Surfactant (Surface Active Agents)

Surfactant (surface active agents), substances that can activate the surface, because it tends to be concentrated on the surface or interface. Surfactants have a clear orientation that tends to the straight chain. Soap is one example of the surfactant. Surfactant molecule has two separate ends, ie tip of a polar (hydrophilic) and the non-polar (hydrophobic). Surfactants can be classified into two major groups, surfactants are soluble in oil and water-soluble surfactant.

1. Surfactants are soluble in oil

There are three included in this class, namely the long chain polar compounds, fluorocarbon compounds, and silicon compounds.

2. Surfactants are soluble in water solvent

This group is widely used among others as a wetting agent, foaming agent, emulsifier, anti-foam agents, detergents, flotation agents, corrosion prevention, and others. There are four that are included in this class, namely the negatively charged anion surfactant, a positively charged surfactant, surfactant nonion are not ionized in solution, and amphoteric surfactants are negatively charged and positively dependent on pH.

Surfactant lowers the surface tension of water to break hydrogen bonds on the surface. This is done by putting the heads hidrofiliknya on the surface of the water with outstretched hydrophobic tails away from the water surface. Soap can form micelles (micelles), a soap molecule contains a long hydrocarbon chain plus a tip of the ion. Hydrocarbon part of the soap molecules are hydrophobic and insoluble in non-polar substances, while the hydrophilic end of the ion and water soluble. Because of the hydrocarbon chain, a molecule of soap as a whole is not completely soluble in water, but can easily be suspended in the water.


Solution Containing Surfactant properties
Surfactant solution in water showed an abrupt change in physical properties in a particular area of ​​concentration. Abrupt change is caused by the formation of aggregates or clumping of some surfactant molecules into one, namely the concentration of micelles critique (CMC).
Critical micelle concentration occurs on the clumping or aggregation of surfactant molecules form micelles. Micelles usually consist of 50 to 100 molecules of fatty acid soap colloidal properties of electrolyte solutions dedosil sodium sulfate.
There are several factors that affect the value of cmc, for homologous series of hydrocarbon chain surfactant, cmc value increases with reduced single 2x C atoms in the chain. Aromatic group in the hydrocarbon chain increases the value of cmc and also increase the solubility. The presence of salt lowers cmc value of surfactant ions. Cmc decrease depends only on the concentration of the counterion, ie the greater the concentration the more down-nya.Secara cmc micelles general divided into two, namely: lamellar structure and steric.
CMC Determination Method
Because the cmc of the surfactant molecules clumping occurs, then the method of determining the cmc can use the methods of determining the physical quantity that indicates a change from ideal to nonideal circumstances. Below the cmc the solution to be ideal. While the above cmc the solution is not ideal. Physical quantities that can be used is the osmotic pressure, freezing point of solution, the conducting species or the equivalent conductivity, solubility solubilization, refractive index, light scattering, surface tension and interfacial tension.