What is a surfactant and why is it useful?
In: Chemistry
Surfactants are a special kind of molecule that combines hydrophobic and hydrophilic properties. This is usually fairly large molecule, with one part of it capable of becoming charged (hydrophilic part) and other other being a long hydrocarbon chain (hydrophobic part). These are also called “head” and “tail” for simplicity. In water, these molecules will form a tiny ball (called micelle) and orient themselves in such a way that “heads” are on the outside and “tails” are inside. While micelles are still forming, “tail” portions can “dissolve” some impurities present in water, like dirt or grease particles/droplets and keep these impurities inside. This is what is happening when you are doing laundry – surfactants in laundry detergent will help dissolve dirt from fabric and carry it away.
It reduces surface tension, making a liquid spread more thinly. Making water wetter, so it can get into tiny little places and dissolve contaminants in or on a material. Dish washing liquid is a good example of a common surfactant.
Surfactants can also be used to make a dye run deeper into a material by making it thinner.
They are also used in fire fighting foams and oil dispersal agents.
The name Surfactant is an amalgamation of “Surface Active Agent”. In general, they most often are used to change the surface tension of water. Think about how a paperclip will float on water. The metal is denser than water but not heavy enough to break the surface tension of the water. Add a drop of dish soap, which is about 20ish% surfactant and the paper clip suddenly sinks. The surfactants in the dish soap lowered the surface tension of the water.
Surfactants accomplish all of these interesting properties by having a water-loving(hydrophilic) head of the molecule and a water-hating(hydrophobic) tail of the molecule. This is what allows it to make foams, clean surfaces, and emulsify. There is almost an endless list of applications for surfactants.
Source: I work for a company that makes surfactants.
Some molecules are kinda like magnets. Different parts of the molecules have different charges and they all attract or repel each other. That’s why water forms beads.
Some molecules are kinda like marbles. They don’t have any charges and don’t interact much, if at all. That’s why oil doesn’t form beads.
If you mix some magnets and some beads, the magnets will all attract each other and clump up. The marbles will just sit there and make way for the magnets to clump up. A surfactant is a molecule made up of mostly marbles but has magnets at the end. When you add enough of these, they’ll form balls with the magnet ends pointing outside and the marble ends on the inside. That way you can have little balls of marbles throughout the magnet soup.
Now replace the magnets with water and the marbles with oil, dirt, or any number of things. That’s how soaps work. That’s also why your skin feels dry after you use soap. Your skin has natural oils on it that prevent you from losing too much water. When you use soap, you strip those oils off it.
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