What Is a Surfactant?

Surfactant is the word that combines the terms "surface active agent". Surfactants or tensides are chemical species that act as wetting agents to lower the surface tension of a liquid and allow for increased spreadability. This can be at a liquid-liquid interface or a liquid-gas interface.

Surfactant Structure

Surfactant molecules are usually organic compounds that contain hydrophobic groups or "tails" and hydrophilic groups or "heads." This allows the molecule to interact with both water (a polar molecule) and oils (which are nonpolar). A group of surfactant molecules forms a micelle. A micelle is a spherical structure. In a micelle, the hydrophobic or lipophilic tails face inward, while the hydrophilic heads face outward. Oils and fats can be contained within the micelle sphere.

Surfactant Examples

Sodium stearate is a good example of a surfactant. It is the most common surfactant in soap. Another common surfactant is 4-(5-dodecyl)benzenesulfonate. Other examples include docusate (dioctyl sodium sulfosuccinate), alkyl ether phosphates, benzalkaonium chloride (BAC), and perfluorooctanesulfonate (PFOS).

Pulmonary surfactant provides a coating on the surface of the alveoli in the lungs. It acts to prevent fluid accumulation, keep airways dry, and maintain surface tension within the lungs to prevent collapse.