surface tension measurements to determine the CMC, dynamic and static light scattering for size, small-angle X-ray or neutron scattering for structure, and cryo-electron microscopy or NMR for detailed morphology.