How does your hair conditioner work?

The right hair conditioner can make your hair look glossy and bouncy when the wrong one can make it lank and lifeless. What is in them that can make them so different?

No more bad hair days!

Getting the right pH
When considering the question of how hair conditioners work, you first need to know about the structure of hair. Hair is comprised of 3 major layers: the innermost medulla, the cortex and the cuticle, which is made up of overlapping flat cells like fish scales. These are supposed to lie down flat on to create a smooth, sleek layer which is held together by intermolecular forces called hydrogen bonding.

As you may expect, the more hydrogen there is, the greater the hydrogen bonding and thus the more sleek the hair shaft will be. Acids have lots of hydrogen ions, so the scales will stick down better when the hair is acidic (pH<7), therefore conditioners are usually acidic. However, shampooing often removed the hydrogen ions away from the cuticle, so conditioner is often used to bring that all important lustre and shine back into the hair.

A matter of attraction

The effect of cationic surfactants

The next ingredient that is imperative for the detangling aspect of hair conditioner is cationic surfactants (also known as quaterised surfactants). Do not be put off by their fancy name as the way they work is in fact very simple.

Hair is composed of a protein called keratin and keratin has a high percentage of amino acids that have negative charges sticking out. Soap and shampoo contains surfactants that are anionic meaning that they are also negatively charged. These cleaners are very effective at removing dirt and grease but they also remove the natural oils and positive charges from the hair. If conditioner isn’t used after shampooing, hair becomes frizzy where all the negative regions of the hair repel each other and you end up looking like been electrocuted.

However, cationic surfactants counteract this effect and instead, prevent the build up of static electricity. Most hair conditioners usually contain these cationic surfactants, which are positively charged molecules. Thus, when you use your conditioner after shampooing your hair, the positive charged cationic surfactants are attracted to the negative charges in your hair and they are not completed rinsed out with water. When the hair dries, it is coated in a thin film of these cationic surfactants which are attractive to the negative charge regions on the hair shaft, making the hair sleeker, less likely to tangle and more manageable.

Beautiful hair from beautiful science
So in the end, it’s all a matter of electrostatic attraction and hydrogen bonding. Who knew hair conditioner could contain such exciting science?!