Surfactants, or surface-active agents, are chemical compounds that reduce the surface tension between different substances, such as liquids, gases, or solids. They are amphiphilic in nature, meaning they contain both:
This unique structure allows surfactants to interact with water and oil, making them essential for processes like emulsification and cleaning. Surfactants can diffuse in water and adsorb at interfaces, such as air-water or oil-water boundaries. The hydrophilic head stays in the water phase, while the hydrophobic tail extends into the oil or air.
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The term "surfactant" originates from the phrase "surface-active agent," first used in 1950. Since then, surfactants have become indispensable in products like detergents, emulsifiers, wetting agents, and foaming agents.
When surfactants are added to a solution, they cluster together to form micelles. These micelles work by:
This arrangement helps disrupt the interface between water, oils, and dirt, suspending the dirt particles and making them easier to remove.
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Shapes of Aggregates
The shape of the aggregates—spherical micelles, cylindrical micelles, or lipid bilayers—depends on the balance between the hydrophilic head size and the hydrophobic tail length.
Surfactants are categorized based on the charge of their hydrophilic head group:
Surfactants are versatile and find applications across industries due to their ability to reduce surface tension and enhance interfacial interactions.
Soaps were among the earliest surfactants, derived from glycerides (esters of fatty acids). The hydrolysis of glycerides with sodium hydroxide, known as saponification, produces:
A surfactant (surface-active agent) is a chemical compound that lowers the surface tension between substances such as liquids, gases, or solids. Surfactants have both hydrophobic (water-repelling) and hydrophilic (water-attracting) parts, making them versatile in applications like cleaning, emulsifying, and foaming.
Examples:
In soap, surfactants are molecules derived from fatty acids and alkalis. They reduce the surface tension of water, allowing oils and dirt to mix with water and be washed away. These surfactants have hydrophilic heads that interact with water and hydrophobic tails that attach to oils, breaking them down into smaller droplets. Example in Soap: Soap molecules, like sodium stearate, act as surfactants. They help remove grease and dirt by forming micelles around oily particles.
In the human body, surfactants are essential biological molecules that reduce surface tension in various processes. Example: Pulmonary Surfactants: These are phospholipids and proteins secreted in the lungs to reduce the surface tension of alveoli, preventing lung collapse and aiding in breathing.
A surfactant is both hydrophobic and hydrophilic. It has: