Discovering Cosmetic Science
Chapter 2: Clean Chemistry – The Science Behind Cleansing Products
Published:23 Sep 2020
Edward Rolls, 2020. "Clean Chemistry – The Science Behind Cleansing Products", Discovering Cosmetic Science, Stephen Barton, Allan Eastham, Amanda Isom, Denise Mclaverty, Yi Ling Soong
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I can honestly state that I find surfactants a truly interesting topic for cosmetic science. They are the key ingredients of many core products and, without them, formulating products such as shampoos, body washes, conditioners and many traditional emulsions would be very difficult. As is often the case with science, there is a lot of ‘jargon’ associated with this class of molecules, with many different terms and names, so I will attempt to describe all of this in the simplest terms and show where the different names come from and put them all into context.
We should start with the structure; the simplest way to start is to think of them as a tadpole as illustrated in Figure 2.1. Now, at first glance you may think, what is so extraordinary about this? Indeed, as a simplistic structure this means that there are only two distinct regions, a head and a tail. This, however, is the key to the characteristics of a surfactant molecule. If we start with the head, this is the portion that is water loving (i.e. it wants to be in water); it is therefore water soluble and does not want to be anywhere near oil. For a more scientific definition, the ‘head’ part of the surfactant could be described as follows: