surfactant

schematic diagram of the emulsion-polymerization methodSchematic diagram of the emulsion-polymerization method. Monomer molecules and free-radical initiators are added to a water-based emulsion bath along with soaplike materials known as surfactants, or surface-acting agents. The surfactant molecules, composed of a hydrophilic (water-attracting) and hydrophobic (water-repelling) end, form a stabilizing emulsion before polymerization by coating the monomer droplets. Other surfactant molecules clump together into smaller aggregates called micelles, which also absorb monomer molecules. Polymerization occurs when initiators migrate into the micelles, inducing the monomer molecules to form large molecules that make up the latex particle.

surfactant, substance such as a detergent that, when added to a liquid, reduces its surface tension, thereby increasing its spreading and wetting properties. In the dyeing of textiles, surfactants help the dye penetrate the fabric evenly. They are used to disperse aqueous suspensions of insoluble dyes and perfumes.

The surface-active molecule must be partly hydrophilic (water-soluble) and partly lipophilic (soluble in lipids, or oils). It concentrates at the interfaces between bodies or droplets of water and those of oil, or lipids, to act as an emulsifying agent, or foaming agent.

Other surfactants that are more lipophilic and less hydrophilic may be used as defoaming agents, or as demulsifiers. Certain surfactants are germicides, fungicides, and insecticides.

Surfactants are used in corrosion inhibition, in ore flotation, to promote oil flow in porous rocks, and to produce aerosols.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Adam Augustyn.