Surfactant

A surfactant is a type of chemical that can lower the surface tension of a liquid and allow for increased spreadability when acting as a wetting agent. The term surfactant is a shortened form of surface active agent. Surfactants are commonly found in a wide variety of detergents and other cleaning products because their ability to lower the surface tension of water makes molecules slipperier and therefore aids in the removal of oil and grease. Surfactants are also used in many lubricants, herbicides, adhesives, emulsifiers, inks, anti-fogging liquids, and fabric softeners. Natural surfactants can also be found inside the human body, where they play a critical role in supporting the respiratory system. Surfactant found in the lining of the alveoli reduces the surface tension of fluid in the lungs, prevents the alveoli from collapsing, and allows for comfortable breathing. In short, surfactants are important chemicals that are a key part of everyday life.

Background

Surfactants have a unique molecular structure that includes both hydrophilic (water loving) and hydrophobic (water hating) parts. While the hydrophilic part of a surfactant dissolves easily in water, the hydrophobic parts are water insoluble. In terms of molecular structure, surfactants can be thought of as looking somewhat like a matchstick. In this comparison, the head of the matchstick would be the surfactant’s hydrophilic polar head group, while the thin wooden end of the matchstick would be the surfactant’s hydrophobic tail portion. This special structural design allows the molecules of a surfactant to interact with both polar water molecules and nonpolar oil molecules. When they are added to water as part of a detergent or some other type of cleaning product, surfactants form structures called micelles. Micelles are tiny spheres composed of surfactant molecules. Within micelles, the tail portions of the surfactant molecules attract and trap oil molecules, while the head portions suspend the oil molecules in water.

Based on the specific nature of their individual molecular structure, surfactants can generally be divided into one of four different classes. These include anionic, cationic, amphoteric, and non-ionic. Anionic surfactants have negatively charged head groups and are widely used for cleaning purposes. This is because soap and other anionic surfactants are excellent detergents. Cationic surfactants have positively charged head groups and, as a result, are attracted to surfaces that carry a negative charge. Examples of cationic surfactants include hair conditioners and fabric softeners. Amphoteric surfactants have head groups with both negative and positive charges. This type of surfactant is most commonly used in shampoos. Finally, non-ionic surfactants have uncharged hydrophilic head groups. Like anionic surfactants, non-ionic surfactants are widely used in various cleaning products.

Pulmonary surfactant is the most common type of surfactant found inside the human body. Pulmonary surfactant greatly reduces the amount of force required to inflate the lungs and makes breathing much easier than it would be otherwise. This type of surfactant is a naturally occurring substance made of lipids and proteins that reduces the surface tension of fluids found in the lungs and stabilizes the alveoli to ensure smooth, easily maintained respiration.

Overview

The primary identifying quality of surfactant is its ability to mobilize and combine materials like water and oil that are difficult or even impossible to mix under normal circumstances because of their incompatible molecular properties. With the addition of surfactant, the molecular barriers between such materials are broken, the surface or interfacial tension is reduced, and a combined formulation is created. This phenomenon can be easily demonstrated with a paper clip and some water. When placed in water, a paper clip will normally float because of surface tension between the water and the surrounding air. If a surfactant is added to the water, however, the paper clip will sink because the surfactant reduces the surface tension between water and air. This also helps to explain why surfactant is such a useful component of cleaning products. In such applications, surfactant plays a key role in the interaction between dirt and water in the cleaning process. When a detergent or some other surfactant is used for cleaning purposes, it reduces the surface tension between the water and dirt, which in turn helps release the dirt and keep it suspended in the water. Once suspended, the dirt can then be easily rinsed or flushed away.

Surfactant has many other uses beyond functioning as a detergent. This is because the properties of various surfactants also include emulsifying or dispersing power and wetting, foaming, and stabilizing power. As a result of these properties, surfactant is a useful and necessary component of lubricant, toothpaste, shaving cream, facial cream, and a wide range of other home products. The usefulness of surfactant is not limited to home goods, however. It also has a variety of commercial and industrial purposes. Among other things, surfactant is used in metal cleaning, textile processing, agricultural crop maintenance, and oil production. In these and other similar applications, the use of surfactant helps to increase energy efficiency and improve the environmental sustainability of commercial and industrial processes.

The most important function of surfactant, however, is the critical role it plays within the human body. Naturally forming surfactant in the human body is found primarily in the lungs. This type of surfactant is known as pulmonary surfactant. Pulmonary surfactant serves to reduce the surface tension of fluid in the lungs and keeps the small air sacs within the lungs called alveoli stable. More specifically, it prevents the alveoli from collapsing when a person exhales. The production of pulmonary surfactant normally begins during the latter stages of fetal development. In some case, babies born prematurely may lack sufficient pulmonary surfactant and may experience respiratory distress as a result. This condition is known as infant respiratory distress syndrome (IRDS). Premature newborns with IRDS typically require surfactant replacement therapy and may also need to be placed on a ventilator. Adults who suffer traumatic injury, severe septic shock, or tissue destruction can also experience a similar condition called adult respiratory distress syndrome (ARDS) if the lining of the alveoli is damaged and the existing pulmonary surfactant becomes ineffective. This can lead to serious respiratory difficulties that must be treated through surfactant replacement.

Bibliography

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