24 August 2012

Science Fridays! Dimethicone

Hi guys! It's Friday and I am fully prepared to blind you with more science!  This weeks chemical du jour is Dimethicone.


Dimethicone is a very commonly used silicone in most beauty products.  It is primarily used in shampoo, due to some very unique chemical properties it possesses. 

Well, molecularly, it is a polymer.  So it has one common subunit that repeats itself ad nauseum to form a loose chain.  The basics of a silicone based chemical is that it contains Silica (Si), and since Dimethicone is also known as Polydimethylsiloxane, it also contains an Oxygen atom (O) and two Methyl groups as a part of the subunit.  


Primarily, Dimethicone is found in shampoo, because it makes hair shiny and smooth.  Essentially, piths in the hair shaft and lifted cuticles are filled in by Dimethicone and it gives the impression of soft, healthy hair.  Most drugstore shampoos are formulated with TONS of these.

Carbon-Silica-Oxygen polymers have very interesting uses and functions.  The primary being lubrication.  I could talk about visco-elasticity, but thats more of an industrial chemical application. Suffice it to say, certain polymers are very flexible in what state of matter they like to be in.  Traditionally, they are considered a liquid, because they like to flow and smooth out.  (See why they're used in cosmetics?) But not always.  Also, Dimethicone is hydrophobic, so it repels water and is resistant to being rinsed out of the hair once in it.  Hence, why it has to be stripped out of the hair after a while due to build up.


Truthfully, I think it depends on the person.  People usually dislike silicones in shampoos and conditioners because they can build up in the hair line or on the face, and if the skin is not exfoliated properly, it can build up on the face and cause milia.  Generally, if I am cleansing my face in the shower, I wait until after I use shampoo and conditioner to prevent leaving excessive residue on my face.  And it seems to control for milia well, especially in combination with a chemical exfoliant (defoliant ? anybody think perhaps we should start a movement using the proper word for this action?)

There are also groups of people... factions, if you will (DIVERGENT FTW!) who think that silicone in the hair is bad for it.  And if you don't have chemically treated hair, I'd be inclined to agree with you.  However, if you have chemically damaged hair, damage can never be fully repaired and the hair can never revert back to its state before being processed.  Silicones, however, give this illusion that the hair is healthy back to the hair.  So - its sort of take it or leave it, in my opinion.  And generally, if you avoid silicones in shampoos and conditions, you should also avoid them in serums and hair oils, because they are loaded with dimethicones as well.

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