Question

What are micelles? Give an example of a micellers system.

Answer 1

Hint: Generally, in a soap or detergent solution, when a fixed temperature and concentration is achieved, constituent molecules start forming aggregates which usually enhance the properties of that compound.

Complete step by step answer: Micelles are basically aggregating or assembly of many molecules of surfactants which are found dispersed in colloidal solutions. In an aqueous solution, micelles are formed by aggregation of hydrophilic molecules or regions (which are in contact with surrounding solvent) with hydrophobic molecules or regions. If we consider the micelle to be a sphere, the hydrophilic molecules are on the outer surface and hence are also called ‘heads’ and hydrophobic molecules are present at the centre and hence are also termed as ‘tails’.
Micelles are formed only above affixed temperature which is known as kraft temperature \[{\text{(}}{{\text{T}}_{\text{k}}})\] and a fixed concentration which is known as critical micelle concentration.
Various factors such as concentration of surfactant, solution conditions, temperature, pH, ionic strength and geometry of surfactant molecules have drastic effects on the shape and size of the micelle.
Formation of micelles is most often seen in soaps and detergents and is responsible for their cleaning action. When critical micelle concentration is reached in surfactants or detergents they start to act as emulsifiers which can cause a normally insoluble compound to dissolve in the given solvent. This occurs because the insoluble species can be incorporated into the micelle core, which is itself solubilized in the bulk solvent. This is also seen in the mechanism of cleaning by detergents.

Note: Formation of micelles is also seen in human systems. It is essential for absorption of fat-soluble vitamins and certain complicated lipids. Bile salts which are formed in the liver and stored and secreted by the gallbladder cause formation of micelles from fatty acids.